Post on 17-Mar-2018
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CHAPTER ONE
General Introduction
Increasing numbers of people travel to cold and mountainous regions for work, recreation and
physical activities (e.g. soldiers, mountaineers and skiers) (Young et al. 1998; Oliver et al. 2012). In
such cold and hypoxic climates, accidental hypothermia is a perpetual hazard for casualties of
mountain incidents (Kornberger and Mair, 1996) and is a significant contributor to fatalities (Sallis
and Chassay, 1999; Sharp, 2007). The likelihood of developing a peripheral cold injury (e.g. frost
nip and frost bite) or upper respiratory tract infection (URTI) has been reported to be increased in
mountaineers and individuals exposed to cold and high altitude for prolonged periods (Giesbrecht,
1995; Felicijan et al. 2008; Oliver et al. 2012), however whether acclimatisation to altitude reduces
these risks is unknown. Anecdotal evidence suggests a relationship exists between exertional
fatigue, often experienced during outdoor pursuit activities, and susceptibility to hypothermia
(Thompson and Hayward, 1996; Pugh, 1966; Young et al. 1998). Ultimately, ill health and cold
injury are likely to reduce cognitive function and motor performance (Patil et al. 1995), causing
confusion and lethargy so that the casualty is forced to remain sedentary. Furthermore, loss of
motor control makes it difficult to execute survival procedures (Vanggaard, 1975).
Factors found to alter human thermoregulation and immunity in a cold environment include, but are
not limited to: prolonged exposure to cold-wet conditions (Thompson and Hayward, 1996), hypoxia
(Golja et al. 2004), prolonged fatiguing exercise, sleep deprivation and negative energy balance
(Castellani et al. 1998; Young et al. 1998). Nevertheless, the effect of prolonged (> 2 h) exposure to
cold and hypoxia on thermoregulatory and immune responses remains equivocal (Cipriano and
Goldman, 1975; Blatteis and Lutherer, 1976; Giesbrecht, 1995; Savourey et al. 1997; Gleeson,
2000). Since URTIs are associated with a reduction in the concentration of salivary
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immunoglobulin A (s-IgA) (Gleeson, 2000) and research surrounding the typical mucosal immune
response to cold, with and without hypoxia, is sparse, further investigation in this area is required.
Although mortality rates are relatively low with severe non-trauma related hypothermia (<28°C),
they rise alarmingly with traumatic injury where mortality is 100% at 32°C (Moss, 1986; Jurkovich
et al. 1987). Rescue times for casualties depend on global location and weather conditions. Yet even
where distances are relatively short between emergency services and a casualty (e.g. Scottish
Highlands) the reported times for evacuation are 2.25 h by helicopter and approximately 3.5 h when
individuals are evacuated by others means (e.g. on foot) (Crocket, 1995; Hindsholm et al. 1992).
While superior re-warming methods are available (i.e. forced air warmer, inhalation re-warming)
these require medically trained personnel and a power supply. Therefore, simple methods that
prevent heat loss and promote re-warming that casualties or first-responders can administer
instantly whilst they wait for evacuation will likely reduce hypothermia related fatalities. Current
water and wind-proof survival bags aim to reduce core cooling by decreasing heat loss through
convection and radiation (Light and Norman, 1990), yet accidental hypothermia still affects
approximately 10% of casualties reported in mountainous environments. It is pertinent therefore to
establish an optimal lightweight device to increase the rate of core re-warming compared to
shivering alone (Giesbrecht et al. 1987; Williams et al. 2005).
Given prolonged exposure to cold and/or hypoxia poses detrimental effects to themoregulation and
immune function, it is of benefit for those individuals travelling to high altitudes and low
temperatures to know which self-administering survival product will offer optimal protection
against peripheral and central cold injury if a situation occurred where they were forced to remain
sedentary.
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Thesis objectives
With this information in mind, the objectives of this thesis were to:
I. Determine the effects of acute and prolonged (18 days) exposure to a simulated high altitude
of 4000 m on physiological and behavioural thermoregulation during mild cold exposure.
II. Examine the mucosal immunity responses to acute and prolonged (18 days) exposure to a
simulated high altitude of 4000 m
III. Compare the effectiveness of four field re-warming methods for the treatment of cold
casualties upon thermoregulation and metabolism during a three hour ‘awaiting rescue’
scenario in 0°C following cold water immersion to reduce core temperature to 36°C.
IV. Examine the mucosal immunity response to prolonged cold exposure (0°C) in pre-cooled
casualties.
V. Investigate the efficacy of three field protection methods for the treatment of non-shivering
cold casualties using an in vitro torso model exposed to -18.5°C, 0°C and 18.5°C for four
hours.
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CHAPTER TWO
Literature review
2.1 Ill health in cold and hypoxic environments
2.1.1 Hypothermia
Hypothermia occurs through a combination of increased heat loss and decreased heat production.
Heat loss is often increased in cold air when wet and windy conditions are also present (Thompson
and Hayward, 1996). The majority of accidental hypothermia cases are reported to result from cold-
water immersion or cold-water submersion (Golden et al. 1997), cold-air exposure (Pugh, 1966) or
traumatic injury with haemorrhage (Moss, 1986; Jurkovich et al. 1987). Hypothermia is strongly
related to coagulopathy and shock (Beilman et al. 2009) and it is this ‘triad’ that significantly
contributes to the mortality of trauma patients (Arthurs et al. 2006). Since the term ‘hypothermic’ is
often misleading regarding severity, systems exist to classify the different stages of hypothermia
(Table 2.2).
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Table 2.1. Signs, symptoms and physiological changes associated with progressive hypothermia.
Adapted from Danzl and Pozos, (1994).
Stage of
Hypothermia
Rectal
Temperature (°C) Signs and symptoms
37 Normal rectal temperature
Mild
36 Increased metabolic rate due to shivering
35 Maximum shivering thermogenesis
34 Amnesia and judgement problems
33 Ataxia and apathy
Moderate
31 Shivering stops
30 Possible cardiac arrhythmias
29 Decreasing consciousness
28 Increased sensitvity to ventricular fibrillation
27 Loss of voluntary motion
26 No response to pain
Severe
25 Cerebral blood flow decreased to 30%
of normal
22 Maximum risk of ventricular fibrillation
18 Asystole
2.1.2 Peripheral cold injury
In the instance of peripheral cold injury, manual dexterity is impaired and work capacity
deteriorates (Holmer, 1994). For example, military operations in cold, snowy environments increase
the chances for minor cold injuries that limit military unit effectiveness due to lost man-hours. Cold
weather also increases the difficulty of performing tasks related to eating, drinking, and normal
hygiene. This subsequent inability to protect oneself or practise basic survival skills while awaiting
rescue in a cold environment may increase the likelihood of hypothermia related fatalities.
Peripheral ‘freezing’ cold injuries resulting from acute cold exposure include frostbite and frost-nip.
The milder of the two, frost-nip, is a precursor to frostbite and occurs via skin contact with cold
surfaces. With frost-nip, only superficial skin is frozen and tissues are not permanently damaged.
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Frostbite, on the other hand, develops as a function of the body’s protective mechanisms to
maintain core temperature. Warm blood is shunted from cold peripheral tissues to the core by
vasoconstriction of arterioles that supply capillary beds and venules to the extremities and face,
especially the nose and ears. Frostbite progresses from distal to proximal and from superficial to
deep. As the temperature of these areas continues to decrease, cells begin to freeze. Damage to the
frostbitten tissue is due to electrolyte concentration changes within the cells, resulting in water
crystallization within the tissue (Conway et al. 1998).
Frequent or prolonged exposure to moderate cold has been demonstrated to precipitate or
exacerbate shoulder and extremity pain, respiratory infections (Griefahn, 1995) and the ‘non-
freezing’ cold injuries of chilblains (perniosis) and trench (immersion) foot (Herrington, 1996;
Conway et al. 1998). Muscle and tendon tears may also be more likely in cold environments.
Raynaud’s syndrome and the related white finger syndrome cause severe arterial vasoconstriction
with digital blanching, and severe cases may lead to ulceration and tissue loss (Lloyd, 1994). Any
form of peripheral cold injury may have the potential to inhibit individuals from carrying out simple
behavioural thermoregulatory activities.
2.1.3 Upper respiratory tract infections (URTI)
Upper respiratory tract infection (URTI) is a nonspecific term used to describe acute infections
involving the nose, paranasal sinuses, pharynx, larynx, trachea, and bronchi. Therefore URTI
include, but are not limited to: nasopharyngitis, pharyngitis, laryngitis, tonsillitis, sinusitis and
bronchitis. Upper respiratory tract infections represent the most common acute illnesses evaluated
in the outpatient setting. Viruses cause the vast majority of acute upper respiratory tract infections
(Neemisha et al. 2001; Monto, 2002; Fendrick et al. 2003). The common cold is a viral illness with
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the most associated cause being rhinovirus; others are parainfluenza, respiratory syncytial, corona
virus, adenovirus, echovirus, coxsackievirus and parainfluenza virus (Turner, 1995). Rhinovirus
accounts for up to 60% of infections but generally resolves spontaneously without antimicrobial
therapy (Ashes, 1999). Symptoms include nasal discharge, nasal obstruction, and throat irritation.
The National Institute of Allergy and Infectious Diseases reports that people in the USA suffer 1
billion colds each year, with an incidence of two to four for the average adult, and six to ten for
children (Nieman et al. 2011). URTIs impose an estimated $40 billion cost on the US economy
(Fendrick et al. 2003). Lifestyle habits and demographic factors such as mental stress (Cohen,
2005), lack of sleep (Cohen et al. 2009), poor nutrition (Wolvers et al. 2006), and old age (Aw et al.
2007) have all been associated with impaired immune function and elevated risk of infection.
Infections and acute mountain sickness (AMS) are common at high altitude, yet their precise
etiologies remain elusive and the potential for misdiagnosis is considerable (Bailey et al. 2003). The
misdiagnosis of altitude illness is likely due to the similarity of nonspecific constitutional symptoms
(e.g. fatigue, fever, shortness of breath on exertion, decreased appetite and headache) associated
with infection and AMS (Bailey et al. 2003). Both conditions are characterised by changes in
peripheral biomarkers related to free radical, skeletal muscle damage and amino acid metabolism
(Bailey et al. 2003). While not establishing cause and effect, free radical-mediated changes in
peripheral amino acid metabolism, known to influence immune and cerebral serotoninergic
function, may enhance susceptibility to and delay recovery from altitude illness (Bailey et al. 2003).
While AMS is not dangerous, at altitudes over 4000 m it can progress unpredictably to one of two
potentially fatal forms (high altitude pulmonary edema (HAPE) and high altitude cerebral edema
(HACE)) that may co-exist with each other and be misdiagnosed (Wright and Fletcher, 1987).
Symptoms of HAPE include a cough, frothy sputum and lung crackles but without definite
abnormal cardiac signs. These features may be misdiagnosed as pneumonia, which sometimes
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present as an aggravating factor (Wright and Fletcher, 1987). Further, upper respiratory symptoms
(URS) may present in the absence of illness and infection (Giesbrecht, 1995)
2.2 Thermoregulation in cold
During thermoregulatory homeostasis human core temperature (Tc) is maintained close to 37°C
(Widmaier et al. 2004). The central control mechanism in the hypothalamus determines mean body
temperature (Tb) and compares this to a pre-determined set-point temperature by integrating thermal
signals from peripheral and core receptors (Sessler, 1994; Guyton, 1996). Changes in ambient
temperature generate thermo-receptor impulses that are propagated to the anterior hypothalamus via
afferent pathways in the spinal cord (Pocock and Richards, 2006). Efferent responses are mediated
via the posterior hypothalamus to initiate heat loss and heat production mechanisms.
2.2.1 Behavioural responses
Behavioural responses to an increased perception of cold include wearing extra clothing, closing an
open window and turning up the heating. During outdoor pursuits in cold, mountain regions
individuals will often seek cold and wind-proof shelters to make a hot drink or meal. If shelter is
unavailable or stopping is not an option, increasing the intensity of any physical activity or exercise
will help to increase heat production.
2.2.2 Physiological responses – Heat balance
The mechanisms of heat transfer include evaporation, radiation, convection and conduction. Each
mechanism contributes proportionally to heat transfer and fluctuates depending on the air/water
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temperature and humidity. For a healthy human of normal body core temperature in a temperate
environment considered comfortable however, evaporation, the conversion of water to its gaseous
phase, accounts for 20-30% of total body heat loss; radiation, a loss of heat to the environment via
infra-red radiation, accounts for 55-65% of total body heat loss; convection, the transfer of heat to
the external environment by air or water in contact with the body, is accountable for ~12% of total
body heat loss and conduction, the transfer of heat to another object via direct contact accounts for
only 3% of total body heat loss (Kanzenbach and Dexter, 1999).
An involuntary heat transfer response to maintain core temperature in the cold involves the control
of cutaneous vascular smooth muscle tone (e.g. vasoconstriction) combined with a rapid fall in Tsk
(Wagner et al. 1974). This reduced blood flow to peripheral vessels decreases convective heat loss
and conserves Tc. Peripheral vasoconstriction is a powerful mechanism to reduce the heat loss, but
results in strong cooling of the extremities (Daanen, 2003). However, the extremities (i.e. fingers,
hands, ear lobes and toes) possess the ability to prevent the occurrence of local cold extremes with a
specialised pattern of circulation known as arteriovenous anastomoses. These have smooth muscle
in their walls and are deep to the tips of the capillary loops, close to the surface of the skin. The
arteriovenous anastomoses open up when Tb is above normal during reflexively induced
vasodilation and during cold induced vasodilation (CIVD) when Tb is reduced. Upon opening, a
large flow of blood passes through the shunts increasing heat transfer (Abramson, 1967). Since
blood flow increases substantially in the fingers during CIVD, and this increases muscle
temperature and blood circulation in the large vessels of the forearm (Lewis, 1930; Ducharme et al.
1991), it is likely that CIVD reduces the risk of local cold injuries (Iida, 1949; Wilson and
Goldman, 1970), improves manual dexterity and enhances tactile sensitivity during work in the cold
by improving muscle function (Daanen, 2003). Individuals with a higher CIVD response are
considered to be less susceptible to local cold injuries due to the maintenance of a higher rate of
extremity blood flow during cold exposure (Daanen and van Ruiten, 2000).Beyond the specialised
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circulation at the extremities further heat transfer systems exist in the human forearm. Veins
running alongside the ulnar and radial arteries, called venae comitantes (Bazett et al. 1948), create a
counter-current heat exchange system between arteries going to the periphery of a limb and venous
blood returning from the periphery.
2.2.3 Physiological responses – Heat production
In addition to a complex vascular system helping to maintain heat balance in the cold, an increase in
metabolic rate (MR) via shivering thermogenesis (ST) or non-shivering thermogenesis (NST)
evokes heat production and attenuates further decrements in Tc (Lindahl, 1997; Potkanowicz et al.
2003). Consequently, the two main physiological adjustments that occur during cold exposure are
insulative and metabolic (van Ooijen et al. 2004). Nonetheless, such physiological adjustments are
particularly reliant upon individual characteristics given that they may be modified by cold
acclimatisation (Scholander et al. 1958), amount of body fat (Wade et al. 1979), relative humidity
(RH) (Burton et al. 1955), wind speed, physical fitness (Adams and Heberling, 1958; Bittel et al.
1988) and age (Horvath et al. 1955; Wagner et al. 1974).
The level of thermogenesis that humans can achieve and maintain is important for survival during
severely cold weather (Vallerand and Jacobs, 1989). During mild hypothermia (Tc = 35°C) it has
been suggested that ST remains the only physiological process available for maintaining Tc in a
non-exercising casualty void of a re-warming device (Folk, 1974; Neufer et al. 1988; Haman et al.
2002). Metabolic rate, as measured by oxygen consumption (VO2), increases proportionally to
shivering intensity of the whole body or specific muscle groups (Horvath et al. 1956; Tikuisis et al.
1991). Peak shivering intensity can increase heat production up to five times the basal metabolic
rate (BMR) (Eyolfson et al. 2001). The intensity of shivering is determined by the severity of cold
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exposure, the amount of fat-free mass (FFM), the subject’s fitness (Eyolfson et al. 2001) and the
rate of change of the skin temperature (Fiala et al. 2001).
Non-shivering thermogenesis is a heat-production mechanism that involves no muscular
contractions. Heat production under the conditions of basal metabolism is mostly obligatory NST.
Obligatory NST serves to maintain the basic energy demands of the homoeothermic organism
(Jansky, 1973). During cold exposure NST is defined as an increase in heat production in the
absence of shivering (van Ooijen et al. 2005). This additional heat production that occurs is called
regulatory NST (Jansky, 1973).
Non-shivering thermogenesis has been found to occur in the newborn of some species (e.g. humans
and sheep), hibernating animals, and in other animals such as the rat (Horovitz, 1971). Brown fat is
the primary energy source for NST, separating itself from ordinary fat by having much smaller cells
that contain greater amounts of mitochondria (Saito et al. 2009). Studies in animals indicate that
brown adipose tissue (BAT) is important in the regulation of body weight, and it is possible that
individual variation in adaptive thermogenesis can be attributed to variations in the amount or
activity of BAT (van Marken Lichtenbelt et al. 2009). Until recently, the presence of BAT was
thought to be relevant only in small mammals and infants, with negligible physiologic relevance in
adult humans (Astrup et al. 1985; Himms-Hagen, 2001). On the contrary, new evidence has
observed a high rate of occurrence of BAT in healthy young males that is mainly activated during
cold exposure (van Marken Lichtenbelt et al. 2009). The activity of BAT is reported to be greater in
lean males in comparison to those who are overweight or obese (van Marken Lichtenbelt et al.
2009).
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2.3 Thermoregulation in hypoxia
2.3.1 Behavioural responses
Hypoxia has been shown to alter thermal sensation during cold exposure (Golja et al. 2004) which
has been related to a lowered neural activity and delayed signal conduction (Astrup, 1982). This
blunted thermal sensation may cause inappropriate behavioural thermoregulation (e.g. neglecting to
add extra layers of clothing) and therefore be a major implication in cold injury. Anecdotal reports
have also suggested hypoxia alters thermal comfort. However these early reports describe the pain
to single limb, cold water immersion (Mathew, 1979) and thermal discomfort to whole body mild
cold air exposure (Blatteis and Lutherer, 1976) to be greater at altitude than at sea level which did
not abate with altitude acclimatisation (Mathew, 1979; Blatteis and Lutherer, 1976). Further
investigation into the effect of whole body cooling on perception of thermal comfort during acute
hypoxia and following acclimatisation may help provide clarity.
2.3.2 Physiological responses – Heat balance
The effect of hypoxia on typical thermoregulatory responses to the cold remains equivocal. Whilst
some research suggests hypoxia causes greater heat loss and lower core temperatures during cold
exposure compared to normoxia (Cipriano and Goldman, 1975; Kottke et al. 1948, Table 2.2),
other research has reported that hypoxia does not affect thermoregulation (Blatteis and Lutherer,
1976; Robinson and Haymes, 1990, Table 2.2). Those studies that show greater reductions in core
temperature have reported greater increases in skin temperature (Cipriano and Goldman, 1975;
Kottke et al. 1948). Nonetheless, at altitude a significant reduction in CIVD is found where cold co-
exists with systemic hypoxia (Mathew et al. 1977; Daanen and van Ruiten, 2000). Consequently,
the risk for local cold injuries may be enhanced at altitude (Daanen and van Ruiten, 2000).
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2.3.3 Physiological responses – Heat production
It is well established that heat production via the cold-induced increase in VO2 is suppressed during
hypoxia (Blatteis and Lutherer, 1976; Kottke et al. 1948; Savourey et al. 1997) and is coupled with
a reduced time to shivering onset as well as an overall increased shivering intensity (Blatteis and
Lutherer, 1976; Bullard, 1961; Robinson and Haymes, 1990). The occurrence at altitude of a
reduction in the cold-induced increase in VO2 without a diminution of shivering activity suggests
hypoxia depresses NST (Blatteis and Lutherer, 1976) which is related to an inhibition of the aerobic
catabolism of FFA (Robinson and Haymes, 1990). Nonetheless, given the cold-induced increase in
VO2 of high altitude residents has been reported as significantly greater than un-acclimatised
lowlanders, indicates that recovery from the hypoxic depression of the metabolic response to cold
occurs following prolonged exposure to altitude (Blatteis and Lutherer, 1976). However,
acclimatised lowlanders, following a 6 week residence at altitude, showed no reversal in the
hypoxia-induced reduction of the metabolic response to cold. On the contrary, shivering intensity
decreased as altitude exposure continued, yet total VO2 in the cold was not further decreased. This
suggests therefore that some NST recovery may have occurred during the 6-week altitude stay and
helped to replace the reduced ST (Blatteis and Lutherer, 1976).
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2.4 The immune system
2.4.1 Innate immunity - External barriers against infection
The main line of defence from infection is the skin which, when intact, is impermeable to most
infectious agents; when there is skin loss (e.g. burns) infection becomes a major problem (Davies et
al. 2006). Most bacteria fail to survive on the skin because of the direct inhibitory effects of lactic
and fatty acids in sweat and sebaceous secretions and the low pH which they generate.
Mucus secreted by membranes lining the inner surfaces of the body, acts as a protective barrier to
block the adherence of bacteria to epithelial cells. Microbial and other foreign particles trapped
within the adhesive mucus are removed by mechanical stratagems such as ciliary movement and
coughing and sneezing. If microorganisms do penetrate the body, two main avenues of defence
exist to destruct the problem. These are the destructive effect of soluble chemical factors such as
bactericidal enzymes and the mechanism of phagocytosis.
2.4.2 Innate immunity - Phagocytosis
After inoculation, viruses and bacteria encounter several barriers, including physical, mechanical,
humoral and cellular immune defenses. Adenoids and tonsils contain immune cells that respond to
pathogens. Humoral (Immunoglobulin-A) and cellular immunity reduce infections throughout the
entire respiratory tract. Resident and recruited macrophages, monocytes, neutrophils, and
eosinophils coordinate to engulf and destroy the virus or bacteria in the process known as
phagocytosis. A host of inflammatory cytokines mediates the immune response to invading
pathogens. Phagocytic cells have a system of receptors that recognise molecular patterns expressed
by pathogens. Normal nasopharyngeal flora, including various staphylococcal and streptococcal
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species, help defend against potential pathogens. After adherence of the microbe to the surface of
the neutrophil or macrophage the resulting signal initiates the ingestion phase.
2.4.3 Innate immunity - Soluble chemical factors
The spread of infection may be limited by enzymes released through tissue injury which activate the
clotting system. Of the soluble bactericidal substances elaborated by the body, the most abundant
and widespread is the enzyme lysozyme. Like the α-defensins of the neutrophil granules, the human
β-defensins are peptides derived by proteolytic cleavage from larger precursors. The main human β-
defensin (hDB-1) is produced mostly in the kidney, female reproductive tract, oral gingiva and
particularly the lung airways. Another airway antimicrobial active against Gram-negative and
positive bacteria is LL-37.
A number of plasma proteins collectively termed acute phase proteins show a dramatic increase in
concentration in response to early ‘alarm’ mediators such as macrophage derived interleukin-1 (IL-
1) released as a result of infection or injury. It is likely that the acute phase response enhances host
resistance, minimising tissue injury and promoting repair.
2.4.4 Specific acquired immunity – Antibody
Antibodies are an adaptor molecule capable of stimulating the phagocytic cells and sticking to an
invading microbe. Antibodies have three main regions, two concerned with communicating with
phagocytes and one devoted to binding to a microorganism. Each antibody has a recognition portion
complementary in shape to some microorganism to which it can then bind firmly to. The molecules
in the microorganisms which evoke and react with antibodies are called antigens. Each lymphocyte
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of a subset from B-lymphocytes, is programmed to make one antibody on its outer surface to act as
a receptor. When an antigen enters the body it binds to the receptor that it fits best. Lymphocytes,
whose receptors have bound to an antigen receive a triggering signal and develop antibody-forming
plasma cells.
When the body makes an antibody response to a given infectious agent, that microorganism must
exist in the environment and is likely to come into contact again. On first contact with an antigen
the information received imparts some memory so that the body is prepared to repel any later
invasion by that same organism. Upon secondary contact with the antigen the response is
characterised by a more rapid and more abundant production of antibody resulting from the priming
of the antibody-forming system.
2.5 Mucosal immunity
The mucous membranes covering the aerodigestive and urogenital tracts as well as the eye
conjunctiva, the inner ear and the ducts of all exocrine glands are endowed with powerful
mechanisms that degrade and repel most foreign matter (Holmgren and Czerkinsky, 2005). In
addition, a large and specialised innate and adaptive mucosal immune system protects these
surfaces, and thereby also the body interior, against potential insults from the environment. In a
healthy human adult this local immune system contributes to almost 80% of all immunocytes
(Holmgren and Czerkinsky, 2005). The adaptive immune defense at muscosal surfaces is to a large
extent mediated by secretory IgA antibodies, the predominant immunoglobulin in human external
secretions. The resistance of secretory IgA to proteases makes these antibodies uniquely suited for
functioning in mucosal secretions (Holmgren and Czerkinsky, 2005). Although secretory IgA is the
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predominant mucosal defense mechanism, locally produced IgM and IgG can also contribute
significantly to immune defense (Holmgren and Czerkinsky, 2005).
The production of natural antimicrobial peptides (AMP) has emerged as an important mechanism of
innate immunity in plants and animals. Antimicrobial peptides are polypeptides of fewer than 100
amino acids that are found in host defense settings (Ganz, 2003). Cationic antimicrobial peptides,
such as defensins, cathelicidins and thrombocidins, are an important human defense mechanism,
protecting skin and epithelia against invading microorganisms and assisting neutrophils and
platelets (Peschel, 2002). Individual members of these AMP families have been implicated in AMP
activity of phagocytes, inflammatory body fluids and epithelial body secretions. Defensins are
diverse members of a large family of AMPs, contributing to the antimicrobial action of
granulocytes, mucosal host defense in the small intestine and epithelial host defense in the skin and
elsewhere (Ganz et al. 1985; Selsted et al. 1985; Ganz, 2003). Cathelicidins are structurally and
evolutionarily distinct AMPs, similar to defensins in abundance and distribution (Zanetti et al.
1995; Lehrer and Ganz, 2002). Defensins however, are particularly prominent in humans, as
evidenced by the large number of expressed human genes, the various forms that are present in
human tissues, and the ubiquitous occurrence of defensins in inflamed or infected human tissues
(Ganz, 2003).
Saliva is essential for the maintenance of oral health (Mandel, 1989). Saliva flow and composition
function in lubrication, remineralisation, buffering and digestion, while also possessing anti-viral
and anti-bacterial properties (Tenovuo, 1998; West et al. 2006). Saliva is the first line of defense
against pathogens invading the oral cavity (Gleeson, 2000, Table 2.3). The importance of mucosal
secretions cannot be underestimated given that 95% of all infections are initiated at mucosal
surfaces (Bosch et al. 2002). Saliva provides a mechanical washing effect to protect the oral mucosa
whilst mucosal secretions (e.g. immunoglobulins, mucins, amylase, lactoferrin) prevent viral
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replication and bacterial attachment to the mucosal surfaces (McNabb et al. 1981; Mackinnon and
Hooper, 1994; Dowd, 1999).
2.6 Immune system in cold and hypoxia
2.6.1 Cold and immune system
Folklore suggests that exposure to cold ambient temperatures causes humans to contract colds
(rhinoviruses) or other URTI (Dowling et al. 1958; Biggar et al. 1984; Castellani et al. 2002).
However, data to support a link between cold ambient temperatures, reduced immune function and
increased susceptibility to infections in humans is not well delineated (Castellani et al. 2002; Lavoy
et al. 2011). On the contrary, URTI are the most common infections worldwide with peaks often
observed in cold winter months (Mourtzoukou and Falagas, 2007). Furthermore, URTI substantially
increase wintertime morbidity (Hajat et al. 2004) and account for at least 20% of the excess winter
mortality (The Eurowinter Group, 1997; Diaz et al. 2005; Nayha, 2005). Inhalation of cold air and
cooling of the body surface have both been shown to cause pathophysiological responses that may
contribute to increased susceptibility to URTI (Moutzoukou and Falagas, 2007; Giesbrecht, 1995;
Eccles, 2002; Cruz et al. 2006). Albeit, the interaction of exercise and cold exposure on immune
function has not been widely studied (Castellani et al. 2002), data have shown cross country skiers
commonly contract URTIs during outdoor training periods (Bergland and Hemmingsson, 1990).
Secondly, soldiers completing sustained military operations in the Canadian Arctic have displayed
an increased incidence and severity of URTI (Sabiston and Livingstone, 1973). It remains unclear
however, if increased reports of URTI during prolonged cold exposure are due to high levels of
energy expenditure, negative energy balance, cold exposure per se or to a combination (Walsh and
Whitham, 2006).
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Cold exposure has been found to increase plasma nor-adrenaline concentration, a marker of
sympathetic nervous system (SNS) activity (Castellani et al. 2001; Castellani et al. 1999; Castellani
et al. 1998). Since the SNS mediates immune function, exposure to cold may indirectly evoke an
immune response (Castellani et al. 2001). A change in plasma cortisol has demonstrated
modulations in immune function (Shephard, 1997) but at present the effects of cold exposure on
plasma cortisol concentrations remain unclear (Frank et al. 1997; Wilkerson et al. 1974; Wittert et
al. 1992). Nor-adrenaline and natural killer (NK) cell activity have been shown to increase in men
following 30 minutes exposure to 4°C (Lackovic et al. 1988, Table 2.3). However, cell
proliferation decreased after mitogen stimulation in almost identical conditions (Jurankova et al.
1995, Table 2.3). Acute cold water immersion (14°C) demonstrated increased white blood cell
counts (Jansky et al. 1996) and a cold acclimation period with six weeks of cold water immersion,
three times per week increased the percentage of CD14+
and CD25+ cells. Given cold exposure
activates various cellular immune markers, a direct causal relationship to illness or infection
remains unclear. Furthermore, since URS (i.e. persistent dry cough and nasal drying), with the
absence of infection, have been reported following increased ventilation in cold dry air (Giesbrecht,
1995), further studies investigating mucosal immunity during cold exposure may provide some
clarity.
In clinical environments, patients undergoing general anesthetic often experience mild hypothermia
occurring from a reduced ability to produce heat via shivering. This perioperative model of
hypothermia can also be related to a hypothermic casualty in the field who, through additional
trauma, may also be unable to shiver. Perioperative hypothermia is associated with disturbances in
the cardiovascular and respiratory systems, abnormalities in blood coagulation and platelet function,
increased protein catabolism and urinary nitrogen loss following surgery (Forstot, 1995).
Consequently, investigators have reported that hypothermia may delay wound healing and
predispose patients to wound infections (Kurz et al. 1996).
22
In laboratory animals, exposure to hypothermia has been found to enhance the sensitivity of animals
to bacterial infections as compared with normothermic animals (Sheffield et al. 1994). Similarly, in
patients undergoing surgery, mild hypothermia impaired neutrophil oxidative killing during the
intraoperative period (Wenisch et al. 1996). Suppression of immune defense mechanisms occurs in
the postoperative period as a result of surgery stress and anesthesia (Salo, 1992). Such immune
compromise could affect the postoperative infection rate, healing reaction, and the rate and size of
tumor metastases disseminated during surgery (Salo, 1992).
2.6.2 Hypoxia and immune system
Ascent to high altitude is associated with alterations in physiological and metabolic functions
(Mazzeo et al. 1994; Mazzeo et al. 1995; Mazzeo et al. 2001). These adjustments to high altitude
are a necessary attempt to maintain homeostasis in the presence of hypoxemia (Mazzeo, 2005).
However, the sympathoadrenal responses associated with acute and chronic high altitude exposure
can influence immune function which may increase the risk of illness and infection while
individuals are a far distance from appropriate medical resources (Mazzeo et al. 1994; Mazzeo et al.
1995; Mazzeo et al. 2001; Pedersen et al. 1994).). Short term hypoxia has been reported to induce
similar immunosuppression upon the mobilisation of T-cells and natural killer cells (Klokker et al.
1993; Klokker et al. 1995) as that demonstrated during surgery (Lennard et al. 1985) and exercise
(Pedersen et al. 1990). Neutrophil concentration and function changes and the regulation of
cytokine production and release have also been shown to be reduced in hypoxia (Pyne et al. 2000;
Pedersen and Steensburg, 2002).
On the contrary, research remains equivocal regarding the effect of hypoxia on the immune system.
For example, a study examining plasma concentrations of IgG, IgA and IgM were found either
23
unchanged or increased following 40 days between 3200m and 3800m and after two years at an
altitude of 3700m (Meehan, 1987). An earlier investigation comparing the effects of chronic
hypoxia on antibody production of natives from three different altitudes (3051, 3700 and 4680m)
and natives from lower land (150m) (Lopez et al. 1975) found no significant differences between
serum concentrations of IgG, IgA and IgM, albeit there was a tendency for greater IgA values in the
natives from the highest altitude.
2.6.3 Hypoxia and cold and immune system
Given the limited research regarding the immune response to hypoxia, even less information is
available highlighting the immune response to hypoxia in the cold. Nonetheless, it has been
reported that AMS and HAPE are notably more common in mountain climbers during seasons of
lowest ambient temperatures (Giesbrecht, 1995). Furthermore, it is believed that travelling to
regions of high altitude and cold temperatures increases susceptibility to URTI (Walsh and
Whitham, 2006). However, the evidence to support this is lacking and the problem is confounded
by possible misdiagnosis due to some overlap in the symptoms of AMS and URTI (Bailey et al.
2003). On the contrary, it was reported that soldiers stationed at an altitude of 3692m had a higher
prevalence of pneumonia compared with troops stationed at low altitude (Singh et al. 1977).
Anecdotal reports and specific case studies also document an increase in URTI symptoms when
ascending to altitudes >4000m (Basnyat et al. 2001; Oliver et al. 2012).
24
2.7 Mucosal immunity in cold and hypoxia
2.7.1 Cold and mucosal immunity
Stress induced immune perturbations have been attributed to the stimulation of the
sympatheticoadrenal-medullary and hypothalamic-pituitary adrenal axis which cause an increase in
circulating stress hormones (catecholamines and cortisol). An influx of these hormones initiates a
subsequent increase in secretory IgA production (Glesson, 2007). Cold stress is associated with an
increased incidence of bronchorrhea, sinusitis, and other URTI (Clothier, 1974; Giesbrecht, 1995).
Increased ventilation in very cold dry air, due to exercise or increased shivering activity, can cause a
persistent dry cough and nasal drying (Giesbrecht, 1995). Human mucociliary clearance is slowed
on exposure to cold air (Proctor, 1982). This is because the decrease in temperature is likely to
reduce both ciliary beat frequency and the rate of mucus secretion (Proctor, 1982). A large decrease
in temperature is also likely to cause an increase in the viscosity of respiratory mucus. Following a
cross country ski race, a decrease in saliva immunoglobulin-A (s-IgA) concentration was associated
with a large inflow of cold air that lowered the temperature of the mucous membranes (Tomasi et
al. 1982). On the contrary, exercise in the cold has also been found to have no effect on s-IgA
concentration (Housh et al. 1991). However, s-IgA was only reported as a concentration and not
secretion rate, thus ignoring the drying effect of heavy breathing during cold exposure and exercise.
Nonetheless, performing prolonged exercise in freezing cold conditions did not influence saliva
flow rate or s-IgA secretion rate responses (Walsh et al. 2002, Table 2.3). Given research has
investigated mucosal immunity during exercise in the cold, surprisingly little is known regarding
the effects of sedentary activity in the cold upon the mucosal immunity of shivering, cold casualties.
This seems pertinent since heat production arising from shivering activity and subsequent
hyperventilation is similar to that during exercise. Furthermore, since heat production during
25
sedentary activity is eventually outweighed by heat loss, corresponding with a reduction in Tc could
evoke an even larger mucosal immune response.
2.7.2 Hypoxia and mucosal immunity
Mucosal immunity is suggested to be unchanged by hypoxia, and any reduced IgA and lysozyme
levels may be caused by the combined stresses of cold, isolation and reduced humidity (Meehan et
al. 1988; Muchmore et al. 1981). Secondly, given physical activity is often undertaken at altitude
may also inadvertently affect mucosal immunity. For example, individuals enrolled in a ‘live high,
train low’ training camp demonstrated a decline in s-IgA levels, which was suggestive of a
cumulative negative effect of physical exercise and hypoxia on s-IgA (Tiollier et al. 2005, Table
2.3). On the contrary, epidemiologic data has provided indirect evidence that hypoxia may indeed
impair immune competence in humans (Meehan et al. 1988). For example, a higher prevalence of
pneumonia has been found among military troops stationed at high altitude (Singh et al. 1977) and
an increase in infant mortality due to respiratory infections among high altitude natives has also
been reported (Chohan et al. 1975, Table 2.3). Exposure to hypobaric hypoxia therefore, may serve
as a stimulus to activate the neuroendocrine system and identify the mechanisms responsible for
immune modulation during environmental stress in humans (Meehan et al. 1988).
2.7.3 Hypoxia and cold and mucosal immunity
Since URTIs are the main cause of illness and missed practise in elite cross country skiers
(Berglund and Hemmingson, 1990) and cases of acute mountain sickness and high-altitude
pulmonary edema (HAPE) are increased in mountaineers during cold seasons (Giesbrecht, 1995),
26
cold-induced decrements in immune-surveillance may be a potential problem for individuals at
altitude. The additional stressor of cold in hypoxia-exposed humans may evoke a similar
suppression on the mucosal immune system as that demonstrated with physical activity in the cold.
At present, little attention has been directed toward the influence of hypoxia upon mucosal
immunity in the cold. Whether the risk of illness or infection is exacerbated in un-acclimatised
expeditioners upon arrival to hypoxic and cold environments remains unknown. Furthermore, it has
not been clarified whether such detriments to mucosal immunity are reduced following a period of
altitude acclimatisation. This information may have significant implications for spaceflight
personnel during long term missions where conditions of low oxygen supply are likely (Cogoli,
1981; Taylor and Dardano, 1983).
27
28
29
30
2.8 Cold casualty re-warming and protection
The treatment of hypothermia should aim to minimise the post-exposure after-drop and promote a
steady continuous rate of re-warming (Giesbrecht et al. 1997). ‘After-drop’ is the term given when
removal from the cold induces a further reduction in Tc (Giesbrecht and Bristow, 1992) as such re-
warming should be continued until thermal, cardiorespiratory, and metabolic homeostasis can be
maintained (Giesbrecht et al. 1997). One explanation for the after-drop phenomenon is proposed by
the circulatory theory, which has two variations. The first states that upon re-warming, Tc decreases
because of the cold blood returning from vasoconstricted peripheral vessels (Hervey, 1973).
However, it is unlikely that vasoconstriction during cooling would preferentially trap blood
peripherally but rather force it back to the core, leaving minimal blood in these tissues (Giesbrecht
and Bristow, 1992). The second variation is that vasodilation, upon re-warming, results in the flow
of cold blood from the core to previously hypoperfused colder superficial and peripheral tissue,
resulting in further cooling of the blood and subsequently the core (Burton and Edholm, 1955;
Golden, 1973).
Since the movement of cold casualties has been demonstrated to increase after-drop following cold
water immersion (Giesbrecht et al. 1987), after-drop rate may be related to the ambulation of
subjects from a cold to warm environment. For example, core cooling has been measured at 1.2 –
1.3°C/h in subjects buried in snow and wearing only lightweight clothing insulation systems
(Grissom et al. 2004). However, subjects extricated from snow burial after 60 minutes and taken to
a warm environment, displayed a core temperature after-drop rate of 3.3°C/h (Grissom et al. 2008).
The after-drop rate was more than double the core cooling rate, suggesting that movement is a
significant factor of hypothermia severity when indivudals are moved from a cold environment to a
warm environment (Grissom et al. 2010).
31
Currently, most technical re-warming methods for the treatment of hypothermia require
hospitalisation. However, immediate field methods for treating hypothermia occurring during
military operations or outdoor recreation activities are essential when evacuation to hospitals may
be difficult (Giesbrecht et al. 1987). Portable central airway re-warming devices have been
developed for field use (Lloyd, 1973); however these can only be administered by fully qualified
rescue teams. A paucity of information is available for simple, economical and practical re-warming
methods that can be administered by a first responder in the field while awaiting evacuation to
superior means (Giesbrecht et al. 1987).
2.8.1 Hospital based methods
The safety of external whole body re-warming by warm water immersion has created controversy
within the literature. While warm water immersion donates large amounts of heat to promote a rapid
rate of re-warming (Romet and Hoskin, 1988), it causes a large initial Tc after-drop (Hayward et al.
1975) and increases the risk of fibrillation (Webb, 1986). This is because direct warming of the
periphery promotes an increased inflow of cold blood to the heart which creates large core cooling.
Thus, whole body re-warming should not be used with severely hypothermic casualties. By heating
core organs first, (e.g. heating blood in an extracorporeal circuit or peritoneal lavage) after-drop can
be avoided (Webb, 1986). In comparison to warm water re-warming, core temperature after-drop
has been demonstrated to decrease by 30% when forced air warming is used to donate heat by the
direct transfer of warm air onto the periphery of the body (Giesbrecht et al. 1994). On the contrary,
studies investigating the re-warming capacity of inhaling warm, humidified air in mildly
hypothermic subjects removed from the cold have found little (Hayward and Steinman, 1975;
Romet and Hoskin, 1988) or no (Collis et al. 1977; Goheen et al. 1997) benefit compared to
shivering thermogenesis alone. Given perioperative hypothermia may contribute to
32
immunosuppression during the postoperative period, the use of non-invasive re-warming devices
with patients during surgery may help to reduce this.
2.8.2 Field methods
It is acknowledged that mildly hypothermic victims can be suitably re-warmed in the field if
adequate insulation is provided (Pugh, 1964; Grissom et al. 2010). In the field, sources of heat are
limited to the ingestion of warm liquid, body-to-body contact (Harnett et al. 1980; Giesbrecht et al.
1994), heating pads (Collis et al. 1977; Giesbrecht et al. 1987) and possibly inhalation of
humidified air or oxygen (Giesbrecht, 2001). The charcoal burning ‘Heat Pac’ (Heat Pac, Oslo,
Norway) provides a thermal advantage when metabolic heat production is minimal (Hultzer et al.
1999) and is probably the most efficient portable warming device available (Giesbrecht, 2001). It is
small, light and produces approximately 250 W for up to 12 –14 h. Although inhalation warming is
often proposed as an effective strategy for body warming, or at least prevention of further body
cooling (Weinberg, 1998), the advantage regarding thermal balance is minimal (Geisbrecht, 2001).
In shivering subjects, no re-warming advantages were found when re-warming trials were
conducted in 20°C (Romet and Hoskin, 1988), 2°C (Sterba, 1991) or –20°C air (Mekjavic and
Eiken, 1995). When using a human model for severe hypothermia (shivering inhibited by pethidine
in hypothermic subjects) (Giesbrecht et al.1997) inhalation rewarming still did not provide any core
rewarming advantage over spontaneous warming over 150 min of recovery (Goheen et al. 1997).
Early reports suggest body-to-body contact with a minimally clothed euthermic heat donor whilst in
an insulated bag may be beneficial for the re-warming of hypothermic victims (Collis, 1976; Mills
et al. 1987; Robinson, 1992). However, it has been demonstrated that heat donors blunt the
recipients’ shivering thermogenesis and re-warming rates remain the same as that of shivering alone
33
(Giesbrecht et al. 1994, Table 2.4). Therefore, mildly hypothermic victims who are otherwise
healthy and shivering normally should simply be removed from the cold stress to a dry insulated
environment (i.e. a sleeping bag). Victims who are not shivering because of severe hypothermia,
impaired thermoregulatory control, or depleted metabolic substrates should be evacuated to a
medical facility immediately (Grissom et al. 2010). The absence of shivering has been reported to
induce a three-fold increase of Tc after-drop and a four-fold increase in the length of the after-drop
period compared to when shivering is not inhibited (Giesbrecht et al. 1997). However, research is
limited as to the effects of hypothermia on non-shivering casualties due to the ethical boundaries of
injecting subjects with shivering depressants.
An alternative way to increase the body’s own heat production is through exercise. However, after-
drop amount and length were found to be greater in cold individuals during an exercise re-warming
protocol compared to shivering only or externally applied heat (Giesbrecht et al. 1987, Table 2.4).
It is likely that before exercise, blood in the muscles is cooler than blood at the core; nonetheless,
given that exercise increases circulation, blood at the core is readily cooled (Hudlicka, 1982;
Giesbrecht et al. 1987). For this reason exercise should be avoided in an individual whose Tc is
unknown or less than 32°C and shows signs of physical and / or metabolic exhaustion, (i.e.
incapable of shivering). Additionally, through injury, individuals may be forced to remain sedentary
while awaiting rescue.
2.8.3 Single and multi-layer survival products
Metalized plastic sheeting (MPS) is a single layered, water and windproof material thought to
benefit the human body by reflecting radiated heat lost from the body surface (Marcus et al. 1977,
Table 2.4). Single-layer MPS products were originally favoured for their small (e.g. 9.5cm x 2.5cm
34
(folded)), light-weight (e.g. 50g) appeal compared to heavier, bulkier casualty bags made of
materials such as goose down (Light et al. 1980, Table 2.4). However, research to date is equivocal
as to the thermal protection provided by MPS. For example, MPS and metal foil have been
associated with a reduced heat loss in cold conditions (Spencer-Smith, 1977). On the other hand,
MPS has been found to be inefficient at preventing heat loss during operative surgery (Radford and
Thurlow, 1979), and was reported to provide no additional thermal protection to the periphery of
cold exposed humans in comparison to polythene and nylon (Marcus et al. 1977).
Anecdotal reports suggest the light-weight structure and weak adhesive of MPS bags makes them
insecure and easily torn. Yet, bulk and weight of a casualty bag is of direct importance to the
individual who must survive in an isolated environment using only what they may have carried with
them in a rucksack (Light et al. 1980). Single layer MPS may be light-weight but appears to offer
little thermal protection in cold environments. However, placing a fibre pile liner inside a casualty
bag incorporating MPS seems to evoke significantly smaller reductions in Trec and Tsk compared
with single layer MPS (Light et al. 1980). In this study, shivering was also noted to be eliminated in
the MPS and fibre pile bag, indicating multi-layer products may offer thermal and metabolic
advantages. Additionally, multi-layer survival products tested during a one hour cold exposure in -
10°C and average wind speed 3.0m∙s-1
, were able to maintain Tsk close to normothermia, while
single layer MPS was not (Grant et al. 2002, Table 2.4). Despite this, participants reported similar
increased perceptions of cold and displayed a rapid fall in Trec. Each multi-layer system had a wind
and water-proof nylon outer; one contained a fibre pile lining and the other incorporated an inner
Duffel bag. Evidently multi-layer systems may better conserve heat via improved insulation in
comparison to single-layer systems. However, while Tc continues to decline rapidly in currently
available survival products, alternative materials should be researched.
35
Albeit, multi-layer devices may provide initial re-warming treatment to a cold casualty, subsequent
peripheral warming has been reported to evoke a secondary decline in Tc (Grant et al. 2002).
Peripheral vasoconstriction therefore, is likely to be limited in casualties wearing thick winter
garments inside a survival bag because of a high heat transfer generated from the body’s core to the
skin (Grant et al. 2002; Vokac and Hjeltnes, 1981). A temperature gradient between the skin and
the air inside the bag may impair peripheral thermoreceptor activity (Grant et al. 2002). To protect
ecological validity most research with survival products includes participants wearing typical
outdoor clothes (Marcus et al. 1977; Light et al. 1980; Light and Norman, 1990; Grant et al. 2002).
However, this could be causing a temperature gradient within the survival bag and thus contributing
to the observed decline in Tc. At present, the maximal capacity to protect Tc in survival bags
remains unknown. Research should therefore examine multi-layer survival products while subjects
are minimally clad.
A recent in vitro study comparing cooling times of pre-heated fluid bags protected with different
field methods reported that a multi-layered survival bag (Blizzard Survival™) was superior at
preventing core heat loss compared with a polythene survival bag, single layer MPS and wool
blanket (Allen et al. 2010). Further, an active heating combination of the multi-layered metalized
sheeting survival bag (Blizzard Reflexcell™) with chemical heat pads was shown to be superior to
all other methods tested. Nonetheless, given that the exposure conditions did not reflect typical cold
temperatures experienced during outdoor winter pursuits, it remains unknown how well these
devices will protect non-shivering, sedentary humans in the cold.
Reflexcell™ has an elasticised and cellular construction to trap warm air and draw the material to
the body. This reduces the number of cold spaces and heat loss by convection. The silvered surfaces
of Reflexcell™ reduce heat loss by radiation and provide a wet and wind proof layer. Minimising
heat loss by convection and radiation during cold exposure reduces the likelihood of hypothermia
36
(Light and Norman, 1990). The Blizzard Survival™ bag, light-weight and easily compressed in to a
video cassette package, is a full sized sleeping bag constructed entirely from Reflexcell™ material.
The Blizzard Survival Heat™ comprises Reflexcell™ technology with self-activating heat pads
which can also be vacuumed to the size of a video cassette. Self-activating heat pads eliminate the
need for a power supply, and Velcro sides allow medical attention to be administered efficiently.
Thermal efficiency of sleeping bag materials is generally expressed as a warmth-to-weight ratio by
dividing the insulating value of the material (Togs) by the weight of a typical sleeping bag made
from that material. The basic unit of insulation coefficient is the RSI (1m2k/watt). One tog is equal to
0.1 RSI. This means the thermal resistance in togs is equal to ten times the temperature difference
(in °C) between the two surfaces of a material, when the flow of heat is equal to one watt per square
metre. University laboratory tests using a Tog rating of 8 Togs and a weight of 330 g for the
Reflexcell™ bag found a value of 24 Togs/kg. This is over twice the value for goose down, which
was previously regarded as having the highest possible warmth-to-weight ratio among insulating
materials. Further investigation of Reflexcell™ with human participants is required to test the
thermal capacity provided by this new technology.
37
38
39
CHAPTER THREE
General methods
3.1 Ethical approval
Approval for all studies was obtained from the local Ethics Committee (School of Sport, Health and
Exercise Sciences, Bangor University). The nature and purpose of each study was explained both
verbally and in writing to each volunteer (Appendix A). Each participant was made aware that they
were free to withdraw from the study at any time and completed an informed consent form
(Appendix B). All volunteers were non-smokers and had no significant oral, dental, or systemic
disease and were not taking any medication at the time of participating in the studies. To determine
eligibility for inclusion into a research study, participants completed a medical and health
questionnaire (Appendix C) and reported no incidences of illness in the six weeks prior to
beginning the study.
3.2 Anthropometry and body composition
Height was recorded using a wall stadiometer (Bodycare Ktd, Warickshire, UK) and NBM by
digital platform scales accurate to the nearest 50 g (Model 705, Seca, Hamburg, Germany). Whole
body skeletal muscle mass, appendicular lean mass, and fat free mass were assessed using
segmental multiple frequency bioelectrical impedance (InBody 230, Biospace, Seoul, 3 Korea). For
this procedure participants removed shoes and socks and dressed in t-shirt and shorts only. Validity
and reliability of this technique to assess regional and whole body composition has been shown
previously (Malavolti et al. 2003; Jensky-Squires et al. 2008).
40
3.3 Experimental procedures
The day prior to each experimental trial participants ingested water equal to at least 35 ml·kg-1
body
mass and a prescribed diet. Participants arrived to the laboratory euhydrated. This was verified by
urine specific gravity equal to or less than 1.020 g·ml-1
(Casa et al. 2005) and urine osmolality no
greater than 800 mOsm/kg (Urine Osmolality Meter PAL-mOsm). Hydration was also inspected
against a urine colour chart with hyrdration accepted as a level 3 or less (Armstrong, 2000).
3.4 Thermoregulatory measures
Core temperature (Trec) was recorded using a flexible thermistor inserted 12 cm beyond the anal
sphincter (YSI 4000A, Daytona, FL, Chapter 4 and 5) (2020 series, Squirrel data logger, Grant)
(Chapter 6 and 7). Measurements of core temperature by flexible thermistor was considered the
least invasive yet most accurate method. For example tympanic temperature is not as accurate as
measurements taken from the rectum, yet eosophageal measurements would have caused a degree
of discomfort for participants and they would have been unable to consume fluids (Chapter 6 and
7). Gastrointestinal telemetry pills would have been affected by the ingestion of hot fluids (Chapter
6). Skin temperature was recorded at 8 sites using either iButton® technology (Maxim Integrated
Products, Inc., Sunnyvale, CA, USA) (Chapter 4 and 5) or skin thermistors (2020 series, Squirrel
data logger, Grant) (Chapter 6 and 7). Weighted mean skin temperature was calculated using an
area-weighted formula (ISO-standard 9886, 2004) (eq. 1) (Chapters 4, 5, 6 and 7). Metabolic heat
production (M) was assessed and calculated via indirect calorimetry methods (Servomex 1420B,
Crowborough, UK and Harvard Apparatus, Edenbridge, UK) (eq. 2) (Chapters 4, 5, 6 and 7).
Thermal comfort was measured using the McGinnis Scale of Thermal Comfort (Hollies and
Goldman, 1977) (Chapters 4, 5, 6 and 7).
41
3.5 Sample collection and analysis
Saliva and urine samples were collected at least 15 min after fluid consumption and at least 1 h after
the participants had eaten. In addition, saliva samples were obtained after participants had remained
seated for 10 min.
3.5.1 Saliva
Each participant was asked to thoroughly rinse their mouth with water and swallow residual before
saliva collection of un-stimulated whole saliva samples into a pre-weighed universal container (HR
120-EC, A & D instruments, Tokyo, Japan) (Chapters 5 and 7). All saliva samples were collected
for 5 minutes while the participant sat quietly, leant forward and passively drooled with minimal
orofacial movements. Saliva volume was estimated by weighing the universal container
immediately after collection to the nearest mg and saliva density was assumed to be 1.00 g∙ml-1
(Cole and Eastoe, 1988). From this, saliva flow rate was determined by dividing the volume of
saliva by the collection time. Saliva was then aspirated into eppendorfs and stored at -40°C prior to
analysis.
Saliva IgA concentration was determined by ELISA (Salimetrics Europe Ltd, Suffolk, UK) using an
IgA monomer derived from human serum as standard. During the ELISA a constant amount of goat
anti-human s-IgA conjugated to horseradish peroxidase was added to tubes containing specific
dilutions of standards or saliva. The antibody-conjugate was bound to the s-IgA in the standard or
saliva samples. The amount of free antibody remaining was inversely proportional to the amount of
s-IgA present. After incubation and mixing, an equal solution from each tube was added, in
duplicate, to the microtitre plate coated with human s-IgA. The free or unbound antibody conjugate
bound to the s-IgA on the plate. After further incubation, unbound components were washed away.
42
Bound conjugate was measured by the reaction of the peroxidase enzyme on the substrate
tetramethylbenzidine. This reaction produced a blue colour, followed by yellow once the reaction
had been chemically stopped. Optical density was read on a standard plate reader at 450 nm. The
amount of peroxidase was inversely proportional to the amount of s-IgA present in the sample
(Chard, 1990). The intra-assay CV was 1.4% and 2.6% for chapters 5 and 7 respectively. The s-IgA
secretion rate was calculated by multiplying the saliva flow rate by s-IgA concentration.
The alpha amylase ELISA method (Salimetrics Europe Ltd, Suffolk, UK) utilized a chromagenic
substrate, 2-chloro-p-nitrophenol linked with maltotriose (Wallenfels et al. 1978). The enzymatic
action of alpha amylase on this substrate yielded 2-chloro-p-nitrophenol were
spectrophotometrically measured at 405 nm. The amount of alpha amylase activity present in the
sample was directly proportional to the increase in absorbance at 405 nm. For ease of use, the
reaction was read in a 96-well microtiter plate with controls provided. The intra-assay CV was 2.5%
and 2.1% for chapters 5 and 7 respectively.
3.5.2 Urine
First morning urine samples were collected in full and determined for volume, urine specific gravity
(Atago Uricon-NE; NSG Precision Cells, Farmingdale, NY, USA) and osmalality. Urine colour was
determined by a urine colour scale (Armstrong et al. 1994). Provided particpants fulfilled the
hydrated criteria they were able to take part in the studies. Urine was aspirated into eppendorfs,
frozen at -40°C and later thawed for analysis of urinary urea nitrogen content (Chapter 6: Randox
Laboratories, Co. Antrim, UK).
43
3.6 Calculations
Mean skin temperature (Tsk) area-weighted 8-site equation, adjusted for regional proportions (ISO-
standard 9886, 2004):
Mean Tsk = (0.07 · Tforehead) + (0.175 · Tright scapula) + (0.175 · Tleft upper chest)
+ (0.07 · Tright arm in upper location) + (0.07 · Tleft arm in lower location)
+ (0.05 · Tleft hand) + (0.19 · Tright anterior thigh) + (0.2 · Tleft calf ). (eq. 1)
From expired gas samples, values for the respiratory exchange ratio (RER) and VO2 were obtained
and calculated with body surface area (AD) to estimate metabolic heat production (M) in W·m2
using the following equation (Gagge and Gonzalez, 1996):
M = [0.23(RER) + 0.77] · (5.873) (VO2) · (60/ AD) (eq. 2)
3.7 Statistical analysis
Statistical analyses were completed using Statistical Package for Social Sciences (SPSS Version
14). Data were examined using repeated measures ANOVA. Where assumptions of sphericity and
normality were violated appropriate adjustments to the degrees of freedom were made. Effect sizes
(η2) were determined for main outcome measures and were interpreted as small (0.010), medium
(0.060) and large (0.140) (Cohen, 1988). Significance was accepted at P < 0.05. Where significance
occurred Post Hoc Tukey’s HSD was used. All data are presented as Mean ± standard deviation
(SD). Sample sizes were estimated using similar data from previous investigations
(http://www.dssresearch.com/toolkit/sscalc). Alpha and power levels were set at 0.05 and 80%
respectively.
44
CHAPTER FOUR
Thermal Comfort and Thermoregulatory Responses to Cold Exposure in Hypoxia before and
after an Altitude Stay
4.1 Abstract
The purpose of this study was to determine thermal comfort and thermoregulation in relation to
potential cold injury during hypoxic and mild cold exposure before and after an 18-day
mountaineering expedition. In shorts only, ten males completed 2-hour cold air tests (CAT 15°C,
RH 44%) in an environmental chamber in a supine position. Three CATs were performed: 1. Sea
level (SL); 2. Un-acclimatized in normobaric hypoxia (UN: ~4000m); 3. Post expedition in
normobaric hypoxia (PEX: ~4000m). During the CAT core and mean skin temperature were not
different between SL, UN and PEX. However, compared with SL, metabolic heat production was
lower during hypoxic exposures (SL 93 ± 36, UN 68 ± 25, PEX 65 ± 25 W∙m-2
; P < 0.001: mean ±
SD). Observed shivering activity was also lower after the expedition, which suggests a different
contribution of non-shivering and shivering thermogenesis (SL 1.1 ± 0.1, UN 1.0 ± 0.2 and PEX 0.6
± 0.1; P = 0.002). Thermal comfort was increased PEX compared with SL and UN (SL 5.0 ± 1.4,
UN 5.6 ± 1.1, PEX 6.1 ± 0.8; P = 0.004). Following an 18-day mountaineering expedition a lack of
change in core and skin temperature despite a decrease in shivering is consistent with a greater
reliance on non-shivering thermogenesis. The alterations observed post expedition in thermal
comfort suggest a greater thermal tolerance but an increase in susceptibility to cold injury in
hypoxia.
45
4.2 Introduction
High altitude environments may alter perceptual and thermoregulatory responses to the cold that
predispose individuals to greater cold injury (Blatteis and Lutherer, 1976; Cipriano and Goldman,
1975; Golja et al. 2004; Johnston et al. 1996; Savourey et al. 1997). Indeed epidemiological studies
suggest cold injury rates increase at high altitude (Hashmi et al. 1998; Harirchi et al. 2005).
Research studying the effect of hypoxia on thermoregulatory responses to cold is however
equivocal.
Compared with cold alone exposure to cold and hypoxia is associated with a decreased thermal
sensitivity (Golja et al. 2004), lower core temperature and higher skin temperature (Cipriano and
Goldman, 1975; Kottke et al. 1948) which may increase predisposition to cold injury. Nonetheless,
some studies have reported no change in thermal comfort (Golja et al. 2005), core temperature
(Blatteis and Lutherer, 1976; Robinson and Haymes, 1990) or skin temperature (Brown et al. 1952).
An earlier onset of shivering with increased intensity is a common observation in men exposed to
hypoxia and cold (Blatteis and Lutherer, 1976; Bullard, 1961; Robinson and Haymes, 1990). This
may result from reduced non-shivering thermogenesis (NST), demonstrated by a reduced cold-
induced increase in VO2 (Blatteis and Lutherer, 1976). Hypoxic-induced suppression of NST has
been explained by an inhibition of the aerobic catabolism of body fat stores (Robinson and Haymes,
1990). However, patterns of fuel selection during hypoxia in the cold remain to be clarified.
An altered perception of cold sensation has been reported at altitude (Golja et al. 2004) and has
been suggested to be related to a lowered neural activity and delayed signal conduction (Astrup,
1982). A diminished cold sensation is likely to predispose individuals to cold injury because they
neglect basic behavioural thermoregulatory mechanisms (e.g. putting on extra layers and seeking
shelter). However, following acclimation by intermittent exposure to hypoxia, cold and warm
sensitivities of the hand were unchanged compared with baseline measures (Malanda et al. 2008).
46
At present, local and whole body sensations to cold have not been simultaneously measured. In
addition to hypoxic-induced alterations in cold sensation, anecdotal reports suggest hypoxia also
alters thermal comfort. Early reports describe the pain to single limb cold water immersion
(Mathew et al. 1979) and thermal discomfort to whole body mild cold air exposure (Blatteis and
Lutherer, 1976) to be greater at altitude than at sea level. These same anecdotal reports suggest that
the increased pain and discomfort did not abate with altitude acclimatisation (Mathew et al. 1979;
Blatteis and Lutherer, 1976). Greater pain to single limb cold water immersion has recently been
confirmed by a more systematic investigation (Daanen and van Ruiten, 2000). However, the effect
of whole body cold exposure during acute hypoxia and following a high altitude stay on perception
of thermal comfort has yet to be explored.
Demonstrated by the maintenance of a higher mean body temperature and mean skin temperature
during acute cold stress, hypoxic acclimatisation has been shown to induce greater cold tolerance
(Blatties and Lutherer, 1976; Mathew et al. 1979). Studies also suggest altitude acclimatisation may
result in NST recovery (Blatteis and Lutherer, 1976; Mathew et al. 1979). The amount of recovery
however remains unclear and is complicated by the methods of data collection used (Blatteis and
Lutherer, 1976; Cipriano and Goldman, 1975; Mathew et al, 1979). For example, sample sizes in
these studies were small and methods to determine shivering activity were not valid. It is plausible
to suggest that while un-acclimatised exposure to hypoxia may inhibit the catabolism of fat stores
and thus reduce NST, the same might not be true following acclimatisation. Research has examined
thermoregulatory responses after acclimatisation during cold exposure at sea level (Blatteis and
Lutherer, 1976; Savourey et al. 1997), yet no studies have assessed such responses during hypoxia
in the cold following a mountaineering expedition.
The effect of hypoxia in the cold on thermoregulatory mechanisms of un-acclimatised men is
equivocal. It is unknown whether acclimatisation, resulting from mountaineering activity at altitude,
affects thermoregulatory, metabolic and perceptual responses to hypoxia in the cold. The aim of the
47
present study therefore, was to examine these responses in un-acclimatised and acclimatised
individuals after an 18-day Alpine expedition. It was hypothesised that un-acclimatised exposure to
hypoxia and cold would impair thermoregulatory responses compared to those reported in
normoxia. Secondly, it was hypothesised that acclimatisation due to the expedition would restore
the responses toward those observed in normoxic cold exposure.
48
4.3 Method
4.3.1 Participants
Ten healthy males (mean ± SD: age, 21.7 ± 2.4 years; height, 181.7 ± 5.1 cm; body mass, 76.4 ± 9.9
kg and body fat, 11.6 ± 6.6 %), accustomed to multi-day expedition-type activities were recruited
from an 18-day Alpine expedition (Figure 4.1). Participants gave written consent and medical
history before the study that had received local Ethics Committee approval.
4.3.2 Study design
Participants completed three experimental trials in a normobaric, temperature and humidity
controlled chamber (Dry bulb temperature of the chamber remained at 15°C with a relative
humidity (RH) 40% and 0.2 m.s-1
wind velocity; Delta Environmental Systems, Chester, UK) over
a 12 week period. Trials were 1. sea-level (SL: FIO2 = 0.209); 2. Un-acclimatised in normobaric
hypoxia (UN: FIO2 = 0.125, ~4000m); and 3. post expedition acclimatised in normobaric hypoxia
(PEX: FIO2 = 0.125, ~4000m). To avoid an order effect SL and UN were performed before the
expedition in half of the participants and 2 months after the expedition in the remainder. During
PEX the mean altitude gained on a daily basis was 2989 ± 867 m.
4.3.3 Experimental procedures
Having consumed no food within 4 hours, participants arrived to the laboratory euhydrated
(Chapter 3). After voiding bladder and bowels, anthropometric measures of height and body mass
were obtained. Body composition was analysed by segmental multiple-frequency bioelectrical
impedance (InBody 230, Biospace, Seoul, S Korea: Malavolti et al. 2003; Jensky-Squires et al.
2008). Daily energy requirements were determined by body composition and a mean of daily
49
metabolic rate, hourly basal metabolic rate, eight hours sleep, eight hours of occupational activities
(e.g. moving, sitting and standing) and eight hours of residual time (WHO, 2004).
4.3.4 Experimental Trials
Participants completed each trial at the same time of day. Following pre-trial measures, participants
began a 10 minute supine rest in a thermo-neutral environment (ambient temperature: 21.3 ± 1.1°C;
RH: 52 ± 5.4%). Resting values of core (Trec) and skin (Tsk) temperature were recorded. Metabolic
heat production (M), thermal comfort, peripheral and central coldness (Borg CR100) (Borg and
Borg, 2001), heart rate (HR) (Polar, Electro Kempele, Finland), and arterial oxygen saturation
(SaO2%) by finger pulse oximetry (Supermon 7210, Kontron, Watford, UK), were also recorded.
Following baseline measures and wearing shorts only, participants entered the chamber and rested
supine upon roll mats situated on the floor for 150 minutes. Core temperature, M, SaO2%, HR,
whole body thermal comfort and peripheral and central coldness were recorded every 5 minutes.
Skin temperature was recorded every minute. To detect potential CIVD, toenail and fingernail bed
temperatures were measured with i-buttons taped to the large toe and index finger of the right hand
and foot. During the initial 30 minutes, participants were covered with a standard duvet (4.5 togs).
This thermo-neutral condition (van Ooijen et al. 2005) ended and the 120 minute CAT began when
the duvet was removed. Thermo-neutral conditions were necessary in order to establish any change
between non-shivering thermogenesis and shivering thermogenesis.
Electromyograms (AD instruments Powerlab) of the pectoralis major determined shivering activity.
Pilot work demonstrated this muscle to provide accurate traces with little background noise
compared to abdominal or quadriceps muscles. In addition, acetate traces were taken of each
participant’s torso to ensure exact placement of EMG leads during each trial. EMG data was logged
every minute and measured in micro-volts. Shivering was also rated using a 4 point scale by an
50
observer (Appendix F) (Blatteis and Lutherer, 1976). Training was given to a maximum of two
researchers in order to maintain consistant observational practice. Participants remained in the
environmental chamber for 150 minutes unless: 1. Trec decreased to 36°C or fell 1.5°C below
resting, 2. Lake Louise scores went above 1 to highlight the presence of headache (hypoxic trials
only) or 3. participants chose to withdraw. Upon completion participants were re-warmed and
monitored until core temperature was within 0.5°C of resting.
Figure 4.1. Mean daily altitude of participants during an Alpine expedition.
4.3.5 Statistical analyses
A sample size of nine was estimated using rectal temperature data from a previous investigation
(Blatteis and Lutherer, 1976). To allow for incompletion, ten subjects were recruited. A one-way
fully repeated-measures ANOVA was performed on body mass and composition data and urine
osmolality. Two-way fully repeated-measures ANOVA (time x trial) were performed on
thermoregulatory, metabolic and EMG data. Data was normally distributed.
Day
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
51
4.4 Results
4.4.1 Environmental chamber conditions, hydration status, body mass and composition
Chamber temperature (SL: 15.0 ± 0.1; UN: 15.2 ± 0.2; PEX: 15.2 ± 0.2°C, F2, 10 = 1.168, P = 0.350)
and relative humidity (SL: 46 ± 4; UN: 43 ± 8; PEX: 39 ± 4%, F2, 10 = 0.292, P = 0.753) were not
different between trials. Urine osmolality indicated hydration status was similar before each trial
(SL: 364 ± 129, UN: 366 ± 129, PEX: 382 ± 202 mOsm∙Kg-1
, P = 0.670). Body fat and mass were
unchanged before and after the expedition (SL: 11.6 ± 6.6; PEX: 11.5 ± 6.3 %, P = 0.745; SL: 75 ±
10; PEX: 76 ± 10 Kg, P = 0.786 respectively).
4.4.2 Core and skin temperature responses
Cold exposure caused Trec to decline similarly during all CATs (F12, 108 = 4.456, P = 0.000, η2
=
0.326) (Figure 4.2). Cold exposure reduced mean Tsk in all trials (F12, 108 = 170.084, P = 0.000, η2
=
0.942) but was also not influenced by hypoxia (F2, 18 = 1.450, P = 0.261, η2
= 0.136) (Figure 4.3).
Skin temperature at the forehead was lower throughout SL compared to UN and PEX (F2, 18 =
9.875, P = 0.001, η2 = 0.521) (Table 4.1). Skin temperature at the left chest was also lower during
SL compared to PEX following 10 minutes of cold exposure (F1.291, 11.618 = 4.743, P = 0.043, η2 =
0.324). No differences occurred for any other individual skin sites (Table 4.1).
Temperatures at the fingernail bed were the same in each trial (F2, 18 = 0.033, P = 0.967, η2
= 0.004)
(Table 4.2). During the initial exposure, temperatures at the toenail bed were also the same (F2, 18 =
1.324, P = 0.291, η2
= 0.101). However, following 60 minutes, toenail bed temperature was lower
during UN compared to SL (F2, 18 = 3.793, P = 0.042, η2
= 0.288) (Table 4.2). An interaction
established cold exposure evoked a cooler toenail bed temperature in unacclimsatised individuals
(F24, 216 = 6.882, P = 0.000, η2
= 0.356).
52
Figure 4.2. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on Trec (°C). Values are mean ±
SD. * significant difference vs. 0 mins (P < 0.05).
Figure 4.3. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on mean skin temperature (°C).
Values are mean ± SD. * significant difference vs. 0 mins (P < 0.05).
27
28
29
30
31
32
33
34
0 10 20 30 40 50 60 70 80 90 100 110 120
Skin
Te
mp
era
ture
(°C
)
Time (mins)
36
36.2
36.4
36.6
36.8
37
37.2
37.4
37.6
37.8
38
0 10 20 30 40 50 60 70 80 90 100 110 120
Co
re T
em
pe
ratu
re (
°C)
Time (mins)
53
Table 4.1. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level (SL) and at 4000 m before (UN) and after (PEX) acclimatisation on skin temperature (°C).
Values are mean ± SD. * significant difference vs. 0, † significant difference vs. SL (P < 0.05).
Skin temperature at individual sites (°C)
SL UN PEX
Forehead
0 30.3 32.0† 32.4†
60 28.7* 30.4*† 31.0*†
120 28.6* 30.3*† 30.8*†
Mean (SD) 28.9 ± 2.3 30.7 ± 2.0 31.1 ± 1.1
Right Scapula
0 34.0 34.7 34.0
60 34.5 35.1 34.7
120 34.4 34.4 34.1
Mean (SD) 34.5 ± 2.2 35.1 ± 0.7 34.4 ± 1.0
Left chest
0 32.9 32.6 32.8
60 27.2* 28.2* 29.1*
120 27.5* 28.4* 29.5*
Mean (SD) 27.9 ± 2.8 28.7 ± 3.1 29.7 ± 1.8†
Right upper arm
0 32.7 33.5 32.6
60 27.7* 29.0* 28.5*
120 27.2* 28.1* 27.4*
Mean (SD) 28.4 ± 2.0 29.6 ± 1.9 29.0 ± 1.7
Forearm
0 32.1 32.5 32.5
60 27.3* 27.6* 28.2*
120 26.2* 26.1* 26.9*
Mean (SD) 27.9 ± 2.3 28.1 ± 2.1 28.7 ± 2.0
Left hand
0 27.0 28.0 28.3
60 22.2* 22.6* 23.7*
120 21.3* 20.8* 22.6*
Mean (SD) 22.8 ± 3.2 22.9 ± 2.4 24.2 ± 3.3
Right thigh
0 32.3 33.2 33.0
60 29.9* 30.3* 30.3*
120 29.2* 29.9* 29.8*
Mean (SD) 30.1 ± 1.9 30.6 ± 1.7 30.6 ± 1.9
Left calf
0 32.1 31.9 32.1
60 31.9 30.3* 30.9*
120 30.9* 29.7* 29.8*
Mean (SD) 31.9 ± 1.2 30.6 ± 2.2 31.0 ± 1.9
54
Table 4.2. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level (SL) and at 4000 m before (UN) and after (PEX) acclimatisation on fingernail and toenail
temperature (°C).
Values are mean ± SD. * significant difference vs. 0, † significant difference vs. SL (P < 0.05).
4.4.3 Metabolic responses
Metabolic heat production was similar at rest in all trials during exposure to a thermo-neutral,
normoxic environment (F2, 18 = 0.038, P = 0.963, η2 = 0.004). As expected, M increased in all trials
during the CAT (F12, 108 = 12.071, P = 0.000, η2
= 0.528). However, compared to SL, M was less
after 20 minutes of CAT on UN and PEX (F2, 18 = 7.907, P = 0.003, η2
= 0.431) (Figure 4.4).
During UN, RER was higher than SL and PEX (F2, 18 = 6.501, P = 0.008, η2
= 0.327) (Table 4.3).
This may have been a direct result of the hypoxic ventilatory response during UN, however the
same RER reponse was not observed during PEX yet a similar pattern in ventilator response was.
During CAT, the percentage of kilocalories derived from carbohydrate oxidation, calculated using
RER values, was greater during UN compared to SL and PEX (F2, 18 = 9.025, P = 0.002, η2
= 0.416)
(Figure 4.5).
Fingernail Toenail
SL UN PEX SL UN PEX
0 23.2 ± 3.3 24.2 ± 3.4 24.3 ± 3.8 20.6 ± 1.2 21.0 ± 1.2 21.9 ± 1.0
60
20.3 ± 3.7* 20.3 ± 3.7* 20.7 ± 3.4*
17.8 ± 0.6* 17.5 ± 0.9*† 18.2 ± 1.4*
120 18.3 ± 1.4* 17.5 ± 1.1 * 18.2 ± 1.6* 16.9 ± 1.1* 15.2 ± 1.0*† 16.0 ± 0.8*
Mean (SD) 20.4 ± 3.5 20.5 ± 3.9 20.6 ± 3.6 18.1 ± 0.9 17.7 ± 0.9† 18.2 ± 0.9
55
Figure 4.4. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on metabolic heat production
(W∙m-2
). Values are mean ± SD. * significant difference vs 0 mins, † significant difference vs. SL
(P < 0.05).
Table 4.3. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level (SL) and at 4000 m before (UN) and after (PEX) acclimatisation on the respiratory exchange
ratio (RER).
RER (respiratory exchange ratio)
SL UN PEX
0 0.84± 0.14 0.76 ± 0.05 0.74 ± 0.03
60 0.91 ± 0.3 1.04 ± 0.13*# 0.87 ± 0.13
120 0.81 ± 0.11 1.05 ± 0.14*†# 0.85 ± 0.09
Mean 0.9 ± 0.2 1.00 ± 0.1 0.9 ± 0.1
Values are mean ± SD. * significant difference vs.0 mins, † significant difference vs. SL, #
significant difference vs. PEX (P < 0.05).
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60 70 80 90 100 110 120
Me
tab
olic
He
at P
rod
uct
ion
(W
·m2)
Time (mins)
♦; *
■, △; *
†
56
Figure 4.5. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ■ ) and at 4000 m before ( ■ ) and after ( ■ ) acclimatisation on carbohydrate and lipid
oxidation (%).Values are mean ± SD. † significant difference vs. SL, # significant difference vs.
PEX (P < 0.05).
4.4.4 Observed shivering activity and EMG
After 80 minutes, observed shivering activity was lower PEX compared to SL and UN (F2, 18 =
6.322, P = 0.008, η2
= 0.322) (Figure 4.6). After 110 minutes, maximum observed shivering
activity was reached in all trials. However, shivering intensity at this time was higher during SL and
UN (2 = Generalised but discontinuous shivering) compared to PEX (1 = Mild shivering bursts).
While not significant, EMG traces displayed lower shivering activity during PEX compared to SL
and UN, particularly toward the end (F2, 18 = 0.908, P = 0.421, η2
= 0.087) (Figure 4.7).
0
20
40
60
80
100
120
Carboyhdrate Oxidation (%) Lipid oxidation (%)
Pe
rce
nta
ge k
Cal
de
rive
d f
rom
car
bo
hyd
rate
an
d
lipid
(%
)
Tneut †#
†#
Carbohydrate Oxidation (%) Lipid Oxidation (%)
57
Figure 4.6. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ■ ) and at 4000 m before (■ ) and after (■ ) acclimatisation on observed shivering activity.
Values are mean ± SD. * significant difference vs. 0 mins, † significant difference vs. SL, ¥
significant difference vs. UN (P < 0.05).
Figure 4.7. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on EMG activity of the
pectoralis major (µV). Values are mean ± SD.
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50 60 70 80 90 100 110 120
Ob
serv
ed
Sh
ive
rin
g In
ten
sity
(0
: N
o S
hiv
eri
ng
- 3
: M
arke
d a
nd
Co
nti
nu
ou
s)
Time (mins)
■; †, ¥ *
Tneut
-200
0
200
400
600
800
1000
1200
1400
1600
0 10 20 30 40 50 60 70 80 90 100 110 120
Shiv
eri
ng
acti
vity
(µ
V)
Time (mins)
58
4.4.5 Thermal comfort and pain sensation
Thermal comfort was increased PEX compared with SL and UN (F1.284, 11.558 = 11.779, P = 0.004,
η2
= 0.542) (Figure 4.8). Perceived peripheral coldness was lower during PEX compared to SL and
UN (F2, 18 = 14.407, P = 0.000, η2
= 0.572) (Figure 4.9A). An interaction established that perceived
peripheral coldness depended on hypoxic acclimatisation (F24, 216 = 3.441, P = 0.000, η2
= 0.086).
Perceived central coldness was also lower during PEX compared to SL and UN (F2, 18 = 5.678, P =
0.012, η2
= 0.365) (Figure 4.9B). Similarly, an interaction suggested perceived central coldness was
also dependant on hypoxic acclimatisation (F24, 216 = 2.018, P = 0.005, η2
= 0.084). Perceived
coldness at the periphery was higher than perceived central coldness throughout all trials (P < 0.05).
Figure 4.8. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on thermal comfort (McGinnis’
thermal comfort scale). Values are mean ± SD. * significant difference vs. 0 mins, † significant
difference vs. SL (P < 0.05).
0
1
2
3
4
5
6
7
8
0 10 20 30 40 50 60 70 80 90 100 110 120
The
rmal
Co
mfo
rt (
1:
So c
old
I am
he
lple
ss –
8:W
arm
b
ut
fair
ly c
om
fort
able
)
Time (mins)
△; †
59
Figure 4.9. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ) and at 4000 m before ( ■ ) and after ( △ ) acclimatisation on perceived central coldness
(A) and Perceived peripheral coldness (B). Values are mean ± SD. * significant difference vs. 0
mins; † significant difference vs. SL, ¥ significant difference vs. UN (P < 0.05).
4.4.6 Heart rate and Arterial oxygen saturation
HR was higher UN compared to PEX during the initial 50 minutes (F2, 18 = 7.254, P = 0.005, η2
=
0.385) (Table 4.4). Arterial oxygen saturation was lower during UN compared to SL (F1.082, 9.734 =
23.517, P = 0.001, η2
= 0.694) (Table 4.4). Arterial oxygen saturation during PEX was not different
to SL or UN.
Tneut
-10
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70 80 90 100 110 120
Ce
ntr
al C
old
ne
ss (
0:
No
thin
g at
all-
50
: St
ron
g /
He
avy)
Time (mins)
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70 80 90 100 110 120
Pe
rip
he
ral C
old
ne
ss (
0:
No
thin
g at
all
- 5
0:
Stro
ng
/ H
eav
y)
Time (mins)
A. B.
#*†
A. Tneut
Time (mins)
Shiv
erin
g A
ctiv
ity
*†
*† *† *†
*† *†
*
△; †, ¥ *
△; ¥
△; †
60
Table 4.4. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level SL) and at 4000 m before (UN) and after (PEX) acclimatisation on heart rate (beats∙min-1
) and
arterial oxygen saturation (SaO2 %).
HR (beats∙min-1
) SaO2(%)
SL UN PEX
SL UN PEX
0 55 ± 9 60 ± 9# 54 ± 6
98 ± 2 85 ± 9# 89 ± 3
60 57 ± 11 56 ± 10 54 ± 9
97 ± 2 85 ± 7† 90 ± 4
120 59 ± 10 65 ± 10 59 ± 9
97 ± 2.6 86 ± 6† 90 ± 4
Mean 57 ± 11 60 ± 10 54 ± 9
97 ± 3 85 ± 9 91 ± 5
Values are mean ± SD. † significant difference vs. SL, # significant difference vs. PEX (P < 0.05).
4.4.7 Results summary
The key findings of these results demonstrate an unaltered core and mean skin temperature during
UN and PEX, compared with SL. However, metabolic heat production was significantly altered
during UN and remained so PEX. RER and substrate oxidation were altered during UN as was
shivering activity, which demonstrated a reduced capacity for non-shivering thermogenesis.
Thermal comfort was increased PEX compared with SL and UN. Heart rate was higher UN
compared with PEX during the initial 50 minutes. Arterial oxygen saturation was lower during UN
compared with SL.
61
4.5 Discussion
The aim of this study was to examine the acute and chronic effects of hypoxia upon
thermoregulation in mild cold. As anticipated, un-acclimatised men exposed to hypoxia in the cold
demonstrated an impaired thermoregulatory and metabolic response compared with cold exposure
at sea level. This was demonstrated by a reduced contribution of NST via an increased catabolism
of CHO that initiated an earlier onset and increased intensity of shivering activity. Despite this, cold
exposure in hypoxia regardless of acclimatisation did not impair core or mean skin temperature
compared to cold alone. Following prolonged hypoxic exposure however, perceptions of thermal
comfort reflected an improved cold tolerance and impaired thermal sensitivity that might lead to
poor behavioural thermoregulation and greater risk of cold injury.
Contradictory to early reports (Bullard, 1961; Cipriano and Goldman, 1975; Kottke et al. 1948), un-
acclimatised exposure to hypoxia in the cold did not increase the rate of heat loss from the core or
periphery. Core temperature however, has been reported elsewhere as unaltered during both
normobaric and hypobaric hypoxia in the cold (Blatteis and Lutherer, 1976; Brown et al. 1952;
Robinson and Haymes, 1990). On the contrary, when individuals were un-acclimatised, reduced
temperatures at the toenail bed were observed. Exposure to acute hypoxia in the cold has been
associated with a reduction in CIVD at the extremities (Mathew et al. 1977; Takeoka et al. 1993)
and an increased risk of local cold injury at altitude (Golja et al. 2004). Following the 18-day
mountaineering expedition at altitude, core and mean skin temperatures during subsequent cold
exposure in hypoxia were also unaltered compared with cold alone. Local temperature at the
forehead and left chest however, were higher during acclimatised exposure to hypoxia compared to
normoxia. Future studies should look to measure skin blood flow at these local areas to see if
warming is repeated. Potentially, warmer skin temperature at these sites is reflecting an adaptation
to hypoxia following a prolonged stay.
62
Thermal comfort and perception provides the basis for the initiation of behavioural
thermoregulation (Golja et al. 2004). During unacclimatised hypoxic-cold exposure in the present
study, men rated their thermal comfort the same as in cold alone. This has been previously reported
(Golja et al. 2005). Core and skin temperature sensors transform thermal energy into neural coded
information that give a sensation of either cold or warmth and a perception of pleasure or
displeasure (Cabanic, 1969, 1981; Hensel 1976). Given that core and mean skin temperatures were
the same in both trials it is likely the amount of thermal energy was also the same which suggests
why no differences in thermal comfort occurred. This contradicts previous work where an inspired
air content of 10% oxygen decreased cold sensation in humans (Golja et al. 2004). However, since
it has been suggested oxygen limitations may only begin to implement thermoregulatory
impairments when inspired oxygen is less than 11% (Gautier et al. 1997), the modest level of
hypoxia that participants were exposed to in the present study may have induced milder
impairments. It should be noted however, that arterial oxygen saturation levels varied substantially
between participants during unacclimatised hypoxic exposure and conclusions from this study
therefore should be generalised to wider populations with caution. Nonetheless, despite variations
no participant rated themselves to be suffering AMS symptoms as highlighted by the Lake Louise
scale.
Post-expedition, a decrease in cold sensation at the core and periphery was demonstrated. This
suggests prolonged exposure to altitude stressors during mountaineering may affect core and skin
temperature sensors so that neural coded information is impeded and nerve conduction impaired
(Golja et al. 2004; Malanda et al. 2008). When oxygen supply diminishes below the metabolic
demands of the nerve tissue, the energy requiring cell functions are reduced and membrane
depolarisation causes complete loss of neural cell function (Astrup, 1982; Golja et al. 2004). Neural
impairment by prolonged hypoxic exposure may affect both the central and peripheral nervous
system. Acclimatised individuals at altitude may often feel warmer than their core temperature
63
would suggest. As a result, behavioural thermoregulation may be neglected and as altitude
continues to increase and ambient temperatures reduce, impaired thermal sensation may increase
the likelihood of cold injury (e.g. hypothermia and frostbite).
Metabolic heat production was reduced during the initial hypoxia and cold exposure, which was
similar to earlier reports (Blatteis and Lutherer, 1976; Robinson and Haymes, 1990). A reduction in
heat production coupled with an earlier onset and more intense shivering activity supports that
hypoxia may suppress NST (Blatteis and Lutherer, 1976; Bullard, 1961; Gautier, 1996; Robinson
and Haymes, 1990). Given that BAT is the primary energy source for NST and has been observed
to be mainly activated during cold exposure (van Marken Lichtenbelt et al. 2009), suggests that
hypoxia may indeed restrict the activity of BAT in the cold leading to an increased likelihood of a
reduction in body temperature. This is supported by previous work which suggests the hypoxic-
induced suppression of NST by an inhibition of the aerobic catabolism of lipid stores, when un-
acclimatised, may occur through an increased hormonal response to hypoxic stress that decreases
the lipolytic response of adipocytes and thus lowers lipid mobilisation (de Glisezinski et al. 1999;
Masoro, 1966; Robinson and Haymes, 1990).
Carbohydrate oxidation increased by almost 100% when un-acclimatised men were exposed to
hypoxia and cold compared with cold alone. However, this increase was reduced by 50% post-
expedition. Increased carbohydrate oxidation occurs to fuel intense shivering thermogenesis
(Martineau and Jacobs, 1988) which may explain how the body successfully maintained core and
mean skin temperature given the reduction of NST. Increased shivering activity coupled with an
increased rate of carbohydrate oxidation suggests a physiological response similar to moderate
exercise (Roberts et al. 1996a). While muscle glycogen and blood glucose contribute equally to
carbohydrate energy production, sources become depleted quickly compared to fatty acids and
glycerol (Coyle, 1995). Therefore, un-acclimatised men with a diminished ability to oxidise lipids
in hypoxic and cold environments risk muscle glycogen depletion, earlier onset of fatigue and
64
ultimately cold injury. Comparable with un-acclimatised exposure to cold and hypoxia, the
metabolic response remained suppressed post-expedition. Nonetheless, shivering activity was
reduced and was also less than normoxia. This finding supports that NST recovery may occur
following a stay at altitude which may result from a small recovery in fuel selection.
Present results also suggest there may be an increase in thermal comfort following a stay at high
altitude. Reduced cold sensitivity and increased thermal comfort accompanying acclimatisation may
be related to the observed reductions in shivering activity post-expedition. Given peripheral thermo-
receptors at the skin control the onset of shivering it would appear these are not readily stimulated
upon exposure to mild cold in acclimatised individuals. In conclusion, following an 18 day
mountaineering expedition, a decrease in shivering despite no changes in core or mean skin
temperature is consistent with a greater reliance on NST. The alterations observed post-expedition
in thermal comfort may suggest a greater thermal tolerance and poorer thermal sensation that may
increase susceptibility to cold injury.
65
CHAPTER FIVE
Hypoxia and cold effects on Mucosal Immunity before and after an altitude stay
5.1 Abstract
The purpose of this study was to examine the effect of hypoxia and cold on mucosal immunity. Ten
males completed four different trials. Three 2 hour CATs were performed in an environmental
chamber (CAT 15°C, RH 44%): 1. sea-level (n = 15) (SL: FIO2 = 0.209); 2. un-acclimatized in
normobaric hypoxia (n = 15) (UN: FIO2 = 0.125, ~4000m) and 3. post expedition in normobaric
hypoxia (n = 10) (PEX: FIO2 = 0.125, ~4000m). Participants also completed a thermo-neutral
control trial (n = 10) (TC: FIO2 = 0.209, 19.5°C and 45% RH). Un-stimulated whole saliva samples
were collected before, at the end of CAT, immediately after, and one-hour after the CAT. On TC,
saliva was collected at the same time of day as CAT trials. Cold exposure caused a progressive
decline in Trec (~0.4°C) throughout all trials (P = 0.001) which was not further altered by altitude (P
= 0.097). Hypoxia also caused a significant reduction in oxygen saturation during UN (SL: 98 ± 2,
UN: 86 ± 6 PEX: 91 ± 5 %; P = 0.000). Saliva flow rate (µl·min-1
) was decreased by hypoxia in the
cold during UN compared with SL and TC (P = 0.047; P = 0.022) respectively. No differences were
observed in s-IgA concentration (µg·ml-1
) (P = 0.642) or s-IgA secretion rate (µg·min-1
) (P =
0.335). Cold exposure however, increased α-amylase concentration compared with TC (P = 0.003).
In combination, a cold-induced increase in α-amylase concentration and a hypoxic-induced
reduction in saliva flow rate might increase the risk of infection for un-acclimatised individuals at
altitude since saliva is important for oral washing.
66
5.2 Introduction
Given unacclimatised exposure to cold and hypoxia denotes changes in thermoregulatory
homeostasis (Chapter 4), it would be beneficial to understand how these correspond to immune
function in the same conditions. This knowledge could better inform individuals regarding health
risks involved when traveling to cold, hypoxic environments. A study investigating
thermoregulation and immune function using controlled methodology has not been reported.
Sympathoadrenal responses associated with acute and chronic high altitude exposure can influence
immune function which may increase the risk of illness and infection while individuals are a far
distance from appropriate medical resources (Meehan et al. 1988; Mazzeo et al. 1994; Mazzeo et al.
1995; Mazzeo et al. 2001). For example, early research has found a higher prevalence of pneumonia
among military troops stationed at high altitude (Singh et al. 1977). However, findings have limited
application to new and un-acclimatised arrivals at altitude. Furthermore, individuals visiting high
altitudes are often exposed to multiple stressors, including cold, dehydration, novel infectious
agents and poor hygiene. It is incorrect to assume an increase in infection is exclusively due to
hypoxia-induced immune suppression. Whether the risk of illness or infection is exacerbated in un-
acclimatised expeditioners upon arrival to hypoxic and cold environments remains unknown.
Furthermore, it has not been clarified whether such potential detriments to mucosal immunity are
reduced following a period of altitude acclimatisation. Given the possibility of low oxygen
conditions during space flight, this information may also have significant implications for
spaceflight personnel during long term missions (Cogoli, 1981; Taylor and Dardano, 1983).
Cold exposure is associated with an increased incidence of bronchorrhea, sinusitis, and upper
respiratory tract infections (URTI) (Clothier, 1974; Giesbrecht, 1995; Castellani et al. 2002; Lavoy
et al. 2011). Much research to date however, has examined individuals undertaking the additional
stress of physical activity which likely exacerbates the immune response to cold (Castellani et al.
2002). Since URTIs are the main cause of illness and missed practise in elite cross country skiers
67
(Berglund and Hemmingson, 1990), cold-induced decrements in immune-surveillance may be a
problem for individuals at altitude. The additional stressor of cold in hypoxia-exposed humans may
evoke a similar suppression on the mucosal immune system as that demonstrated with physical
activity in the cold.
Short term hypoxia is reported to induce similar immunosuppression upon the mobilisation of T-
cells and natural killer cells (Klokker et al. 1993; Klokker et al. 1995) as that demonstrated during
surgery (Lennard et al. 1985) and exercise (Pedersen et al. 1990). The regulation of cytokine
production and release has also been shown to be reduced in hypoxia (Pedersen and Steensberg,
2002). On the contrary, nasal mucosal immunity is suggested to be unchanged by hypoxia and any
reduced secretory IgA and lysozyme levels may be caused by the combined stresses of cold,
isolation and reduced humidity (Meehan et al. 1988; Muchmore et al. 1981). While cold exposure is
often unavoidable at high altitude, the effect of hypoxia itself upon the normal mucosal immune
response to cold has received little attention. Salivary IgA is often the mucosal secretion of choice
for studies of the human mucosal immune system due to the ease and standardisation of collections.
It is well established to characterise the effects of many stressors, for this reason however, it may
not always reflect compencies in other aspects of immune defence and therefore it is of benefit to
assess additional mucosal immune parameters. Secretion of amylase from saliva glands is
controlled by autonomic nervous signals and substantial literature reveals that salivary amylase is
correlated to sympathetic activity under conditions of stress. Specifically, α-amylase increased
under a variety of physically (i.e. exposure to heat or cold) and psychologically (exams) stressful
condtions (Chatterton et al. 1996). Furthermore, s-IgA acts with α-amylase to provide the first line
of defence against pathogens and antigens at the mucosa. A study to determine the effect of acute
and chronic hypoxia on s-IgA and α-amylase responses in the cold compared to cold alone will
likely clarify any increased risk of infection upon and following ascent to high altitude.
68
The aim of the present study was to examine the effect of hypoxia on saliva responses to the cold
before and after an 18 day altitude expedition. This was achieved by comparing saliva responses in
thermo-neutral, mild cold, and mild cold with hypoxia. To determine the effect of prolonged
exposure to a multi-stressor, mountainous environment, typically experienced by mountaineers, the
same saliva responses were compared in the same mild cold with hypoxia. Given fluctuations in
catecholamines and cortisol activate the SNS and effect s-IgA and amylase responses; it was
unnecessary to measure these stress hormones if changes in mucosal immunity occurred. It was
hypothesised that un-acclimatised exposure to hypoxia would evoke greater detrimental effects on
mucosal immunity in the cold compared with normoxia. This might include an increase in α-
amylase concentration and a reduction in s-IgA secretion rate. Following an altitude stay it was
hypothesised that typical s-IgA and α-amylase responses to the cold would be resumed regardless of
hypoxia.
69
5.3 Method
5.3.1 Participants
Fifteen healthy males (mean ± SD: age, 22 ± 3 years; height, 180 ± 6 cm; body mass, 66 ± 12 kg
and body fat, 12 ± 6 %) were recruited from an Alpine expedition. Due to unexpected
circumstances only ten participants were able to complete PEX and TC. Participants gave written
consent and medical history before the study which received local Ethics Committee approval.
5.3.2 Preliminary measurements
Before each experimental trial participants arrived at the laboratory after an overnight fast having
consumed no food, caffeine or alcohol within 10 h. Participants ingested water equal to at least 35
ml·kg-1
body mass the day prior to each trial. After voiding bladder and bowels, nude body mass
and height were measured. Daily energy requirements were determined by body composition and
calculated from a mean of daily metabolic rate, hourly basal metabolic rate, eight hours of sleeping,
eight hours of occupational activities (e.g. moving, sitting and standing) and eight hours of residual
time (WHO, 2004). Energy requirements were provided and given as standardised meals (breakfast,
lunch and dinner) in the 24 h period prior to each experimental trial.
5.3.3 Experimental Trials
Participants completed three experimental trials in a normobaric, temperature and humidity
controlled chamber (Dry bulb temperature of the chamber remained at 15°C with a relative
humidity (RH) 40% and 0.2 m.s-1
wind velocity; Delta Environmental Systems, Chester, UK) over
a 12 week period (Chapter 4). Trials were 1. sea-level (SL: FIO2 = 0.209); 2. un-acclimatised in
normobaric hypoxia (UN: FIO2 = 0.125, ~4000m); and 3. post-expedition (n=10) in normobaric
hypoxia (PEX: FIO2 = 0.125, ~4000m). To avoid an order effect SL and UN were performed before
70
the expedition in half of the participants and 2 months after the expedition in the remainder. Ten of
the fifteen participants also completed a thermo-neutral control trial (TC) fully clothed in ambient
conditions (19.5°C and 45% RH) to account for the diurnal variation in saliva responses.
Participants completed each trial at the same time of day and consumed no food, caffeine or alcohol
within 4 h of each trial. Throughout UN and PEX, inspired oxygen fraction (FIO2) was equal to
0.125 to simulate an altitude of approximately 4000 m. Following pre-trial measures and after 10
minutes supine rest in normothermia (ambient temperature: 21.3 ± 1.1°C; relative humidity: 52 ±
5.4%), baseline measures of Trec and SaO2% were recorded. Wearing shorts only, participants then
entered the chamber and rested in a supine position on roll mats situated upon the floor for 120
minutes. Early removal from the chamber occurred if: 1. core temperature reduced to 36°C or fell
1.5°C below baseline, 2. Lake Louise scores went above 1 (UN and PEX only) or 3. participants
chose to withdraw. Upon completion participants were re-warmed and monitored until core
temperature was within 0.5°C of baseline.
5.3.4 Saliva collection and analysis
Un-stimulated whole saliva samples were collected using pre-weighed universal tubes (Chapter 3).
Saliva samples were collected while the participant sat quietly in the laboratory (1: before CAT, 2:
at the end of CAT – inside chamber conditions, 3: immediately after CAT – outside chamber (21.3
± 1.1°C and rh: 52 ± 5.4%), 4: one-hour after CAT (21.3 ± 1.1°C and rh: 52 ± 5.4%). Saliva volume
was estimated by weighing the universal container immediately after collection to the nearest mg.
From this, saliva flow rate was determined by dividing the volume of saliva by the collection time.
Saliva was aspirated into Eppendorfs and stored at -40°C for further analysis. After thawing s-IgA
concentration was determined by ELISA (Salimetrics Europe Ltd, Suffolk, UK) using IgA
71
monomer from human serum as standard. The intra-assay CV was 1.4%. s-IgA secretion rate was
calculated by multiplying the saliva flow rate by s-IgA concentration.
Alpha amylase concentration was determined by ELISA (Salimetrics Europe Ltd, Suffolk, UK)
using a chromagenic substrate, 2-chloro-p-nitrophenol linked with maltotriose. The intra-assay CV
was 2.5%.
5.3.5 Statistical Analysis
A sample size of ten participants was estimated using previous data examining the effects of
environmental stress on immune indices (Costa et al. 2010; Laing et al. 2008; Oliver et al. 2007).
One way fully repeated measures ANOVA were performed on pre-experimental body composition
measures. Two-way fully repeated measures ANOVA were performed on saliva parameters
(Chapter 3).
72
5.4 Results
5.4.1 Thermoregulatory (Trec and Tsk) and metabolic responses
Core and mean skin temperature values were analysed using mean scores for n = 10 and n = 15 on
SL and UN. Given n = 10 completed all four trials and significance scores were not different for the
two trials completed by n = 15 and n = 10, n = 10 was used in order to be able to compare all trials
(SL, UN, PEX and TC). Core and mean skin temperatures were lower after cold air tests than at
baseline (Trec, F (12, 168) = 8.955, P = 0.000, η2 = 0.610; Tsk, F (12, 168) = 227.041, P = 0.000, η
2 =
0.058) (Chapter 4). At rest M was not different between either trial (SL: 49 ± 7, UN: 49 ± 11;
PEX: 50 ± 10 W·m2; F (1, 14) = 0.033, P = 0.859, η
2 = 0.997). However, compared with SL, the cold-
induced increase in M was reduced with hypoxic exposure (Table 5.1: F (1, 14) = 21.188, P = 0.000,
η2 = 0.398). RER was higher on UN (Table 5.1: F (1, 14) = 19.478, P = 0.001, η
2 = 0.418).
Table 5.1. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level SL) and at 4000 m before (UN) and after (PEX) acclimatisation on rectal temperature, mean
weighted skin temperature, metabolic heat production and respiratory exchange ratio.
SL UN PEX
Trec at 120 min CAT (°C) 36.9 ± 0.3 36.8 ± 0.3 36.7 ± 0.2
Mean weighted Tsk at 120 min CAT (°C) 29.3 ± 1.0 29.5 ± 1.1 29.8 ± 0.9
M at 120 min CAT (W·m2) 118 ± 44 69 ± 13
† 83 ± 20
†
RER at 120 min CAT 0.81 ± 0.11 1.05 ± 0.14† 0.85 ± 0.09
Values are mean ± SD. † significant difference vs. SL (P < 0.05).
5.4.2 Heart rate and arterial oxygen saturation
Heart rate was higher in UN compared to PEX but was not different to SL (SL: 57 ± 11, UN: 60 ±
910, PEX: 54 ± 9 beats·min-1
; F2, 18 = 7.254, P = 0.005, η2
= 0.385). Arterial oxygen saturation
however, was lower during UN compared to SL but was unchanged during PEX, albeit values on
73
PEX were still low (SL: 98 ± 2, UN: 86 ± 6 PEX: 91 ± 5 %; F (1, 14) = 71.704, P = 0.000, η2 =
0.163).
5.4.3 Saliva IgA and amylase responses
A decline in s-IgA concentration was demonstrated following baseline measures (Figure 5.1: F (3,
42) = 9.540, P = 0.000, η2 = 0.595). No interactions were observed for s-IgA concentration (F (3, 42) =
0.564, P = 0.642, η2 = 0.961) or secretion rate (F (3, 42) = 1.164, P = 0.335, η
2 = 0.923). However, an
interaction was found where saliva flow rate increased from baseline throughout cold exposure
during SL but was suppressed with hypoxia in UN (Figure 5.1: F (3, 42) = 2.873, P = 0.047, η2 =
0.118). There were no observed differences in any saliva parameter between UN and PEX or SL
and PEX. Saliva flow rate was less during SL and UN compared with TC but PEX was not (Figure
5.1: F (3, 24) = 3.859, P = 0.022, η2 = 0.325).
Hypoxia and cold exposure conferred no further increases in α-amylase concentration compared
with cold only (Figure 5.2: F (2, 18) = 0.490, P = 0.621, η2 = 0.052). Compared with TC however,
cold exposure, with or without hypoxia, increased amylase concentration almost three-fold by the
end of the CAT (Figure 5.2: F (3, 24) = 5.957, P = 0.003, η2 = 0.427). Nonetheless, α-amylase
secretion rate was not different between trials (Figure 5.2: F (3, 18) = 2.320, P = 0.110, η2 = 0.278).
5.4.4 Results summary
Core and mean skin temperatures were lower after CATs. Compared with SL, the cold-induced
increase in M was reduced with hypoxic exposure. Saliva flow rate increased from baseline
throughout cold exposure during SL but was suppressed in UN. Hypoxia and cold exposure caused
no further increases in α-amylase concentration compared with cold only. Compared with TC
however, cold exposure, with or without hypoxia, increased amylase concentration almost three-
fold by the end of the CAT. For hydration data see chapter 4.
74
Figure 5.1. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ), at 4000 m before ( ■ ) and after (▲ ) acclimatisation, and a thermo-neutral control
(19.5°C) ( ● ) on saliva flow rate (µl·min-1
) (A), s-IgA concentration (µg·ml-1
) (B) and s-IgA
secretion rate (µg·min-1
) (C). Values are mean ± SD. * significant difference vs Baseline, # vs. TC
(P < 0.05).
♦, ■; *
♦, ■; #
A B C A
B
C
Baseline CAT end Immediately after CAT 1 hour after CAT
75
Figure 5.2. The effect of 120 min cold air test (CAT; 15°C) in un-acclimatised participants at sea
level ( ♦ ), at 4000 m before ( ■ ) and after (▲ ) acclimatisation, and a thermo-neutral control ( ● )
on α-amylase concentration (µg·ml-1
) (A) and secretion rate (µg·min-1
) (B). Values are mean ± SD.
* significant difference vs Baseline, # vs. TC (P < 0.05).
A B C
76
5.5 Discussion
The aim of the present study was to examine the effect of hypoxia on saliva responses to the cold
before and after an 18 day altitude expedition. Due to the potential for greater sympathetic nervous
system activity, vasoconstriction of blood vessels at the salivary glands and reduced saliva secretion
(Bishop, 2006), it was hypothesised that hypoxia in the cold, prior to acclimatisation, would evoke
an increase in α-amylase concentration and reductions in saliva flow rate, s-IgA concentration and
secretion rate of greater magnitude than when individuals were exposed to cold only or post-
expedition. In direct contrast to the hypothesis, s-IgA concentration and secretion rate, regardless of
acclimatisation, were not affected by cold or hypoxia and cold. Nonetheless, α-amylase
concentration was increased during cold exposure but was not exacerbated by hypoxia. When un-
acclimatised however, saliva flow rate was reduced in cold and hypoxia compared with normoxia.
Since the effect of acute hypoxia on leukocytes resembles the same effect as exercise, it has been
suggested that exercise and hypoxia-induced changes in leukocyte subpopulations might be
mediated by similar mechanisms involving neuroendocrinological factors (Pedersen and
Steensberg, 2002). Although physiological mechanisms underlying the decline in s-IgA responses
remain unclear, it is likely that both neural and endocrine factors also influence this mucosal
immune response (Pedersen and Steensberg, 2002). Given arterial oxygen saturation was reduced
during un-acclimatised hypoxic exposure in the present study, and remained low following
acclimatisation, it is not unreasonable to suggest both the neural and endocrine systems were
compensating to maintain homeostasis (Mazzeo, 2005), thus explaining the difference in saliva flow
rate compared with normoxia. Temporal skin temperature was higher during hypoxic exposure
(Chapter 4) suggesting cerebral blood flow may have been increased. This may have been a
subsequent effect of increased neural and endocrine activity in an environment of reduced oxygen.
Future research should look to examine cerebral blood flow in hypoxia to help further understand
mechanisms to maintain homeostasis.
77
The absence of hypoxia-induced s-IgA and α-amylase alterations to cold suggests the mucosal
immune system is robust to a combination of environmental stressors, and as such common URTI
complaints are not likely to be related to the mucosal system upon arrival to high altitude or
following a prolonged stay. Nonetheless, given α-amylase concentration and secretion rate were
affected by cold, regardless of hypoxia, and saliva flow rate was only affected by hypoxia when un-
acclimatised, it is possible there is an increased risk of URTI for new arrivals at altitude if
temperatures are particularly low.
A study to examine the effects of a live high – train low (LHTL) training camp on mucosal
immunity reported similar s-IgA changes from baseline after the first 12 days of training in both the
control (i.e. lived and trained at 1200 m) and LHTL (groups lived at 2500 m or 3000 m and trained
at 1200 m) groups (Tiollier et al. 2005). However, after the last 6-day phase (when living was at an
altitude of 3500 m) s-IgA concentration decreased more in the LHTL group compared with the
2500 and 3000 m phases. It has been suggested that an altitude of 3500 m corresponds to a
threshold that physiological changes intended to tolerate the drop in the partial pressure of oxygen
fail to fully compensate the effect of hypoxia (Colin et al. 1999). Thus, it was speculated that at or
above this altitude the adverse effect of hypoxia on s-IgA responses is more substantial (Tiollier et
al. 2005). In the present study, participants were exposed to an altitude equal to 4000 m while at
rest and displayed no alterations in s-IgA regardless of acclimatisation status. Therefore, it is more
likely the observed changes in s-IgA during the last phase of an 18 day LHTL training camp were
not due to the level of hypoxia per se, or as a result of chronic exposure, but more likely a
cumulative effect of intense physical training at altitude. Had there been an exercise element during
cold air tests of the present study, participants may have demonstrated greater changes in s-IgA and
α-amylase. Further, it might have been clearer to see whether acclimatisation reduced such changes.
Additionally, the normobaric nature of the altitude exposures discussed here does not fully replicate
typical high altitude conditions. It is plausible to suggest that if barometric pressure was also
78
reduced to reflect the real value coinciding with that level of altitude (i.e. 661 mmHg at 4000 m),
the impact on homeostasis and subsequent mucosal immune status may be greater during cold
exposure.
Given that salivary secretion is under neural control (Chicharro et al. 1998) and chronic hypoxia has
been shown to cause marked activation of the sympathetic nervous system (Chicharro et al. 1998;
Calbet, 2003; Zaccaria et al. 2004; Tiollier et al. 2005), this provides the physiological basis for a
potential involvement of neural factors in the s-IgA changes related to hypoxia. Nonetheless, since
mucosal responses to cold were unchanged in hypoxia compared with normoxia it is concluded that
altitude exposure while at rest, before and following an altitude stay, does not cause disruption to
either sympathetic nervous system activity (Mazzeo et al. 2003) or alpha-adrenergic mechanisms
(Ring et al. 2000). Secondly, the reduction in arterial oxygen saturation accompanying exposure to
acute hypoxia unlikely evokes a physiological or metabolic stress great enough to disrupt mucosal
immune responses to cold at rest. On the contrary, in combination, a cold-induced increase in α-
amylase concentration and a hypoxic-induced reduction in saliva flow rate might increase the risk
of infection for illness-prone, un-acclimatised individuals at higher altitudes (e.g. > 4500m) since
saliva is important for oral washing. With regard to the number of mucosal parameters available for
the assessment of potentially stressful situations, future studies would do well to analyse a wider
variety of such parameters in order to provide clarity and help build a framework of likely mucosal
immune responses in extreme environments (i.e. cold and hypoxia).
79
CHAPTER SIX
Practical Field Methods for the Pre-hospital Management of Hypothermia: Shivering Cold
Casualties
6.1 Abstract
The aim of this study was to examine thermoregulatory responses of shivering men to four re-
warming treatments. Seven males completed five randomised trials. These included a thermo-
neutral control trial (TC) and four cold trials. On each cold trial, participants were cooled to 36°C
core temperature. They then completed a 3-hour cold air test (CAT, 0°C) in one of four field
methods; 1. Single layer polythene survival bag (PB), 2. PB with 70°C hot drink in insulated
contatiner (PB+HD), 3. triple-layered metallised Blizzard survival bag with cells to trap and reflect
heat (BB), and 4. BB with chemical heat pads (BB+HP). Core and mean skin temperature,
metabolic heat production and thermal comfort were assessed. Prior to CAT, time to 36°C was not
different (P = 0.50). Compared with PB and PB+HD, skin temperature was greater (PB 25 ± 1,
PB+HD 25 ± 1, BB 27 ± 2, BB+HP 28 ± 2, TC 32 ± 1 °C, P < 0.01) and metabolic heat production
lower during BB and BB+HP (PB 133 ± 73, PB+HD 149 ± 74, BB 112 ± 73, BB+HP 96 ± 62, TC
57 ± 16 W∙m2, P < 0.01). Thermal comfort was higher in BB+HP (cold) compared with PB+HD
(very cold) (P < 0.05). Despite cold exposure, all methods supported re-warming to resting core
temperatures in shivering casualties. However, less metabolic heat production was required to
promote core temperature in triple-layered metallized survival bags compared with polythene
survival bags. Hot drinks had no thermoregulatory or thermal comfort benefit.
80
6.2 Introduction
It is known that exposure to cold with hypoxia may induce greater health risks with regard to
thermoregulatory homeostasis (Chapter 4). However, hypoxia aside, it is not clear whether these
changes would be more severe with harsher conditions that induce mild hypothermia, and whether
they can be treated appropriately with simple cold protection methods available for use in the field.
Accidental hypothermia affects approximately 10% of casualties reported in mountainous
environments and is a significant contributor to fatalities (Sallis and Chassay, 1999; Sharp, 2007).
Although mortality rates are relatively low with severe non-trauma related hypothermia (<28°C),
they rise alarmingly with traumatic injury where mortality is 40, 69 and 100% at 34, 33 and 32°C,
respectively (Moss, 1986; Jurkovich, 1987). Trauma is a frequent medical problem observed in
mountainous environments, accounting for approximately 40% of all emergency call outs and 80%
of all rescues (Hearns, 2003). Rescue times for casualties depend on global location and weather
conditions. Yet even where distances are relatively short between emergency services and a
casualty (e.g. Scottish Highlands) the reported times for evacuation are 2.25 hours by helicopter and
approximately 3.5 hours when individuals are evacuated by others means (e.g. on foot) (Crocket,
1995; Hindsholm et al. 1992). Simple methods that prevent heat loss and promote re-warming that
casualties or first-responders can administer instantly whilst they wait for evacuation will likely
reduce hypothermia related fatalities.
Vapour proof (e.g. polythene) survival bags and metalized plastic sheeting are produced and carried
for emergency use in cold and mountainous environments. These single layer products are also
associated with lower shivering and higher core temperatures in anesthetized patients undergoing
surgery (Buggy and Hughes, 1994; Allen et al. 2010). Contradictory to investigations with human
subjects, where results showed single-layered devices to provide similar thermal protection as
multi-layered devices (Appendix I), an in vitro study where cooling times of pre-heated fluid bags
were compared between different field methods, a multi-layered survival bag (Blizzard Survival™)
81
was shown to be superior at preventing heat loss from fluid filled bags compared with a polythene
survival bag, single layer metalized plastic sheeting or wool blankets (Allen et al. 2010). Further, a
combination of the multi-layered metalized sheeting survival bag (Blizzard Reflexcell™) with
chemical heat pads was shown to be superior to all other methods tested (Allen et al. 2010). Given
the limitations of a fluid filled bag model to simulate the complex thermoregulatory control of
humans, in vivo studies are required to confirm the beneficial effects of a light-weight multi-layer
metalized sheeting survival bag combined with chemical heat pads.
In the field sources of heat are limited to exercise, body-to-body contact, portable warming devices
such as the charcoal burning ‘Heat Pac’, heat pads and the ingestion of warm drinks. Exercise has
been shown to re-warm mildly cold casualties more quickly than shivering alone (Giesbrecht et al.
1987); however, it has obvious limited use for those forced to remain sedentary because of injury,
unconscious state or poor weather. The administration of hot drinks is recommended practice in
shivering cold casualties by the International Commission for Mountain Emergency Medicine
(Durrer et al. 1998); however, to the best of the author’s knowledge, no study has investigated the
efficacy of this practice. Studies investigating the effect of cold beverages indicate core temperature
may be lowered by approximately 0.7°C with the ingestion of one litre of cold fluid (4-7°C) (Imms
& Lighten, 1989; Lee et al. 2008). It is therefore hypothesized that the ingestion of a similar
volume of fluid at 70°C could raise core temperature at least transiently.
Numerous studies have investigated re-warming efficacy of external heat application with results
varying dependent on the amount of heat delivered and the surface area to which the heat is applied
(Daanen et al. 1992; Giesbrecht et al. 1994). In mildly hypothermic casualties capable of normal
shivering, externally applied heat sources (i.e. body-to-body contact and ‘Heat Pac’) have been
shown to be either no better than shivering alone or detrimental to re-warming as they decrease
shivering heat production (Giesbrecht et al. 1987, Giesbrecht et al. 1994). Studies examining these
field methods have completed experiments in thermo-neutral conditions over short periods (<2
82
hours) as opposed to longer exposures in the cold which casualties typically experience awaiting
rescue. It is plausible that in colder conditions, with modest heat sources not applied directly to the
skin, a survival bag containing chemical heat pads (e.g. Blizzard HeatTM
) may confer a significant
advantage for thermoregulation compared with polythene survival bags.
The aim of this investigation was to examine the effectiveness of four practical field methods for
the treatment of cold casualties with a normal shivering response. A secondary aim was to examine
the effect of each field method on long-term energy expenditure and thermal comfort.To simulate
real-life awaiting-rescue events these methods were studied in a cold environment (0°C) following
the reduction of core temperature with cold water immersion to 36°C. It was hypothesised that the
core re-warming rate (°C/h) would be greatest in the Blizzard Heat bag with the chemical heat pads,
followed by the Blizzard survival and polythene survival bag with hot drink. Polythene survival bag
alone was hypothesised to be the least effective method of re-warming.
83
6.3 Method
6.3.1 Participants
Seven healthy males (mean ± SD: age, 21.4 ± 2.6 years; height, 177.8 ± 5.1 cm; nude body mass,
70.5 ± 5.2 kg; body surface area, 1.87 ± 0.10 m2; body fat, 9.9 ± 3.0 %) volunteered to participate in
this study which received local Ethics Committee approval. Prior to commencing trials participants
completed weekly medical reports (Appendix H) to ensure the absence of illness prior to and
during the experiemental period and informed written consent.
6.3.2 Study design
Separated by 7 days, participants completed five randomised experimental trials (Research
Randomiser; www.randomizer.org). The field re-warming interventions were a polythene bag (PB)
(Giesbrecht et al. 1987), a polythene bag with a hot drink (PB+HD), Blizzard survival bag (BB) and
Blizzard survival heat bag (BB+HP). The fifth trial was a thermo-neutral control (TC) where
participants remained seated in an ambient temperature 20.2 ± 1.7°C.
6.3.3 Experimental procedures
The day prior to each experimental trial participants ingested water equal to 35 ml·kg-1
body mass
and the same meals. After an overnight fast and having consumed no caffeine or alcohol within 10
hours participants arrived to the laboratory, euhydrated at 0800 hours. After voiding bladder and
bowels anthropometric measures of height and body mass were obtained. Body composition was
also assessed (Chapter 3).
Following pre-trial measures, participants began a 30 minute seated rest in a thermo-neutral (TN)
environment (ambient temperature: 19.2 ± 1.1°C; relative humidity (RH): 41 ± 6%). Core
temperature (Trec) was measured continuously and recorded every 5 minutes. Metabolic heat
production (M) was assessed every 10 minutes and calculated via indirect calorimetry methods.
84
Thermal comfort (Hollies and Goldman, 1977) and pain sensation (Chen et al. 1998) were also
recorded every 5 minutes. During TC the initial 30 minute rest period was followed by an
additional 30 minute rest period.
After the 30 minute seated rest on cooling trials participants were immersed up to the axilla in 13.0
± 0.1°C stirred water wearing swim shorts until core temperature reduced to 36°C. During cold
water immersion Trec, M, thermal comfort and pain were recorded every 5 minutes. Upon removal
from water participants dressed in dry shorts, socks and gloves prior to entering the environmental
chamber (0°C, RH 40% and wind velocity 0.2 m.s-1
: Delta Environmental Systems, Chester, UK).
Socks and gloves were prescribed based upon results of pilot work which demonstrated pain at the
extremeties may cause necessary withdrawal. After 5 minutes seated, participants were given one of
four interventions which covered whole body and head, then remained seated for the 3 hour CAT or
until core temperature reached 35°C. During Blizzard Heat trials heat pads were placed evenly to
the bag with Velcro adhesive and not placed directly onto skin to avoid contact with skin
thermistors. Unlike supine rest in Chapter 4, a seated position was adopted in order for blood and
saliva samples to be collected most efficiently. During field interventions participants consumed
flavoured water of trace nutritional value in volumes equal to 6 ml∙kg-1
body mass at 0, 60 and 120
minutes. Participants consumed beverages within 15 minutes which were served in insulated drinks
containers to minimise heat loss. During PB+HD beverages were served at 80°C whilst on other
trials were 36°C. No food was provided during CATs. During the CAT Trec, skin temperature (Tsk),
thermal comfort and pain sensation were recorded every 5 minutes. Skin temperature was recorded
at eight sites using skin thermistors. Weighted mean skin temperature was calculated using an area
weighted formula (ISO 9886, 2004). Expired gases were collected every 10 minutes for the
determination of M. Afterdrop period was measured in minutes as the total time taken for an
increase in core temperature following exit of the cold water and entrance to the chamber. Urine
was collected ad libitum from the onset of cold stress until re-warming had commenced. Samples
85
were stored at -40°C and later thawed for analysis of urinary urea nitrogen content (Randox
Laboratories, Co. Antrim, UK). Following CATs participants were immersed up to the axilla in
40°C water until core temperature reached 36°C or 1 hour passed. Participants re-clothed and
consumed a meal (1234 Kcal; CHO 58%, Fat 28%; Protein 14%) (Costa et al. 2010). Following 2
hours seated rest and monitoring, participants left the laboratory. On TC participants sat for the
same time period as in the CATs but freely choose their attire. They were not permitted to eat food
during this period and were required to consume fluids (36°C) equal to 6 ml∙kg-1
body mass at 0, 60
and 120 minutes.
6.3.4 Calculations
The quantity of urinary nitrogen excreted and collected during the entire cold stress period was used
as an index of protein oxidation (Ravussin et al. 1985). The oxidation of carbohydrate and lipid
were assessed by the amount of oxygen consumed per gram of substrate oxidized:
Carbohydrate Oxidation (g·4h-1
) = 4.21 · VCO2 - 2.96 · VO2 - 2.37 · N (eq. 3)
Lipid Oxidation (g·4h-1
) = 1.7 · VO2 - 1.7 · VCO2 - 1.77 · N (eq. 4)
Protein Oxidation (g·4h-1
) = urinary urea nitrogen · 6.25 (eq. 5)
Energy Expenditure (kJ) = 16.18 · VO2 + 5.02 · VCO2 - 5.99 · N (eq. 6)
Nitrogen (N) = urinary nitrogen in grams
6.3.5 Statistical analyses
A sample of six was estimated using rectal temperature data from a previous investigation
(Giesbrecht et al. 1987). To allow for subject incompletion seven participants were recruited. A
one-way fully repeated measures ANOVA was performed on body composition data and on re-
warming parameters. Two-way fully repeated-measures ANOVA (time x trial) were performed on
thermoregulatory and metabolic variables.
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6.4 Results
6.4.1 Preliminary and cold water immersion measures
Throughout the experimental period body mass and composition did not change (Table 6.1: Body
mass: P = 0.496; Body fat: P = 0.631). Participants were always hydrated upon arrival to the
laboratory (Chapter 3). Core temperature prior to cold water immersion was similar in each trial
(Table 6.1: P = 0.881). No trial differences occurred between oxygen consumption or time required
for individuals to reach 36°C (Table 6.1 and Figure 6.3: P = 0.347 and P = 0.496). Oxygen
consumption was greater during cold water immersion compared with seated rest (P = 0.000).
When analysed for order of trial (e.g. trial 1 vs. 4) there were no differences Trec (P = 0.917) or time
to 36°C (P = 0.660) suggesting that a single weekly cold water immersion evokes no cold
acclimatisation.
Table 6.1. Body composition and resting core temperature (Trec) immediately prior to cold water
immersion and time taken to reach 36°C during the cold water immersion.
Trial Body Mass (Kg) Body Fat (%) Mean Trec during
30min rest (°C)
Time to 36°C (mins)
PB 70.4 ± 5.5 9.5 ± 3.3 36.7 ± 0.2 28 ± 11
PB+HD 70.4 ± 5.8 9.6 ± 2.4 36.6 ± 0.2 28 ± 11
BB 70.2 ± 6.0 10.1 ± 3.8 36.7 ± 0.2 35 ± 19
BB+HP 71.0 ± 5.4 10.4 ± 3.0 36.7 ± 0.3 36 ± 18
TC 70.5 ± 5.1 9.8 ± 3.1 36.7 ± 0.2 N/A
Results are means ± SD, n = 7. Abbreviations: PB, polythene survival bag; PP+HD, hot drink plus
polythene survival bag; BB, Blizzard™ Survival bag; BB+HP, Blizzard Heat™ Survival bag; TC,
Thermo-neutral control; N/A, not applicable.
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6.4.2 Cold Air Test Results
Initial re-warming (0-30 mins post cold water immersion)
There were no significant differences in re-warming parameters between the four interventions
(Table 6.2). Skin temperature was however higher during the first hour on BB and BB+HP
compared with PB and PB+HD (Figure 6.2: P = 0.001). Additionally in the first hour, metabolic
heat production was similar in BB and BB+HP compared with TC; whereas it was higher in PB and
PB+HD (Figure 6.3: P = 0.028).
Table 6.2. A summary of re-warming parameters
Trial Afterdrop
magnitude (°C)
Time to afterdrop
nadir (mins)
Afterdrop period
(mins)
Re-warming
rate (°C∙h-1
)
PB 0.55 ± 0.28 20 ± 13 76 ± 61 0.39 ± 0.11
PB+HD 0.61 ± 0.21 21 ± 12 93 ± 63 0.37 ± 0.14
BB 0.51 ± 0.13 24 ± 19 74 ± 41 0.34 ± 0.10
BB+HP 0.62 ± 0.26 19 ± 18 84 ± 58 0.37 ± 0.12
Results are means ± SD, n = 7. Statistics: Afterdrop magnitude, F(3,18) = 0.610, P = 0.617, η2 =
0.092; Time to afterdrop nadir, F(3,18) = 0.311, P = 0.817, η2 = 0.045; Afterdrop period, F(3,18) =
0.439, P = 0.728, η2 = 0.068; Re-warming rate, F(3,18) = 0.522, P = 0.673, η
2 = 0.082. Effect sizes
(η2) interpreted as small (0.01), medium (0.06) and large (0.14) (Cohen, 1988).
6.4.3 Longer Term Cold Protection (30 – 180 mins): Core and skin temperature
Compared with the TC, Trec was lower in all cold trials (F(32,192) = 7.936, P = 0.000, η2
= 0.112).
However there were no Trec differences during cold exposure between the four interventions. All
methods returned Trec to within normal resting core temperature by 180 min. Mean weighted skin
temperature (Tsk) was higher TC compared to re-warming trials (Figure 6.2: F(24,144) = 10.039, P =
88
0.000, η2
= 0.044). By 10 minutes into the cold air test all practical field methods had increased Tsk
compared to 0 minutes (P = 0.000). However compared with PB and PB+HD, Tsk was higher from
30 minutes on BB and BB+HP. There were no differences between BB and BB+HP or PB and
PB+HD.
Figure 6.1. The effect of 180 minute cold air test (CAT; 0°C) on core temperature in four field cold
casualty interventions and a thermo-neutral control. TN; thermo-neutral, End CWI; end of cold
water immersion. Values are Means ± SD. * significant difference vs. TC (P < 0.05).
89
Figure 6.2. The effect of 180 minute cold air test (CAT; 0°C) on mean weighted skin temperature
in four field cold casualty and a thermo-neutral control. Values are Means ± SD. * significant
difference vs. TC, † significant difference vs. PB, ‡ significant difference vs. PB+HD (P < 0.05).
6.4.4 Metabolic Responses
Metabolic heat production was higher than TC on all cold trials at the end of the cold water
immersion and at 0 min of the cold air test (Figure 6.3: F(32,192) = 10.599, P = 0.000, η2
= 0.158).
Metabolic heat production remained higher than TC in PB (10-30 min) and PB+HD (10-180 min).
In contrast, no differences occurred between TC and BB or BB+HP from 10-180 min. However,
cold exposure increased the oxidation of carbohydrates 3 fold during PB, PB+HD and BB+HP
above TC. Despite this, carbohydrate oxidation during BB was not different to other trials (Figure
6.4: F(4, 24) = 3.809, P = 0.016, η2
= 0.388). Regardless of cold exposure, the oxidation rate of lipids
90
was not different between any trial (Figure 6.4: F(4, 24) = 0.992, P = 0.432, η2
= 0.142). However,
while not statistically significant, protein oxidation in the cold tended to be greater than TC (Figure
6.4: F(4, 24) = 2.690, P = 0.055, η2
= 0.310). Energy expenditure from the onset of cold stress was
greater PB+HD compared to all other trials (Figure 6.5: F(4, 24) = 52.240, P = 0.000, η2
= 0.310).
Energy expenditure during BB and BB+HP were not different (P = 0.079), however values were
less than PB (P = 0.025) yet greater than TC (P = 0.001).
Figure 6.3. The effect of 180 minute cold air test (CAT; 0°C) on metabolic heat production in four
field cold casualty interventions and a thermo-neutral control. TN; thermo-neutral, End CWI; end of
cold water immersion. Values are Means ± SD. * significant difference vs. TC, † significant
difference vs. PB, ‡ significant difference vs. PB+HD (P < 0.05).
91
Figure 6.4. The effect of 180 minute cold air test (CAT; 0°C) on substrate oxidation in four field
cold casualty and thermo-neutral control. Values are Means ± SD. * significant difference vs. TC (P
< 0.05).
*
*
*
PB PB+HD BB BB+HP TC
92
Figure 6.5. The effect of 180 minute cold air test (CAT; 0°C) on energy expenditure in four field
cold casualty interventions and thermo-neutral control. Values are Means ± SD. * significant
difference vs. TC, † significant difference vs. PB, ‡ significant difference vs. PB+HD (P < 0.05).
6.4.5 Thermal comfort and pain sensation
Thermal comfort was higher throughout TC compared to the cold trials (Figure 6.6. F(32,192) =
3.734, P = 0.000, η2
= 0.071). Following 30 minutes of cold exposure thermal comfort was higher
during BB+HP compared with PB+HD (P < 0.05). Pain sensation was lower during TC compared
to all cold trials (Figure 6.5. F(32,192) = 3.880, P = 0.000, η2
= 0.077).
* * ‡
*†‡
*†‡
PB PB+HD BB BB+HP TC
93
Figure 6.6. The effect of 180 minute cold air test (CAT; 0°C) on thermal comfort in four field cold
casualty interventions and a thermo-neutral control. Values are Means ± SD. * significant
difference vs. TC, ‡ significant difference vs. PB+HD (P < 0.05).
94
Figure 6.7. The effect of 180 minute cold air test (CAT; 0°C) on pain sensation in four field cold
casualty interventions and a thermo-neutral control. Values are Means ± SD. * significant
difference vs. TC (P < 0.05).
6.4.6 Results summary
Core temperature returned toward normal following three hours in all field treatments. Mean skin
temperature however increased faster and was maintained at a higher level during both Blizzard
trials. Metabolic heat production, thermal comfort and pain sensation were most similar to TC
during BB+HP. Energy expenditure was less during BB+HP compared with any other treatment.
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6.5 Discussion
The results of this investigation imply that the four interventions supported rewarming to near
normal resting core temperatures of shivering cold casualties within three hours of cold exposure.
Although typical rewarming parameters were not different between either intervention metabolic
heat production was greater in polythene compared with the Blizzard survival bags during the first
hour of cold exposure. Furthermore, re-warming in the Blizzard survival bags was achieved with
lower total energy expenditure which may be beneficial for long term survival (Tikuisis, 1995;
Tikuisis et al. 2002).
As anticipated multi-layer, metalized sheeting survival bags led to thermoregulatory advantages
compared with the polythene survival bag with or without a hot drink. The administration of hourly
hot drinks (~430 ml) seemed to confer no advantage in re-warming or the maintenance of core or
skin temperature during cold exposure when compared with polythene survival bags alone. It has
been reported that provided shivering is not contraindicated, core re-warming rate is not different in
cold individuals using either active or passive rewarming devices (Williams et al. 2005). In
contrast, Blizzard survival bags maintained a higher skin temperature throughout the cold air test
which is indicative of superior cold protection and may be speculated to indicate a lower likelihood
of peripheral cold injury. On the contrary, while vasoconstriction reduces heat loss from the skin,
the reduced peripheral blood flow also increases tissue insulation helping to maintain core
temperature (van Ooijen et al. 2005; Toner and McArdle, 1986). The application of external heat
sources to the skin of an individual in the cold may blunt the vasoconstrictive response forcing heat
to be transferred from the core to the skin (Grant et al. 2002). Furthermore, cutaneous temperatures
greater than 29°C reduce peripheral thermo-receptor activity resulting with inadequate stimuli to
activate shivering (Vokac and Hjeltnes, 1981; Rennie, 1988; Mercer. 1991). When shivering is
blunted through peripheral warming in a severe cold environment, heat loss may exceed heat
production (Giesbrecht et al. 1994; Grant et al. 2002). In the present study however, cutaneous
96
temperatures of participants never exceeded this threshold compared with normothermic individuals
in earlier work (Grant et al. 2002). As a result, vasoconstriction was not blunted and as such, large
amounts of heat were not transferred from the core to the periphery, thus these methods provided a
more efficient heat source by conserving more heat.
Upon initial exposure to the cold, metabolic heat production was increased compared to thermo-
neutral in all rewarming trials. By 90 minutes however, metabolic heat production had decreased on
the Blizzard Heat trial to within thermo-neutral control values that were approximately 40% lower
than those recorded during the polythene survival bag trials. Co-incidentally, heat production during
polythene survival bag trials fluctuated throughout, that may reflect greater shivering thermogenesis
(van Ooijen et al. 2005). Since warming of peripheral thermo-receptors reduces shivering and
blunts metabolic heat production (Giesbrecht et al. 1987), cooler skin temperatures demonstrated
during both polythene survival bag trials may have stimulated a greater thermo-receptor response
and thus, shivering activity. Comparatively, during Blizzard Heat the warmer skin temperatures
provided less stimulation to activate shivering and therefore produced less metabolic heat
production. This has been considered detrimental for maintaining heat balance in a cold casualty
(Giesbrecht et al. 1987; Giesbrecht et al. 1994). However, if cold exposure is not recognised by the
body as severe shivering will not begin (Vybiral et al. 2000). Cold protection provided by the
Blizzard Heat survival bag may therefore reduce the amount of heat an individual needs to produce
through shivering and non-shivering thermogenesis. Given the amount of noise produced by
survival bags in contact with the skin, it was not ecological to measure shivering via
electromyography in this study. Nonetheless, metabolic heat production provides a clear indication
of how much extra the body needed to work in order to maintain core temperature. Addtionally,
participants subjectively rated the amount of cold induced pain they felt in each bag which gave a
representation of their perception of physical output needed to keep warm.
97
While survival depends on the capacity to counterbalance the rate of heat loss by increasing
thermogenic rate (Haman, 2006), Blizzard survival bags may have significant benefit in longer term
survival where food sources might be restricted and finite. Specifically, the lower cold-induced
energy expenditure during the Blizzard Heat trial coupled with a continuous increase in core
temperature likely provides a more efficient re-warming effect whereby energy is preserved and
fatigue from excessive shivering is reduced (Martineau and Jacobs, 1988; Vallerand and Jacobs
1989; Vallerand et al. 1993). As a likely consequence of the superior cold protection provided by
Blizzard Heat, perceptual measures (i.e. thermal comfort and pain) tended to be better during the
cold air test compared with when individuals were in the polythene survival bag. In combination
with previous in vitro results (Allen et al. 2010) it is speculated that where cold casualties have
impaired shivering, Blizzard survival bags would also provide superior cold protection including re-
warming capacity compared to polythene survival bags. Future studies where shivering activity is
blunted either medically, or through the use of thermal manikins would help determine this
superiority. An investigation with the superior rewarming interventions compared to no protection
in more severe conditions would also identify any further strengths or weaknesses. To conclude, in
contradiction to the hypothesis, all four of the cold treatment methods tested in 0°C, assisted
shivering cold casualties to increase core temperature to normothermia within the same 3 hour
period. Nonetheless, of the four methods the Blizzard Heat survival bag was the most efficient for
field rewarming given a reduced metabolic heat production was required to increase core
temperature.
98
CHAPTER SEVEN
Salivary IgA and Amylase Responses to Mild Hypothermia and Prolonged Cold Exposure
7.1 Abstract
The aim of this study was to examine the effect of mild hypothermia and prolonged cold exposure
upon s-IgA and α-amylase responses. Twelve males completed two experimental trials which
included a thermo-neutral control (TC) and a cold trial (COLD). On COLD, participants wore
shorts only and were cooled to 36°C core temperature (Trec) in 13°C water. They then completed a
3-hour cold air test (CAT, 0°C) with a polythene survival bag to prevent core temperature
decreasing beyond ethical guidelines. Unstimulated whole saliva samples were collected at
baseline, lowest Trec, 1 h CAT, 2 h CAT and immediately after, 1 h and 3 h after CAT. An
interaction was observed for saliva flow rate and s-IgA secretion rate (F(6,66) = 3.379, P = 0.006;
F(3.086, 33.947) = 3.697, P = 0.020, respectively). Saliva s-IgA secretion rate was significantly lower
during COLD compared to TC (P < 0.05). Compared with lowest Trec, saliva s-IgA secretion rate
was higher at 1 and 3 h post CAT (P < 0.05) during COLD, but no differences occurred throughout
TC. Saliva flow rate was significantly lower during the first hour of CAT during COLD compared
with TC (P < 0.05) and remained lower until 3 h post. Saliva s-IgA concentration was significantly
reduced following baseline measures on both cold and thermo-neutral trials (P < 0.01), whereas α-
amylase concentration was greater throughout CAT compared to TC until re-warming had occurred
(P < 0.05). These results suggest a reduction in core temperature (≥ 1.5°C) resulting from cold
water immersion and subsequent cold air exposure alters the usual daily saliva responses which may
increase susceptibility to illness and infection (i.e. URTI, common colds, influenza) if re-warming
is not initiated immediately.
99
7.2 Introduction
It is known that exposure to cold with hypoxia may induce greater health risks with regard to
mucosal immunity compared to exposure to cold alone (Chapter 5). However, it is not clear
whether these changes would be more severe in colder conditions that induce mild hypothermia.
Furthermore, current knowledge in this area has not been verified in accordance with diurnal
fluctuations and thermal-neutral control trials for comparison.
It is the popular belief that most common colds occur because the host is exposed to a cold
environment beforehand (Dowling et al. 1958; Biggar et al. 1984). However, a direct causal relation
between getting cold and developing an infection remains to be clarified (Lavoy et al. 2011). Cold
exposure has been associated with an increased incidence of bronchorrhea, sinusitis, and upper
respiratory tract infections (URTI) (Clothier, 1974; Giesbrecht, 1995; Castellani et al. 2002; Lavoy
et al. 2011). However, much of this research has examined individuals undertaking intense physical
activity in the cold (i.e. athletes and military personnel). Cold-induced decrements in immune-
surveillance are a particular problem for physically active individuals (Brenner et al. 1999). For
example, URTIs are the main cause of illness and missed practise in elite cross country skiers
(Berglund and Hemmingson, 1990). Nonetheless, the risk of illness or infection for those forced or
required to remain sedentary in the cold, due to injury or adverse weather, for a prolonged period of
time is unknown.
It has been suggested that a continuum exists for the effects of body core cooling on immune
function whereby mild decreases in body core temperature have little stimulatory effects on
immune function, but more severe decreases have depressive effects (Costa et al. 2010). However,
it remains to be shown whether large (≥ 1.5°C) reductions in body core temperature suppress
mucosal immunity and increase the likelihood of infection (Costa et al. 2010).
100
A decrease in the saliva concentration of s-IgA accompanies an increased susceptibility to URTI
(Gleeson et al. 1999; Hanson et al. 1983; Nieman and Nehlsen-Cannarella, 1991). However,
breathing cold dry air itself can elicit symptoms similar to these infections, such as a persistent dry
cough and nasal mucosal drying (Silvers, 1991; Giesbrecht, 1995). Thus it may be that cold weather
negatively impacts the respiratory system independently of changes in immunity. For example,
performing prolonged exercise in freezing cold conditions did not influence saliva flow rate or s-
IgA secretion rate responses (Walsh et al. 2002). However, modest whole body cooling (Trec
35.9°C) at rest showed reduced s-IgA responses (Costa et al. 2010). Unfortunately, a lack of a
thermo-neutral control trial for comparison means changes may reflect diurnal variation of saliva
concentrations (Walsh et al. 2002). The influence of prolonged cold exposure upon s-IgA and α-
amylase responses in clinically hypothermic individuals (Trec 35°C) has received little attention. In
the field, cold stress may evoke suboptimal host defence that subsequently may increase the risk of
illness and infection (Johnson et al. 1977; Houben et al. 1982; Hiramatsu et al. 1984).
Evidence to date indicates that a mild decrease in core body temperature (Trec decrease ~ 0.5°C)
during short (30 min) (Lackovic et al. 1988) or prolonged (2 h) (Brenner et al. 1999) cold air
exposure can have immuno-stimulatory effects. During short cold air exposures (4°C) natural killer
cell activity was found to increase (Lackovic et al. 1988). The immersion of healthy males in cold
water (14°C) has been shown to induce a leukocytosis (Jansky et al. 1996). However, it is unknown
what core temperature participants presented with during and following these immersions.
Therefore, little information is available from controlled laboratory studies regarding any immuno-
stimulatory effects of a decrease in core temperature ≥1.5°C. Further, it remains unclear how
prolonged (3 h) cold air exposure in combination with such a decline in core temperature effects s-
IgA and α-amylase responses. Previous explanations for the disruption to mucosal immunity
observed with modest whole-body cooling at rest have included: cold air decreasing the temperature
of mucosal membranes, the subsequent drying effect which may reduce mucociliary clearance and
101
phagocytic activity (Eccles, 2002), and a cooling-evoked neuro-endocrine regulation of trans-
epithelial s-IgA translocation (Giesbrecht, 1995; Proctor and Carpenter, 2007).
The aim of the present study, therefore, was to examine the effect of mild hypothermia and
prolonged cold exposure on s-IgA and α-amylase responses. It was hypothesised that mild
hypothermia and cold exposure would lower s-IgA and amylase secretion in comparison with
normal responses in a thermo-neutral environment. Given it would be unethical to expose
participants to cold without some form of thermal protection, the polythene bag was chosen as it
offers minimal warmth to the body inside compared with other devices (Chapter 6) and therefore
would prevent a blinding of the effects of cold on immune function.
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7.3 Method
7.3.1 Participants
Twelve healthy males (mean ± SD: age, 20.7 ± 2.2 years; height, 177.5 ± 6.6 cm; nude body mass,
68.6 ± 6.4 kg; body fat, 10.9 ± 3.7%) participated in this study. Participants gave written consent
and medical history before the study, which received local Ethics Committee approval. Participants
also completed the Wisconsin Upper Respiratory Symptom Survey (Appendix H) two weeks prior
to and during the experimental period.
7.3.2 Preliminary measurements
Before each experimental trial participants arrived at the laboratory after an overnight fast having
consumed no food, caffeine or alcohol within 10 h. Participants ingested water equal to at least 35
ml·kg-1
body mass the day prior to each trial. After voiding bladder and bowels, nude body mass
and height were measured. Using segmental multiple frequency bioelectrical impedance measures
of body fat were obtained.
7.3.3 Experimental Trials
Separated by 7 d, participants completed two randomised experimental trials (Research
Randomiser; www.researchrandomizer.org). The two trials were: cold exposure with a polythene
survival bag (COLD) and a thermo-neutral control trial (TC). A polythene survival bag was
necessary to prevent core temperature falling to below mild hypothermic levels. Following pre-trial
measures participants began each experimental trial at 0800. Following 30 minutes seated rest in a
thermo-neutral environment (ambient temperature: 19.2 ± 1.1°C; relative humidity: 40.9 ± 6.0%),
the first saliva sample was collected.
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For the cold trial participants were immersed in 13.0 ± 0.1°C stirred water up to the axilla wearing
swim shorts only until core temperature reduced 36°C. Upon removal from the water and after
drying, participants entered the chamber where they remained seated for a 3 h cold air test (Dry
bulb temperature (Tdb) of the chamber remained constant at 0°C with a relative humidity (rh) 40%
and 0.2 m.s-1
wind velocity; Delta Environmental Systems, Chester, UK). Once in the chamber,
participants sat wearing dry shorts only for five minutes before being given the survival bag.
Expired gases were collected every 10 minutes for the determination of M. Saliva was collected at
baseline, lowest Trec, 1 h, 2 h and 3 h during cold exposure. The lowest Trec sample was collected in
the chamber once core temperature showed the first sign of increasing following a distinct afterdrop
phase. Early removal from the chamber occurred if core temperature reduced to 35°C. Following
the cold air test participants were immersed in 40°C water to increase core temperature. After 1 h
participants gave another saliva sample, re-clothed and consumed a meal (1234 Kcal; CHO 58%,
Fat 28%; Protein 14%) (Costa et al. 2010). Following a further 2 h recovery, participants gave a
final saliva sample and were free to leave the laboratory.
All participants completed a control trial to account for diurnal fluctuations in s-IgA concentration
(Gleeson et al. 2001; Walsh et al. 2002). During the control trial participants remained seated in an
ambient temperature of 20.2 ± 1.7°C and wore normal clothing (0.8-1.0 clo / 1.24-1.55 togs). Saliva
samples were collected in the same manner as those in the cold trial.
7.3.4 Saliva collection and analysis
Un-stimulated whole saliva samples were collected using pre-weighed universal tubes (Chapter 3).
Saliva samples were collected while the participant sat quietly in the laboratory. Saliva volume was
estimated by weighing the universal container immediately after collection to the nearest mg. From
this, saliva flow rate was determined by dividing the volume of saliva by the collection time. Saliva
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was aspirated into Eppendorf tubes and stored at -40°C for further analysis. After thawing s-IgA
concentration was determined by ELISA (Salimetrics Europe Ltd, Suffolk, UK) using IgA
monomer from human serum as standard. The intra-assay CV was 2.6%. s-IgA secretion rate was
calculated by multiplying the saliva flow rate by s-IgA concentration.
Alpha amylase concentration was determined by ELISA (Salimetrics Europe Ltd, Suffolk, UK)
using a chromagenic substrate, 2-chloro-p-nitrophenol linked with maltotriose. The intra-assay CV
was 2.1%.
7.3.5 Statistical analyses
A sample size of ten participants was estimated (http://www.dssresearch.com/toolkit/sscalc) using
previous data examining the effects of stress on immune indices (Costa et al. 2010; Laing et al.
2008; Oliver et al. 2007). One way fully repeated measures ANOVA were performed on pre-
experimental body composition measures. Two-way fully repeated measures ANOVA were
performed on saliva parameters.
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7.4 Results
7.4.1 Body mass and composition
Throughout the experimental period body mass and composition did not change (Table 7.1: Body
mass: P = 0.733; Body fat: P = 0.097). Core temperature prior to cold water immersion was similar
in each trial (Table 7.1: P = 0.545).
Table 7.1. Resting core temperature (Trec) immediately prior to cold water immersion and time
taken to reach 36°C during the cold water immersion
Trial Body mass (Kg) Body fat (%) Resting Trec (°C) Time to 36°C (mins)
Cold 68.6 ± 6.4 10.9 ± 3.7 36.8 ± 0.3 29 ± 14
TC 68.7 ± 6.2 11.4 ± 3.7 36.8 ± 0.2 N/A
Results are means ± SD, n = 12. Abbreviations: TC, Thermo-neutral control; N/A, not applicable.
7.4.2 Thermoregulatory and metabolic responses
Compared with the thermo-neutral control, Trec and mean weighted skin temperature (Tsk) were
lower during cold exposure (Table 7.2: F(1.877,15.012) = 4.192, P = 0.038, η2
= 0.113 and F(24,144) =
10.039, P = 0.000, η2
= 0.044, respectively). During the first hour of the cold air test, metabolic heat
production was higher in the cold compared with thermo-neutral (Table 7.2: F(1.073,8.583) = 11.531, P
= 0.008, η2
= 0.083).
Table 7.2. Summary of mean thermoregulatory parameters
Trial Lowest Core
Temperature (°C)
Mean Weighted Skin
Temperature (°C)
Metabolic Heat
Production (W·m2)
COLD 35.4 ± 0.3 25.0 ± 1.3 150 ± 64
TC 36.6 ± 0.3 31.6 ± 1.0 49 ± 11
Results are means ± SD, n = 12.
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7.4.3 Salivary secretory IgA and alpha amylase concentration
Saliva s-IgA secretion rate was lower during COLD at baseline and throughout CAT compared to
TC (Figure 7.1C: P = 0.05). Saliva s-IgA secretion rate however, was similar between the trials
following one hour of recovery from cold exposure. Compared with lowest core temperature, saliva
s-IgA secretion rate was higher at one and three hours post CAT during the cold trial, but no
differences occurred throughout the thermo-neutral control. An interaction was observed for both
saliva flow rate and s-IgA secretion rate (Figure 7.1A: F(6,66) = 3.379, P = 0.006, η2 = 0.280; Figure
7.1C: F(3.086, 33.947) = 3.697, P = 0.020, η2
= 0.417 respectively). A main effect of time was observed
for saliva s-IgA concentration (Figure 7.1B: F(2.93, 32.262) = 7.696, P = 0.001, η2
= 0.386). Saliva flow
rate was lower during the first hour of the CAT compared with thermo-neutral and remained lower
until three hours post CAT. Saliva flow rate was higher three hours post-CAT compared with
lowest core temperature. Following the initial morning sample there were no further changes in
saliva flow rate during the thermo-neutral control. Saliva s-IgA concentration was reduced
following baseline measures on both cold and thermo-neutral trials (P = 0.01).
Saliva α-amylase concentration was greater during COLD throughout CAT compared to TC
(Figure 7.2A: F(1, 8) = 8.506, P = 0.019, η2
= 0.5150). When core temperature was at its lowest
during COLD, α-amylase concentration was at its greatest. At 1h post CAT and 3h post CAT α-
amylase concentration in COLD and TC was the same (P = 0.05). Despite a small increase when
core temperature was at its lowest, saliva secretion rate remained unchanged between TC and
COLD (Figure 7.2A: F (1, 8) = 0.547, P = 0.481, η2 = 0.063).
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Figure 7.1. The effect of 180 min cold air test (CAT; 0°C) on saliva flow rate (µl·min-1
) (A), s-IgA
concentration (µg·ml-1
) (B) and secretion rate (µg·min-1
) (C) in comparison to a thermo-neutral
control. Values are means ± SD. * significant difference vs. thermo-neutral, † significant difference
vs. lowest Trec, ‡ significant difference vs. baseline (P < 0.05).
A
B
C
Baseline
108
Figure 7.2. The effect of 180 min cold air test (CAT; 0°C) on saliva alpha amylase concentration
(µg·ml-1
) (A) and amylase secretion rate (µg·ml-1
) (B) in comparison to a thermo-neutral control.
Values are means ± SD. * significant difference vs. thermo-neutral (P < 0.05).
7.4.4 Results summary
Saliva s-IgA secretion rate was lower during COLD compared to TC. Saliva flow rate was lower
during the first hour of the CAT compared with TC and remained lower until three hours post CAT.
Saliva α-amylase concentration was greater during COLD throughout CAT compared to TC.
B
A
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7.5 Discussion
The aim of the present study was to examine the effect of mild hypothermia and prolonged cold
exposure on mucosal immunity in comparison to a thermo-neutral control trial. This novel design
allowed for the diurnal variation in mucosal parameters to be accounted for. In support of the
hypothesis, mild hypothermia evoked a reduction in saliva flow rate and an increase in α-amylase
concentration which was not due to the time of day samples were collected. Saliva-IgA secretion
rate was lower and α-amylase concentration was higher throughout the cold exposure until re-
warming to within normal resting core temperature values had occurred.
Given the presence of a thermo-neutral control trial, these results extend previous research that
showed whole body cooling (Trec 35.9°C) via cold air exposure (0°C) decreased s-IgA secretion rate
compared to baseline (Costa et al. 2010). Explanations included the effects of cold air reducing the
temperature of the mucosal membranes, a possible drying effect of cold air and whole body
cooling-evoked neuro-endocrine regulation of trans-epithelial s-IgA translocation (Giesbrecht,
1995; Proctor and Carpenter, 2007). The time course of the response suggested that whole body
cooling decreases s-IgA translocation because s-IgA synthesis usually takes many hours to days
(Costa et al. 2010; Hucklebridge et al. 1998). However, such explanations could only have been
speculative owing to an absent control trial. During the present study a more intense cooling
procedure induced mild hypothermia (Trec 35°C) in almost all individuals. The diurnal variation
pattern for s-IgA responses was similar throughout both cold and thermo-neutral conditions.
However, both saliva flow rate and s-IgA secretion rate were markedly suppressed by mild
hypothermia and cold exposure.
Early experiments (Proetz, 1953; Baetjer, 1967) examining beat frequency of cilia in the paranasal
sinuses of rabbits and the trachea of chicks indicated that exposure to cold air decreases the
temperature of the nasal respiratory epithelium and causes a decrease in mucociliary clearance
(Eccles, 2002). A decrease in mucociliary clearance associated with cold exposure has been
110
suggested to increase the predisposition to respiratory infection (Diesel et al. 1991). With this in
mind, throughout each trial, temperature controlled fluid (36°C) was consumed hourly in order to
be able to combine findings with chapter 4. It is plausible that this fluid, similar to body
temperature, may have reduced the drying effect of cold air and maintained the temperature of the
mucosal membranes. It is speculated therefore that these earlier explanations for changes in
mucosal immunity are less likely within the present study and an alternative factor is responsible for
changes in saliva flow rate, s-IgA secretion rate and α-amylase concentration.
A body of literature exists, detailing saliva responses during exercise in the cold (Mylona et al.
2002; Walsh et al. 2002; Costa et al. 2010). However, the present study is the first to observe a
reduction in the saliva flow rate and s-IgA secretion rate but an increase in the α-amylase
concentration of mildly hypothermic, sedentary individuals exposed to the cold. Saliva flow rate, s-
IgA secretion rate and α-amylase concentration were only similar to those levels observed during
thermo-neutral control after three hours of re-warming and consumption of a hot meal. Despite this,
that cold exposure and mild hypothermia disrupt mucosal immunity should be suggested with
caution. This is because the s-IgA secretion rate recorded at rest, prior to cold exposure, was lower
than at that same time during thermo-neutral control. It is possible this was due to an anticipatory
effect of the forthcoming cold water immersion. Psychological stress, defined as the experience of
negative events or the perception of distress, has been shown to alter saliva total protein
concentration, α–amylase activity and IgA concentration (Bosch et al. 1996; Cohen et al. 2001).
Such as, an increase in saliva total protein concentration but a decrease in saliva α-amylase activity
was observed in patients awaiting dental treatment compared with a non-stress situation (Morse et
al. 1983). It is possible that participants in the present study were more anxious upon arrival to the
laboratory on the day they were going to be exposed to the cold compared with when they remained
warm. In future, blinding participants to the experimental trial prior to baseline samples may be
beneficial. On the contrary, after re-warming and a meal, s-IgA secretion rate was greater and α-
111
amylase concentration lower than when participants displayed their lowest core temperature,
whereas no changes occurred throughout the thermo-neutral trial. This suggests that until re-
warming is initiated, cold, sedentary individuals are at risk from increased mucosal immune
disturbance.
In conclusion, a reduction in core temperature resulting from cold water immersion and cold air
exposure alters the usual daily mucosal response which may increase a person’s susceptibility to
illness and infection (i.e. URTI, common colds, influenza), particularly if they are not rewarmed
immediately. In combination with earlier findings (Chapter 5), exsposure to severe cold
environments with hypoxia create an even greater risk for un-acclimatised individuals travelling to
high altitudes. It is necessary for such individuals to practise a programme of constant monitoring to
ensure health is maintained during exposure to extreme environments.
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CHAPTER EIGHT
Practical Field Methods For Cold Protection of Non-shivering Cold Casualties: An in Vitro
Model
8.1 Abstract
The aim of this investigation was to examine the effectiveness of three field methods for non-
shivering cold casualty protection and re-warming. To achieve this, an in vitro fluid bag model was
used to simulate a non-shivering cold casualty. Three field methods were compared with a control
trial (CON). Trials were a polythene bag (PB), a triple-layered, metalised plastic sheeting survival
bag (Blizzard Survival bag (BB)), a triple-layered, metalised plastic sheeting survival bag with heat
pads (Blizzard Heat survival bag (BB+HP)). Cold protection methods were assessed for four hours
in a range of environmental conditions (-18.5°C, 0°C and 18.5°C). Trials began once fluid bag core
temperature had reached 37°C. The effectiveness of the survival bags was assessed by the amount
of core temperature decline in each environmental condition. After exposure to 18.5°C there were
no differences in final Trec between the cold protection methods (P > 0.05). In 0°C, final Trec during
BB+HP was significantly greater than CON (P = 0.004). After 240 minutes in -18.5°C final Trec in
BB+HP was significantly greater than PB (P = 0.019). At 60 minutes of exposure to 18.5°C the
reduction in Trec was significantly greater in PB compared to BB+HP (P = 0.036). Following 120
minutes, the amount of heat lost was significantly greater in PB and BB compared to BB+HP (P <
0.05). The effectiveness of chemical heat pads in combination with a triple layered, metallised
survival blanket may counteract the decline in thermogenesis accompanying the onset of severe
hypothermia and reduce hypothermia related fatalities.
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8.2 Introduction
When a human is hypothermic but has the ability to shiver, core temperature can recover to normal
provided a protective layer is supplied (Chapter 6). Ethical guidelines surrounding hypothermia
research often limit how cold a human can be made. This creates a grey area with regard to
knowledge about how the human body can cope once shivering has ceased and there is no longer
any form of internal heat production. It is pertinent to understand, even if only by the use of a fluid
model, how well an external heat source that can be easily administered in the field, will treat a
body with a core temperature so low that heat production via shivering has ceased.
During cold exposure vasoconstriction and shivering are the main defence against temperature loss
(Holcomb, 2005). However, as core body temperature decreases the adrenergic, cardiovascular and
metabolic mechanisms begin to fail (Farkash et al. 2002). When core temperature reaches 32°C
shivering is terminated (Giesbrecht et al. 1997). Although mortality rates are relatively low with
severe non-trauma related hypothermia (<28°C), they rise alarmingly with traumatic injury where
mortality is 40, 69 and 100% at 34, 33 and 32°C (Moss, 1986; Jurkovic et al. 1987) (Chapter 6). In
military environments, including wartime countries such as Afghanistan, where temperatures
remain fairly mild in the winter, hypothermia is commonly encountered during combat operations
(Marshall, 2005; Moran et al. 2003). Casualty’s air lifted by helicopter experience ambient
temperature drops up to -15°C per 1000 feet of altitude gain (Johnson et al. 2010). This, in
combination with a four hour evacuation flight will likely accelerate the onset of hypothermia.
Additionally, drugs administered to the casualty such as sedatives and opioids decrease the
thermogenic effect of shivering (Kurz et al. 1995; Giesbrecht and Bristow, 1997). Given a non-
shivering casualty presents a more dangerous condition than one who is shivering (Hamilton and
Paton, 1996), simple methods that prevent further heat loss in non-shivering casualties that can be
administered instantly whilst waiting for evacuation will likely reduce hypothermia related fatalities
(Arthurs et al. 2006).
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Studies examining heat loss and field cold protection methods in non-shivering casualties are
limited because of ethical limitations with cooling humans to a state of non-shivering. A recent in
vitro study where cooling times of fluid bags were compared between different field methods
showed a multi-layered survival bag (Blizzard Survival™) to be superior at preventing heat loss
compared with a polythene survival bag, single layer metalized plastic sheeting and wool blanket
(Allen et al. 2010). Further, a combination of the multi-layered metalized sheeting survival bag
(Blizzard Reflexcell™) with chemical heat pads was shown to be superior to all other methods
tested. Nonetheless, given that the exposure conditions did not reflect typical cold temperatures
experienced during outdoor winter pursuits, it remains unknown how well these devices protect
non-shivering, sedentary humans in the cold. Furthermore, trials were terminated before critical
core temperatures were reached. Potentially, the amount of heat loss may increase as time in the
cold continues. More specifically, when shivering is terminated as a result of severe hypothermia,
body heat loss increases. Chemical pads inside a survival bag have obvious advantages in
comparison to alternative active warming devices, such as durability, lightness and adaptability to
many situations (Hamilton and Paton, 1996). However, rescue teams are unaware of an optimal
field treatment method for non-shivering casualties.
The in depth study of severe hypothermia has been difficult given that the experimental study of
humans has mostly been confined to mild hypothermia (Giesbrecht et al. 1997). However, in
clinical situations, the narcotic drug meperidine is commonly used to inhibit post-operative
shivering (Macintyre et al. 1987). With an immediate onset following intravenous administration
and short duration of action, meperidine is particularly desirable for use in experimental research to
effectively abolish shivering during mild hypothermia. Its use in cold exposed humans has resulted
in a three-fold increase in core temperature after-drop and more than a four-fold increase in length
of the after-drop period (Giesbrecht et al. 1997). However, since participants remained in a thermo-
neutral environment following shivering inhibition, it remains unknown how severe the after-drop
115
would be in a cooler environment. The administration of narcotics has helped improve
understanding of severe hypothermia in humans. It is of limited use however, because a medically
trained practitioner must be present at all times. The use of a non-shivering fluid bag model allows
research to be performed in a controlled, safe manner without risk to humans. Albeit, a human body
has a far smaller heat capacity range than that of water in a fluid model, a number of varying
environmental conditions can be applied using this design to gain a better understanding of cooling
rates without requiring human participants.
The aim of this investigation was to examine field cold protection methods for the prevention of
heat loss in a non-shivering casualty model in a range of environmental temperatures (18.5ºC, 0ºC
and -18.5 ºC). To simulate real-life awaiting-rescue events, the field cold protection methods were
studied for a four-hour period with thermo-neutral conditions (18.5°C). It was hypothesised that the
active heating device (Blizzard Heat survival bag) would minimise the reduction in core
temperature in all ambient conditions so that the final core temperature remained higher compared
to the passive devices (Polythene and Blizzard survival bags).
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8.3 Method
8.3.1 Fluid bag model
Two fluid bags were configured to represent a human adult male torso similar to those of human
participants in chapters 4, 5, 6 and 7 (~60% of 70 Kg or 48.6 Kg (Allen et al. 2010)). Each torso
model used one 60 L polyvinyl chloride bag with electrically welded seams and was filled with 48.6
L water pre-heated to 37.5°C. Water was used instead of saline given the ease of access, use and
cost. Models had an indwelling thermistor that represented core temperature and two surface
temperature probes situated on the anterior and posterior.
8.3.2 Study design
Separated by at least 24 hours, each fluid bag completed twelve randomised experimental trials
(Research Randomiser; www.randomizer.org). Four of these trials were performed with three field
cold protection methods that included a polythene bag, a Blizzard Survival bag and a Blizzard
Survival heat bag. The fourth trial was a control where the fluid bag had no protection. Each
method was assessed in -18.5°C, 0°C and 18.5°C.
8.3.3 Experimental procedures
Each fluid bag was filled with heated water to a starting core temperature of 37.5°C. At this
temperature fluid bags were transported into the environmental chamber set to one of the three
experimental temperatures (RH 40% and wind velocity 0.2 m.s-1
: Delta Environmental Systems,
Chester, UK). During each trial, fluid bags were placed on a flexible plastic sheet to prevent direct
contact with the floor. Core temperature was measured continuously and recorded every 5 minutes
using a flexible thermistor inserted to the medial section of the fluid bag. Surface temperature was
also recorded every 5 minutes at two sites using surface thermistors. Water was circulated in the
117
fluid models by manual rotation of the bag every 5 minutes to eliminate temperature gradients
within the bag.
8.3.4 Statistical analyses
A two-way fully repeated-measures ANOVA (time x trial) was performed on thermoregulatory
variables. Significance was accepted at P < 0.05. Where significant main effects and interactions
occurred Post Hoc Tukey’s HSD was used. All data are presented as Mean ± SD.
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8.4 Results
8.4.1 Final Core Temperature
After 240 minutes exposure to 18.5°C there were no differences between the final core temperatures
in any of the trials. However, after 240 minutes in -18.5°C the final core temperature in BB+HP
(26.0°C) was greater than PB (16.5°C) (P = 0.019).
Final core temperatures on CON 0°C and CON -18.5°C were lower than PB 18.5°C (P = 0.03 and P
= 0.048, respectively), BB+HP 18.5°C (P = 0.006 and P = 0.023, respectively) and BB+HP 0°C
(Figure 8.1: P = 0.033). Additionally, final core temperatures in PB -18.5°C and BB -18.5°C were
also lower than PB 18.5°C (P = 0.038 and P = 0.022, respectively). BB+HP in -18.5°C was not
lower than any final core temperature in a warmer ambient condition except BB 18.5°C (P = 0.038)
which was also higher than PB in -18.5°C (P = 0.026).
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Figure 8.1. Final core temperature after 240-minute exposure to 18.5°C, 0°C and -18.5°C in three
field cold casualty interventions and a control. Values are Means ± SD. * significant difference vs.
CON 0°C; † significant difference vs. PB-18.5°C, a significant difference vs. CON 18.5°C, b
significant difference vs. PB 18.5°C, c significant difference vs. BB+HP 18.5°C, d significant
difference vs. BB+HP 0°C, e significant difference vs. BB 18.5°C (P < 0.05).
8.4.2 Hourly change in Core Temperature
At 60 minutes of exposure to thermo-neutral conditions (18.5°C) the reduction in core temperature
was greater in PB compared to BB+HP and continued to increase throughout the remainder, with a
final difference at 240 minutes of 2.9°C (Figure 8.2A: F(3, 3) = 11.890, P = 0.036, η2 = 0.067). The
hourly change in core temperature within each thermo-neutral trial was greater following the initial
core temperature at the onset of exposure (Figure 8.2A: F(4, 4) = 533.447, P = 0.000, η2 = 0.002).
Similarly, a main effect of time in 0°C also established that the hourly change in each trial was
120
greater following the onset of exposure (Figure 8.2B: F(4, 4) = 1638.403, P = 0.000, η2 = 0.001). The
amount of heat loss during CON in 0°C was greater each hour compared to the other trials in that
environment (Figure 8.2B: F(12,12) = 7.584, P = 0.001, η2
= 0.116). No differences occurred between
PB and BB. However, following 120 minutes, the amount of heat lost was greater in PB and BB
compared to BB+HP. The difference continued to increase over each hour so that by 240 minutes
PB and BB had lost 14°C whereas BB+HP had only lost 7.6°C.
Following 60 minutes of exposure to -18°C, core temperature change was greater during CON
compared to all trials (P = 0.05). Exposure to -18°C evoked an interaction whereby BB+HP had the
smallest amount of heat loss at 60 minutes of exposure compared to CON and PB trials (Figure
8.2C: F(12, 12) = 15.364, P = 0.000, η2 = 0.061). The difference in core temperature between these
trials continued to increase at each hour throughout. No difference occurred between BB and
BB+HP until 180 minutes, yet a difference between PB and BB was established an hour earlier and
continued to increase throughout the remainder of the exposure. With each hour following the onset
of cold exposure core temperature heat loss increased in all trials (Figure 8.2C: F(4, 4) = 1314.03, P
= 0.000, η2 = 0.001).
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Figure 8.2 Hourly change in core temperature during 240 minute exposure to A, 18.5°C, B, 0°C
and C, -18.5°C in three field cold casualty interventions and a control. Values are Means ± SD. #
significant difference vs. 0; * significant difference vs. CON; † significant difference vs. PB, ‡
significant difference vs. BB (P < 0.05).
A
B
C
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8.4.3 Predicted Survival for Non-Shivering Cold Casualty
Time to 32°C from 37°C was calculated as an estimate of time to mortality with traumatic injury
(Moss, 1986; Jurkovic et al. 1987). During CON -18.5°C time to 32°C was lower (30 mins)
compared to any other trial (Table 8.1). PB -18.5°C demonstrated a similar time to 32°C as CON
0°C, but was less than CON 18.5°C, PB 18.5°C and BB+HP 18.5°C. The longest time to 32°C from
37°C was observed during BB+HP 18.5°C (230 mins) which was longer than CON 0°C, PB 18.5°C
and CON -18.5°C (P = 0.05) (Table 8.1). Time to 32°C during BB+HP 0°C was the same as PB
18.5°C. Time to 32°C did not differ between BB 0°C and BB -18.5°C. Time to 32°C during
BB+HP -18.5°C was similar to CON 18.5°C. No differences occurred between PB and BB when
exposed to the different ambient temperatures, yet time to 32°C was slightly longer during BB
exposure to 0°C and -18.5°C (Table 8.1).
Following the reduction of core temperature to 32°C, the time to 24°C for each trial was calculated
as an estimate of time from cessation of shivering (non-trauma related hypothermia) to apparent
death (Durrer et al. 1998). Exposure to thermo-neutral conditions (18.5°C) did not cause a reduction
in core temperature to 24°C in any trial (Table 8.1). However, time to 24°C from 32°C was less
during CON in 0°C compared to PB (P = 0.033) and a trend occurred between CON and BB (P =
0.07) (Table 8.1: F(5, 5) = 25.293, P = 0.001, η2 = 0.038). Core temperature did not reduce to 24°C
in any of the temperature controlled environments for BB+HP.
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Table 8.1. Time to 24°C from 32°C during 240 minute exposure to 0°C and -18.5°C.
Values are mean ± SD. a significant difference vs. CON 18.5°C, * significant difference vs. CON
0°C, b significant difference vs. PB 18.5°C,
c significant difference vs. BB+HP 18.5°C,
d significant
difference vs. BB+HP 0°C, f vs. CON -18.5°C (P < 0.05). Abbreviations: N/A, not applicable.
8.4.4 Results summary
After 240 minutes exposure to 18.5°C there were no differences between the final core temperatures
in any of the trials. However, after 240 minutes in -18.5°C the final core temperature in BB+HP
(26.0°C) was greater than PB (16.5°C). The longest time to 32°C from 37°C was observed during
BB+HP 18.5°C (230 mins) which was longer than CON 0°C, PB 18.5°C and CON -18.5°C. Core
temperature did not reduce to 24°C in any of the temperature controlled environments for BB+HP.
Trial Time from 32°C to 24°C (mins) Time from 37°C to 32°C (mins)
CON 18.5°C N/A 90 ± 1
PB 18.5°C N/A 163 ± 11f
BB 18.5°C N/A 180 ± 57
BB+HP 18.5°C N/A 230 ± 1*bf
CON 0°C 93 ± 4 38 ± 11
PB 0°C 140 ± 1* 75 ± 28
BB 0°C 160 ± 7 68 ± 11cdf
BB+HP 0°C N/A 163 ± 18*f
CON -18.5°C 53 ± 4 30 ± 7
PB -18.5°C 98 ± 18 38 ± 4abc
BB -18.5°C 115 ± 14 68 ± 4c
BB+HP -18.5°C N/A 88 ± 4c
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8.5 Discussion
The aim of the present investigation was to examine field cold protection methods in a non-
shivering casualty model. To simulate real-life rescues these methods were studied over a four-hour
period in a range of environmental temperatures. In support of the hypothesis the Blizzard Heat
survival bag was superior compared to other devices in all environmental temperatures as indicated
by a higher final core temperature. Additionally, the Blizzard Heat survival bag was the only
method that prevented core temperature reaching 24°C, a temperature associated with death (Durrer
et al. 1998). As reported previously, Blizzard survival was superior to polythene (Allen et al, 2010),
yet neither could maintain a core temperature above 24°C during exposure to 0°C. These results
imply that for a non-shivering casualty, lying sedentary and awaiting rescue in a cold environment,
survival time may be increased by the immediate administration of a lightweight active warming
survival device, such as the Blizzard Heat survival bag.
During exposure to 0°C, the hourly reduction in core temperature from the in vitro torso model
protected with a Blizzard Heat survival bag was not only less than the passive devices exposed to
the same conditions, but replicated that of both passive devices in a thermo-neutral environment
(18.5°C). This novel finding supports a previous investigation where an active heating combination
of a multi-layered metalized sheeting survival bag (Blizzard Reflexcell™) with chemical heat pads
was superior to all other methods tested (Allen et al. 2010). Nonetheless, this previous investigation
only exposed fluid models to a thermo-neutral ambient temperature which does not reflect the likely
cold environments experienced by casualties. Exposure to -18.5°C evoked a similar outcome as 0°C
so that the hourly reduction in core temperature from the model protected with a Blizzard Heat
survival bag was again, not only less than both the polythene and Blizzard survival bags in the same
conditions but similar to these passive devices in 0°C. Hourly heat loss was also similar between the
in vitro torso model protected with a Blizzard Heat survival bag in -18.5°C and no protection in
thermo-neutral conditions. These findings have implications for trauma casualties wounded in
125
warmer conditions, who, when air lifted by helicopter will experience ambient temperature drops up
to -15°C per 1000 feet of altitude gain (Johnson et al. 2010). It is likely a Blizzard Heat survival bag
will decrease the risk of accelerated heat loss during altitude gain and as such, reduce trauma related
fatalities.
When exposed to 0°C and 18.5°C, the polythene bag and Reflexcell device without chemical heat
pads (Blizzard survival bag) presented similar hourly heat loss and final core temperatures. This
contradicts a recent investigation where the same multi-layered survival bag was found to be
superior in comparison to single-layer polythene in thermo-neutral conditions (Allen et al. 2010).
Nonetheless, when the fluid model was protected with the Blizzard survival bag, hourly heat loss in
-18.5°C with still air (equivalent to -15°C with 6 km∙h-1
wind speed, -10°C with 20 km∙h-1
wind
speed and -5°C with 95 km∙h-1
wind speed) was less compared with polythene. This also meant the
final core temperature was higher with the Blizzard survival bag which in combination suggests as
ambient temperatures decrease, multi-layered devices are better at reducing heat loss which may
increase survival times and reduce the number of hypothermia related fatalities, particularly when
time to 24°C from 32°C was greater in the Blizzard bag compared to polythene in 0°C and -18.5°C.
However, as aforementioned, when protected with an active device, core temperature did not
decrease to a critical level in any ambient condition.
When the fluid models were exposed to any temperature with no protection, a greater reduction in
core temperature was observed compared to when a protective layer was available. This suggests
for cold casualties unable to shiver, any extra layers that can be provided may indeed reduce the
decline in core temperature (Hamilton and Paton, 1996). Active heating devices such as chemical
heat pads are more beneficial for the immediate field treatment of hypothermic casualties prior to
evacuation to superior methods because of the additional heat energy being put into the system,
particularly when core temperature is critically low (i.e. < 32°C) (Durrer et al. 1998; Allen et al.
2010). Furthermore, of the devices tested in the present study, following the evacuation of
126
casualties from cold to thermo-neutral temperatures (e.g. 18.5°C), an active warming device may
provide the most superior protection for a non-shivering casualty. This is because only a modest
decline in core temperature occurred in 18.5°C during the four hour exposure in comparison to
when fluid models were covered with passive devices.
Regarding surface temperature among all the devices examined, not one met the threshold
temperature considered to cause thermal injury (Moritz and Henriques, 1947) which has also been
shown with human subjects (Appendix J). Similar to previous research (Allen et al. 2010), given
the fluid model in the present study did not consist of a biological organism and had no basal
metabolic activity, extrapolation of this study to efficacy in humans may be limited. Despite this,
the model was effective in detecting drops in temperature among the devices exposed to different
ambient temperatures. Furthermore, the findings of this study reinforce those of a recent
investigation by our group where the multi-layered metallised sheeting with chemical heat pads was
the most superior device (Chapter 6). As such, re-warming of mildly hypothermic cold casualties
to near resting core temperatures occurred with significantly less energy expenditure.
The present study suggests a continuum exists for the amount of heat lost, whereby the lower the
ambient temperature is the greater the difference between heat lost from a passive device is
compared with active heating. Given an increased risk of accidental hypothermia accompanies
previous conclusions in earlier chapters, findings here have implications for those individuals
climbing to high altitudes in cold conditions (Chapter 4 and 5) and those who by accident, have
been immersed in cold water in cold ambient conditions (Chapter 6 and 7). In conclusion, a non-
shivering fluid model exposed to different ambient environments suggested that the effectiveness of
chemical heat pads in combination with a triple layered, metallised survival blanket may counteract
the decline in thermogenesis accompanying the onset of severe hypothermia or administration of
sedatives thus preventing hypothermia related fatalities including those combined with trauma.
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CHAPTER NINE
General Discussion
9.1 Background
Military personnel, athletes and outdoor enthusiasts frequently travel to cold, mountainous regions
for work, training and recreational activities. It is not uncommon therefore, for such individuals to
be exposed to the extreme environmental conditions of cold and cold with hypoxia for prolonged
periods of time. Additionally, arrival at high altitude predominantly occurs prior to hypoxic
acclimatisation. High altitude environments have been suggested to alter thermoregulatory,
metabolic, perceptual (Blatteis and Lutherer, 1976; Johnston et al. 1996; Golja et al. 2004) and
immune responses (Pedersen and Steensberg, 2002) to the cold which may increase the
susceptibility to cold injury (e.g. frostbite, hypothermia) and infection (e.g. URTI). Accidental
hypothermia affects approximately 10% of casualties reported in mountainous environments and is
a significant contributor to fatalities (Moss, 1986; Sharp, 2007). Cold exposure alone is associated
with an increased incidence of bronchorrhea and URTI (Giesbrecht, 1995; Castellani et al. 2002). It
has been suggested that a continuum exists for the effects of body core cooling on immune function
whereby mild decreases in core temperature have little stimulatory effects, but more severe
decreases have depressive effects (Costa et al. 2010). Given the cold and hypoxic environments that
may be encountered during wilderness or mountainous pursuits and the subsequent risks to
thermoregulation and immune function the main objectives of this thesis were to investigate: 1. the
effects of acute and chronic exposure to high altitude on thermoregulation, metabolism (Chapter 4)
and mucosal immune responses (Chapter 5) during cold exposure; 2. the effectiveness of four field
methods for the treatment of cold casualties on thermoregulation and metabolism during an
‘awaiting rescue’ scenario in 0°C following cold water immersion (Chapter 6); 3. the mucosal
immune response to prolonged cold exposure in cold casualties (Chapter 7); and 4. the efficacy of
128
three field protection methods for the treatment of non-shivering cold casualties using an in vitro
torso model exposed to -18.5°C, 0°C and 18.5°C for four hours (Chapter 8).
Findings from the two threads of experiments in this study (i.e. thermoregulation and mucosal
immunity) can be integrated together to help produce a clear representation of potential health risks
for those individuals performing activities in extreme environments including cold and/or hypoxia.
Such findings could be applied and used in practise by a wide spectrum of associations including,
but not limitied to, the medical industry, the military and outdoor pursuits companies. Knowledge
gained from this thesis may help to reduce hypothermic related casulaties in the field and reduce a
potential increased susceptibility to illness and infection from pursuits in these extreme
environments.
9.2 Summary of Main Findings
Un-acclimatised men exposed to hypoxia in the cold demonstrated a reduced capacity for NST via
an increased catabolism of CHO substrates which may have been responsible for the earlier onset
and increased intensity of shivering activity. Nonetheless, hypoxia, regardless of acclimatisation,
did not impair typical core or mean skin temperature responses to the cold. Following an 18 day
high altitude mountaineering expedition, a decrease in shivering despite no changes in core or mean
skin temperature is consistent with a greater reliance on NST. The alterations observed post-
expedition in thermal comfort may suggest greater thermal tolerance but increased susceptibility to
cold injury (Chapter 4). Saliva flow rate was altered during un-acclimatised exposure to hypoxia in
the cold compared with post-expedition, yet α-amylase concentration was increased in the cold with
and without hypoxia in all conditions. However, since s-IgA concentration and secretion rate were
unchanged regardless of hypoxia or cold, it is unlikely reductions in arterial oxygen saturation
negatively effect the mucosal immune response to cold at the level employed in the study (Chapter
5). All four field re-warming methods supported re-warming of shivering cold casualties to near
129
normal resting core temperatures within three hours of cold exposure. Although typical re-warming
parameters were not different between either intervention, metabolic heat production was greater in
polythene bag trials compared with Blizzard during the first hour of cold exposure. Re-warming in
the Blizzard survival bags was achieved with lower TEE which may be beneficial for long term
survival (Chapter 6). While s-IgA concentration was unchanged during and following prolonged
cold stress, saliva flow rate and s-IgA secretion rate were reduced and α-amylase concentration was
increased until the return to normal resting core temperature. This supports that a reduction in core
temperature (≥ 1.5°C) may increase susceptibility to illness and infection (i.e. URTI, influenza)
(Chapter 7). A non-shivering torso model reinforced suggestions that the Blizzard Heat survival
bag was the most superior of the field treatments investigated by demonstrating a reduced amount
of core temperature heat loss and an increase in predicted survival time (Chapter 8).
9.3 Thermoregulation, metabolism and perception
Core and mean skin temperature were unaffected by exposure to hypoxia in the cold regardless of
hypoxic acclimatisation. Similar decrements in core and mean skin temperature were observed
during 2 hours supine rest in SL (FiO2: 20.9%), UN (FiO2: 12.5%) and PEX (FiO2: 12.5%)
conditions (Chapter 4). These results suggest that underlying homeostatic mechanisms are robust
to unaccustomed environmental conditions in order to maintain primary thermoregulation (i.e. core
and skin temperature). Earlier reports are contradictory however, and compared with cold alone, un-
acclimatised exposure to cold and hypoxic environments has been associated with a reduction in
core temperature and an increase in skin temperature (Bullard, 1961; Cipriano and Goldman, 1975;
Kottke et al. 1948). Nonetheless, core temperature has been reported elsewhere as unaltered during
both normobaric and hypobaric hypoxia in the cold (Blatteis and Lutherer, 1976; Brown et al. 1952;
Robinson and Haymes, 1990). A limitation of chapter 4 is that the exposure temperature was 15°C
which may be considered too mild to evoke such a thermoregulatory stress. However, in
130
combination with a simulated high altitude of 4000m it was regarded as an extreme and
unaccustomed climate for the participants taking part. Additionally, this ambient temperature has
been used previously in studies where differences did occur (Cipriano and Goldman, 1975). Given
that the body of evidence surrounding the effect of hypoxia on thermoregulatory responses in the
cold includes a wide spectrum of methodological differences, it would appear that thermoregulatory
alterations cannot be predicted, and therefore suitable precautions, such as following acclimatisation
protocols ahead of travelling, should be taken upon ascent to high altitude.
The metabolic response to cold was impaired during un-acclimatised exposure to hypoxia (Chapter
4). A reduction in heat production coupled with an earlier onset and more intense shivering activity
supports that acute hypoxia suppresses NST (Blatteis and Lutherer, 1976; Bullard, 1961; Gautier,
1996; Robinson and Haymes, 1990). Additionally, significant alterations in lipid and carbohydrate
oxidation were demonstrated prior to acclimatisation. It is plausible to suggest that the hypoxic-
induced suppression of NST by an inhibition of the aerobic catabolism of lipid stores may occur
through an increased hormonal response to hypoxic stress which decreases the lipolytic response of
adipocytes and thus lowers lipid mobilisation (de Glisezinski et al. 1999; Masoro, 1966; Robinson
and Haymes, 1990). As a result, carbohydrate oxidation is increased to fuel intense shivering
thermogenesis (Martineau and Jacobs, 1988). In turn, this may explain how the body maintains core
and mean skin temperature despite the absence of NST in hypoxia (Chaper 4). The severity of
hypoxia-induced metabolic alterations, as a diagnostic marker of homeostatic disruption at altitude,
appears to provide more information regarding the effects of hypoxia during cold exposure
compared to core and mean skin temperature alone. Given that the metabolic response remained
impaired following acclimatisation but shivering activity was reduced, supports that NST recovery
may occur following a high altitude stay (Blatteis and Lutherer, 1976; Mathew et al. 1979). Since
the work in this thesis (Chapter 4) was the first to quantify shivering using electromyography
provides a particularly novel aspect that previous investigations do not.
131
Behavioural thermoregulation is initiated by the perception of thermal comfort (Golja et al. 2004).
In support of a previous report (Golja et al. 2005), acute exposure to a reduced oxygen supply prior
to acclimatisation did not alter sensitivity to the cold. Given core and mean skin temperatures were
similar between trials it is likely the neural information transformed from peripheral sensors giving
rise to the perception of thermal comfort was also similar (Chapter 4). However, following an 18
day altitude expedition the sensation of cold was decreased and thermal comfort was increased
which suggests prolonged hypoxic exposure may impair nerve conduction so that thermal
information is impeded (Golja et al. 2004; Malanda et al. 2008). Consequently, acclimatised
individuals at altitude may often feel warmer than their core temperature would suggest. As a result,
behavioural thermoregulation may be neglected. These alterations observed post-expedition may
suggest a greater thermal tolerance but an increase in susceptibility to cold injury (Chapter 4).
Chapter 6 examined four field re-warming methods for the treatment of cold casualties. Core
temperature re-warming rate was unaffected by the type of re-warming device administered and in
all cases where cold individuals were able to adequately thermoregulate (e.g. shiver) the time taken
to return to normal resting core temperature values was the same. This finding provides further
support to a conclusion of Chapter 4, suggesting that homeostatic mechanisms ensure optimal core
temperature control during exposure to environmental stressors where core temperature is
compromised. Mean weighted skin temperature differed between the field methods however,
whereby the triple-layered metallised sheeting survival bags maintained a higher skin temperature
throughout the cold exposure compared to polythene trials. The administration of hourly hot drinks
(~430 ml) seemed to confer no thermoregulatory advantage compared with polythene survival bags
alone. It is plausible to suggest that these multi-layered devices may reduce the pre-disposition to
peripheral cold injuries (e.g. frostbite) during more prolonged cold exposures (Chapter 6). As a
likely result of the lower mean skin temperature during polythene trials, metabolic heat production
was greater compared with the Blizzard survival bags during the first hour of cold exposure.
132
Furthermore, re-warming in the Blizzard Heat survival bag was achieved with lower TEE which
may be beneficial for long term survival (Tikuisis, 1995; Tikuisis et al. 2002). As hypothesised, a
consequence of the superior protection provided by the Blizzard Heat survival bag improved the
perception of pain and thermal comfort.
That the Blizzard Heat survival bag offered superior thermal protection compared with single layer
polythene (Chapter 6) was also suggested by the results of Chapter 8. An in vitro torso model
exposed to the cold suggested that the Blizzard Heat survival device could maintain a higher core
temperature throughout prolonged exposure to extreme conditions than other methods tested. This
supports previous findings where an active heating combination of a multi-layered metalized
sheeting survival bag (Blizzard Reflexcell™) with chemical heat pads was superior to all other
methods tested (Allen et al. 2010). The findings of Chapter 8 however, offer more information
regarding the depth of thermal protection provided by each device as a result of the number of
different ambient conditions they were exposed to. Consequently, the active heating device was the
only treatment able to prevent core temperature from becoming fatally low in all ambient conditions
when shivering was absent (~24°C; Durrer et al. 1998).This may imply for a non-shivering
casualty, lying sedentary and awaiting rescue in a cold environment, survival time may be increased
by the immediate administration of a lightweight active warming survival device, such as the
Blizzard Heat survival bag. While the results from this in vitro study have obvious limitations, the
model was effective in detecting drops in temperature among the different devices exposed to
different ambient temperatures.
133
9.4 Mucosal Immunity: Saliva flow rate, s-IgA concentration, s-IgA secretion rate, α-
amylase concentration and α-amylase secretion rate
Cold exposure is associated with an increased incidence of bronchorrhea, sinusitis, and URTI
(Clothier, 1974; Giesbrecht, 1995; Castellani et al. 2002; Lavoy et al. 2011). A decrease in s-IgA
has been implicated as a possible causal factor in the increased susceptibility to URTI (Hanson et
al. 1983; Nieman and Nehlsen-Cannarella, 1991; Gleeson et al. 1999; Cairns et al. 2002).
Coincidentally, modest whole body cooling (Trec 35.9°C) via cold air exposure (0°C) has
demonstrated a decrease in s-IgA responses (Costa et al. 2010), nevertheless literature surrounding
the effects of hypoxia on saliva responses are limited (Meehan et al. 1988; Muchmore et al. 1981).
Further, whether the combination of hypoxia and cold exacerbates alterations in mucosal immunity,
until now has not been examined.
Contradictory to the hypotheses in Chapter 5, hypoxia did not alter typical mucosal immune
responses in the cold. However, following cold water immersion to reduce core temperature to
36°C in a normoxic environment, s-IgA secretion rate was reduced and α-amylase concentration
was increased (Chapter 7). This suggests that when cold stress is mild (15°C) and core temperature
remains un-compromised, hypoxia unlikely increases the predisposition to URTI. Nonetheless,
given that s-IgA secretion rate was altered following a more severe cold stress in normoxia
(Chapter 7), it is not unreasonable to suggest that colder conditions in hypoxia may indeed evoke
s-IgA alterations, particularly as saliva flow rate was mildly suppressed in hypoxia in combination
with a cold induced increase in α-amylase concentration (Chapter 5). Although physiological
mechanisms underlying mucosal alterations remain unclear, it is likely that both neural and
endocrine factors influence such responses (Pedersen and Steensberg, 2002). As arterial oxygen
saturation was reduced during un-acclimatised hypoxic exposure in Chapter 5, both the neural and
endocrine systems may have been compensating to maintain homeostasis (Mazzeo, 2005), thus
explaining the difference in saliva flow rate. Nonetheless, the absence of hypoxia-induced s-IgA
134
alterations to cold suggests the mucosal immune system may be robust to a combination of
environmental stressors and as such common URTI complaints may not resonate upon arrival to
high altitude.
Following a prolonged stay at altitude, saliva flow rate, α-amylase and s-IgA responses remained
unaltered during hypoxic exposure in the cold. This may be as a result of the observed recovery in
arterial oxygen saturation to near normal sea level values following the 18 day expedition. Given an
altitude of 3500m has been suggested to correspond to the threshold at which the physiological
changes intended to tolerate the drop in partial pressure of oxygen fail to fully compensate the effect
of hypoxia (Colin et al. 1999), it has been speculated that at or above this altitude the adverse effect
of hypoxia on s-IgA is more substantial (Tiollier et al. 2005). However, in Chapter 5, both un-
acclimatised and acclimatised participants exposed to a simulated altitude of 4000m while at rest
displayed no alterations in s-IgA. Therefore, it is more likely the previously observed s-IgA changes
(Tiollier et al. 2005) were not due to the level of hypoxia per se or as a result of chronic exposure
but more likely a cumulative effect of intense physical training. Additionally, the normobaric nature
of the altitude exposure during Chapter 5 and other work (Tiollier et al. 2005) does not suitably
replicate typical high altitude conditions. If barometric pressure was manipulated to reflect the value
coinciding with that level of altitude (i.e. 661mmHg at 4000m) the impact on homeostasis and
subsequent mucosal immune status may be greater during cold exposure. On the contrary, since s-
IgA concentration and secretion rate were unchanged in both altitude exposures compared to
normoxia (Chapter 5) suggests it is unlikely that altitude exposure while at rest, before and
following an altitude stay, causes disruption to either sympathetic nervous system activity (Mazzeo
et al. 2003) or alpha-adrenergic mechanisms (Ring et al. 2000). In conclusion, exposure of
lowlanders to normobaric hypoxia, whether acute or following a prolonged stay, does not evoke a
physiological or metabolic stress great enough to disrupt the typical mucosal immune response to
cold. Very little resesrch exists with regard to mucosal immunity at altitude so while the experiment
135
here (Chapter 5) does not offer masses of information it does provide the beginnings of what
should be an area of continual investigation.
Chapter 7 identifies that saliva flow rate and s-IgA secretion rate are reduced and α-amylase
concentration increased in mildly hypothermic, sedentary individuals exposed to the cold. These
findings are consistent with previous work (Costa et al. 2010), yet the results of Chapter 7 are
strengthened by the inclusion of a thermo-neutral control trial to account for the diurnal variations
in saliva parameters. However, that cold exposure and mild hypothermia reduce s-IgA secretion rate
should be suggested with caution. This is because s-IgA secretion rate at baseline, prior to cold
exposure, was also lower than at that same time during thermo-neutral control. While psychological
stress has been found to reduce s-IgA concentration in humans (Stone et al.1987; Stone et al. 1994;
Cohen et al. 2001), it is possible that participants were more anxious on the morning of their cold
trial and as a result s-IgA responses were already altered. In the future, blinding participants to the
trial may avoid this potential anticipatory effect. Nonetheless, following re-warming, s-IgA
secretion rate was greater and α-amylase concentration lower than when participants displayed their
lowest core temperature, whereas no significant changes occurred throughout the thermo-neutral
control trial. This suggests that until re-warming is initiated, cold, sedentary individuals are at risk
from increased mucosal immune disturbance which supports the popular belief that most common
colds occur because the host is exposed to a cold environment (Dowling et al. 1958; Biggar et al.
1984). Furthermore, Chapter 7 provides some evidence that there may be a direct causal relation
between an individual getting cold and subsequently developing an infection (Lavoy et al. 2011).
To confirm this however, studies including larger subject numbers would be beneficial. In
conclusion, a reduction in core temperature (≥ 1.5°C) resulting from cold water immersion and
subsequent cold air exposure suppresses the usual daily s-IgA response which may increase
susceptibility to illness and infection (i.e. URTI, common colds, influenza) if re-warming is not
initiated immediately.
136
9.5 Future directions
Work in this area could continue to develop firstly by repeating the experiments outlined in this
thesis in order to gain larger sample sizes and thus, more specific conclusions. Secondly, methods
for each experiment could be performed in conditions that pose a greater strain on the human body
(e.g. colder and more hypoxic) to demonstrate particular thresholds for normal human body
function. It would be beneficial to examine a wider variety of immune parameters in order to
provide a more complete template of the likely effects of exposure to extreme environments.
137
9.6 Conclusions
The major conclusions from this thesis are:
I. Demonstrated by a reduced capacity for NST via an increased catabolism of CHO, exposure
to hypoxia in the cold impairs the thermoregulatory and metabolic response of un-
acclimatised men.
II. Exposure to a simulated high altitude of 4000m in the cold following an 18 day
mountaineering expedition evokes a decrease in shivering activity despite no changes in
core or mean skin temperature which likely represents a greater reliance on NST for heat
production.
III. Alterations observed post-expedition in thermal comfort during exposure to a simulated high
altitude of 4000m in the cold may suggest a greater perception of thermal tolerance but an
increase in susceptibility to cold injury.
IV. Two hours of exposure to a simulated high altitude of 4000m does not disrupt the typical
mucosal immune response to cold regardless of hypoxic acclimatisation status. Common
URS are not likely to be increased upon arrival to high altitude or following a prolonged
stay.
138
V. Of four cold treatment methods tested in 0°C, with minimal wind, all were able to assist
shivering cold casualties to increase core temperature to normothermia within three hours.
VI. Blizzard survival bags are a more efficient field re-warming device than polythene bags
given complete core re-warming was achieved with lower total energy expenditure which
may be beneficial for long term survival.
VII. A reduction in core temperature (≥ 1.5°C) resulting from cold water immersion and
subsequent cold air exposure alters the usual daily mucosal immune responses which may
increase susceptibility to illness and infection (i.e. URTI, common colds, influenza) if re-
warming is not initiated immediately.
VIII. In Vitro torso models protected in various ambient temperatures with different cold
protection field treatments highlighted that the Blizzard Heat survival bag was superior at
reducing heat loss which resulted with higher final core temperatures compared to other
devices. This active heating device was the only treatment able to prevent core temperature
from becoming fatally low in all ambient conditions when shivering was absent
IX. The effectiveness of chemical heat pads in combination with a triple layered, metallised
survival blanket may prevent the decline in thermogenesis accompanying the onset of severe
hypothermia or administration of sedatives, thus preventing hypothermia related fatalities in
the field, including those combined with trauma.
139
References
Abramson DI. (1967). Circulation of the extremities. Academic, New York. 116 – 119.
Adams T and Heberling EJ. (1958). Human physiological responses to a standardized cold stress as
modified by physical fitness. Journal of Applied Physiology. 13: 226 - 230.
Ainslie PN, Reilly T. (2003). Physiology of accidental hypothermia in the mountains: a forgotten
story. British Journal of Sports Medicine. 37: 548 – 550.
Allen PB, Salyer SW, Dubick MA, Holcomb JB, Blackbourne LH. (2010) Preventing hypothermia:
Comparison of current devices used by the U.S. Army with an in vitro warmed fluid model. The
Journal of Trauma. 69: 154 – 161.
Armstrong LE, Maresh CM, Castellani JW, Bergeron MF, Kenefick RW, Lagasse KE, Riebe D.
(1994). Urinary indices of hydration status. International Journal of Sport Nutrition. 4: 265 – 279.
Armstrong LE. (2000). Performing in extreme environments. Human Kinetics, Champaign, Il.
Arthurs Z, Cuadrado D, Beekley A, Grathwohl K, Perkins J, Rush R, Sebesta J. (2006). The impact
of hypothermia on trauma care at the 31st combat support hospital. American Journal of Surgery.
191(5): 610 – 614.
Ashes MI. (1999). Infections of the upper respiratory tract. In Taussig LM, Landau LI, eds.
Pediatric Respiratory Medicine. Mosby Inc Missouri. 530 - 547.
Astrup A, Bulow J, Madsen J, Christensen NJ. (1985). Contribution of BAT and skeletal muscle to
thermogenesis induced by ephedrine in man. American Journal of Physiology. 248: E507 - E515.
Aw D, Silva AB, Palmer DB. (2007). Immunosenescence: emerging challenges for an ageing
population. Immunology. 120: 435 – 46.
140
Baetjer A. (1967). Effect of ambient temperature and vapour pressure on cilia-mucus clearance rate.
Applied Journal of Physiology. 23: 498 – 504.
Bailey DM, Davies B, Castell LM, Collier DJ, Milledge JS, Hullin DA, Seddon PS, Young IS.
(2003). Symptoms of infection and acute mountain sickness; associated metabolic sequelae and
problems in differential diagnosis. High Altitude Medicine and Biology. 4: 319 – 331.
Bangs CC. (1984). Hypothermia and frostbite. Emergency Medicine Clinics of North America. 2(3):
475 – 487.
Bay J, Nunn JF, Prys-Roberts C. (1968). Factors influencing arterial PO2 during recovery from
anaesthesia. British Journal of Anaesthesia. 40: 398 - 407.
Bazett HC, Love L, Newton M, Eisenberg L, Day R, Forster R. (1948). Temperature changes in
blood flowing in arteries and veins in man. Journal of Applied Physiology. 1: 3 – 19.
Beaton JR. (1963). Metabolic effects of dietary protein level with caloric restriction in cold exposed
rats. Canadian Journal of Biochemistry and Physiology. 41: 151 – 160.
Beilen B, Shavit Y, Razumovsky J, Wolloch Y, Zeidel A, Bessler H. (1998). Effects of mild
perioperative hypothermia on cellular immune responses. Anesthesiology. 89: 1133 – 1140.
Beilman GJ, Blondet JJ, Nelson TR, Nathens AB, Moore FA, Rhee P, Puyana JC, Moore EE, Cohn
SM. (2009). Early Hypothermia in Severely Injured Trauma Patients Is a Significant Risk Factor for
Multiple Organ Dysfunction Syndrome but Not Mortality. Annals of Surgery. 249(5): 845 – 850.
Bennet J, Ramachandra V, Webster J, Carli F. (1994). Prevention of hypothermia during hip
surgery: effect of passive compared with active skin surface warming. British Journal of
Anaesthesia. 73: 180 – 183.
141
Berglund B, and Hemmingsson P. (1990). Infectious disease in elite cross-country skiers: a one year
incidence study. Clinical Sports Medicine. 2: 19 – 23.
Bernard SA, Gray TW, Buist MD, Jones BM, Silvester W, Gutteridge G, Smith K.
(2002).Treatment of comatose survivors of out of hospital cardiac arrest with induced hypothermia.
New England Journal of Medicine. 346: 557 – 563.
Biem J, Koehncke N, Classen D, Dosman J. (2003). Out of the cold: management of hypothermia
and frostbite. Canadian Medical Association Journal. 168: 305 – 311.
Biesel WR, Goldman RF, Joy RJT. (1968). Metabolic balance studies during induced hypothermia
in man. Journal of Applied Physiology. 24: 1 – 10.
Biggar WD, Bohn DJ, Kent G, Barker C, Hamilton G. (1984). Neutrophil migration in vitro and in
vivo during hypothermia. Infection and Immunity. 857 – 859.
Bishop NC, Blannin AK, Armstrong E, Rickman M, Gleeson M. (2000). Carbohydrate and fluid
intake affect the saliva flow rate and IgA response to cycling. Medicine and Science in Sports and
Exercise. 32: 2046 – 2051.
Bishop NC. (2006). Acute exercise and acquired immune function. In: Gleeson M (ed) Immune
function in sport and exercise. Churchill Livingstone. Elsevier. 91 – 113.
Bittel JHM. (1987). Heat debt as an index of cold adaptation in men. Journal of Applied
Physiology.62(4): 1627 – 1634.
Bittel JHM, Nonotte-Varly C, Livecchi-Gonnot GH, Savourey GLMJ, Hanniquet AM. (1988).
Physical fitness and thermoregulatory reactions in a cold environment in men. Journal of Applied
Physiology. 65(5): 1984 – 1989.
142
Bittel JHM, Livecchigonnot GH, Hanniquet AM, Poulain C, Etienne JL. (1989). Thermal-changes
observed before and after JL Etienne’s journey to the North Pole. Is central nervous system
temperature preserved in hypothermia? European Journal of Applied Physiology and Occupational
Physiology. 58: 646 – 651.
Blatteis CM, Lutherer LO. (1976). Effect of altitude exposure on thermoregulatory response of man
to cold. Journal of Applied Physiology. 41(6): 848 – 858.
Borg G, Borg E. (2001). A new generation of scaling methods: level anchored ratio scaling.
Psychologica. 28: 15 – 45.
Bosch JA, Brand HK, Ligtenberg TJM, Bermond B, Hoogstraten J, Amerongen AV. (1996).
Psychological stress as a determinant of protein levels and salivary induced aggregation of
Streptococcus gordonii in human whole saliva. Psychological Medicine. 58: 374 – 382.
Bosch JA, Ring C, de Geus EJ, Veerman EC, Amerongen AV. (2002). Stress and secretory
immunity. International Review of Neurobiology. 52: 213 – 253.
Bourke DL, Wurm H, Rosenberg M, Russel J. (1984). Intraoperative heat conservation using a
reflective blanket. Anesthesiology. 60: 151 – 154.
Boutelier C, Livingstone SD, Bougues L, Reed LD. (1982). Thermoregulatory changes to cold in
pre-acclimated and non-acclimated men following an arctic winter stay. In: Radomski M, Boutelier
C, Buguet A (eds). Koll Stool II. University of Toronto Press, Toronto. 1 – 19.
Bracker MD. (1992). Environmental and thermal injury. Clinical Sports Medicine. 11: 419 – 436.
Brandtzaeg P, Baekkevold ES, Farstad IN, Jahnsen FL, Johansen FE, Nilsen EM, Yamanaka T.
(1999). Regional specialisation in the mucosal immune system: What happens in the
microcompartments? Immunology Today. 20: 141 – 151.
143
Brenner IK, Castellani JW, Gabaree C, Young AJ, Zamecnik J, Shephard RJ, Shek PN. (1999).
Immune changes in humans during cold exposure: effects of prior heating and exercise. Journal of
Applied Physiology. 87: 699 – 710.
Broman M, Kallskog O, Nygren K, Wolgast M. (1998). The role of anti-diuretic hormone in cold
induced diuresis in the anaesthetised rat. Acta Physiologica Scandinavia. 162: 475 – 480.
Brown AL, Vawter GF, Marbarger JP. (1952). Temperature changes in human subjects during
exposure to lowered oxygen tension in a cool environment. Journal of Aviation Medicine. 23: 456.
Buggy D, Hughes N. (1994). Pre-emptive use of the space blanket reduces shivering after general
anaesthesia. British Journal of Anaesthesia. 72: 393-396.
Buggy DJ, Crossley AWA. (2000). Thermoregulation, mild perioperative hypothermia and post
anaesthetic shivering. British Journal of Anaesthesia. 84(5): 615 – 628.
Bullard RW. (1961). Effect of hypoxia on shivering in man. Aerospace medicine. 32: 1143 – 1147.
Burton AC. (1935). Human calorimetry. II. The average temperature of the tissues of the body.
Journal of Nutrition. 9: 264 – 280.
Burton AC, Edholm OG. (1955). Man in a cold environment. London. Arnold.
Burton AC, Snyder KA, Leach WG. (1955). Damp cold vs. dry cold: special effects of humidity on
heat exchange of unclothed man. Journal of Applied Physiology. 8: 269 - 278.
Buskirk ER, Thompson RH, Whedon GD. (1963). Metabolic response to cold air in men and
women in relation to total body fat content. Journal of Applied Physiology. 18: 603 - 612.
Cabanic M, Ramel P, Duclaux R, Joli M. (1969). Indifference to pain and thermic comfort (two
cases). Presse Medicine. 77: 2053 – 2054.
144
Cairns J, Booth C. (2002). Salivary immunoglobulin-A as a marker of stress during strenuous
physical training. Aviation, Space and Environmental Medicine. 73: 1203 – 1207.
Calbet JA. (2003). Chronic hypoxia increases blood pressure and noradrenaline spillover in healthy
humans. Journal of Physiology. 551: 379 – 386.
Cappaert TA, Stone JA, Castellani JW, Krause BA, Smith D, Stephens BA. (2008). National
Athletic Trainers' Association Position Statement: Environmental Cold Injuries. Journal of Athletic
Training. 43(6): 640 – 658.
Casa DJ, Clarkson PM , Roberts WO. (2005). American College of Sports Medicine roundtable on
hydration and physical activity: consensus statements. Current Sports Medicine Reports. 115 – 127.
Castellani JW, Young AJ, Sawka MN, Pandolf KB. (1998). Human thermoregulatory responses
during serial cold-water immersions. Journal of Applied Physiology. 85: 204 – 209.
Castellani JW, Young AJ, Kain JE, Rouse A, Sawka MN. (1999). Thermoregulation during cold
exposure: effects of prior exercise. Journal of Applied Physiology. 87: 247 – 252.
Castellani JW, Young AJ, Degroot DW, Stulz DA, Cadarette BS, Rhind SG, Zamecnik J, Shek PN,
Sawka MN. (2001). Thermoregulation during cold exposure after several days of exhaustive
exercise. Journal of Applied Physiology. 90: 939 – 946.
Castellani JW, Brenner IKM, Rhind SG. (2002). Cold exposure: human immune responses and
intracellular cytokine expression. Medicine and Science in Sport and Exercise. 34: 2013 – 2020.
Chard T. (1990). An introduction to radioimmunoassay and related techniques (4th
ed.).
Amsterdam: Elsevier.
Chatterton RT, Vogelsong KM Jr, Lu YC, Ellman AB, Hudgens GA. (1996). Salivary alpha-
amylase as a measure of endogenous adrenergic activity. Clinical physiology. 16: 433 – 48.
145
Chen ACN, Rappelsberger P, Filz O. (1998). Topology of EEG coherence changes may reflect
differential neural network activation in cold and pain perception. Brain Topography. 11: 125 –
132.
Chicharro JL, Lucia A, Perez M, Vaquero AF, Urena R. (1998). Saliva composition and exercise.
Sports Medicine. 26: 17 – 27.
Chohan IS, Sing I, Balakrishnan K, Talwar GP. (1975). Immune responses in human subjects at
high altitude. International Journal of Biometeorology. 19: 137 – 143.
Ciofolo M, Clergue F, Devilliers C, Ben Aramar M, Viars P. (1989). Changes in ventilation,
oxygen uptake, and carbon dioxide output during recovery from isoflurane anesthesia.
Anesthestology. 70: 737 - 741.
Cipriano LF, Goldman RF. (1975). Thermal responses of unclothed men exposed to both cold
temperatures and high altitudes. Journal of Applied Physiology. 39(5): 796 - 800.
Clothier JG. (1974). Medical aspects of work in arctic areas. Practitioner. 213: 805 – 811.
Cogoli A. (1981). Hematological and immunological changes during space flight. Acta
Astronautica. 8: 995 – 1002.
Cohen, J. (1988) Statistical power analysis for behavioural sciences. Hillsdale, NJ: Lawrence
Erlbaum Associates.
Cohen S, Miller GE, Rabin BS. (2001). Psychological stress and antibody response to
immunization: A critical review of the human literature. Psychosomatic Medicine. 63: 7 – 18.
146
Cohen S. (2005). Keynote presentation at the Eight International Congress of Behavioral Medicine:
the Pittsburgh common cold studies: psychosocial predictors of susceptibility to respiratory
infectious illness. International Journal of Behavioral Medicine.12: 123 – 131.
Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. (2009). Sleep habits and
susceptibility to the common cold. Archives of Internal Medicine. 169: 62 – 67.
Cole AS, Eastoe JE. (1988). Biochemistry and Oral Biology. London: Wright. 476 – 477.
Colin J, Timbal J, Houdas Y, Boutelier C, Guieu JD. (1971). Computation of mean body
temperature from rectal and skin temperatures. Journal of Applied Physiology. 31: 484 – 489.
Colin J, Marotte H, Crance JP. (1999). L’hypoxie d’altitude. In: Colin J, Timbal J (eds). Medecine
Aerospatiale expansion. Scientifique Publications. Paris. 55 – 74.
Collis ML. (1976). Treatment of the hypothermic subject. In: Greene B (ed) Cold Water
Symposium. Toronto. Royal Life Saving Society of Canada. 31 – 32.
Collis ML, Steinman AM, Chaney RD. (1977). Accidental hypothermia: an experimental study of
practical rewarming methods. Aviation, Space and Environmental medicine. 48: 625 – 632.
Conway GA, Husberg BJ & Lincoln JM (1998) Cold as a risk factor in working life in the
circumpolar regions. In: Holmér I & Kuklane K (eds) Problems with cold work. Arbete och hälsa
18: 1 - 10. National Institute for Working Life, Solna.
Costa RJS, Harper-Smith A, Oliver SJ, Walters R, Maassen N, Bilzon JLJ, Walsh NP. (2010). The
effects of two nights of sleep deprivation with or without energy restriction on immune indices at
rest and in response to cold exposure. European Journal of Applied Physiology. 109: 417 – 428.
147
Coyle EF. (1995). Substrate utilization during exercise in active people. The American Journal of
Clinical Nutrition. 61: 968 – 979.
Crockett KV, (1995). Scottish Mountain Activities. The Scottish Mountaineering Club Journal,
Aberdeen, UK: Review Publications: 507-534.
Cruz AA, Naclerio RM, Proud D, Togias A. (2006). Epithelial shedding is associated with reactions
to cold, dry air. Journal of Allergy and Clinical Immunology. 117: 1351 – 1358.
Cunningham JJ. (1980). A reanalysis of the factors influencing basal metabolic rate in normal
adults. American Journal of Clinical Nutrition. 33: 2372 – 2374.
Cypress AM, Lehman S, Williams G, Tal I, Rodman D, Goldfine AB, Kuo FC, Palmer EL, Tseng
Y, Doria A, Kolodny GM, Kahn RC. (2009). Identification and importance of brown adipose tissue
in adult humans. The New England Journal of Medicine. 360: 1509 – 1517.
Daanen HAM, Van De Linde FJG. (1992). Comparison of four non-invasive rewarming methods
for mild hypothermia. Aviation, Space and Environmental Medicine. 63: 1070 – 1076.
Daanen HAM, Van de Linde FJG, Romet TT, Ducharme MB. (1997). The effect of body
temperature on the hunting response of the middle finger skin temperature. European Journal of
Applied Physiology. 76: 538 – 543.
Daanen HAM, van Ruiten HJA. (2000). Cold-Induced Peripheral Vasodilation at High Altitudes -
A Field Study. High altitude medicine and biology. 1: 323 – 329.
Daanen HAM. (2003). Finger cold-induced vasodilation: a review. European Journal of Applied
Physiology. 89: 411 – 426.
Danzl DF, Pozos RS. (1994). Accidental hypothermia. New England Journal of Medicine. 331:
1757.
148
Danzl DF. (2001). Accidental hypothermia. In: Auerbach P, ed. Wilderness Medicine. 4th edition.
Mosby. 51 – 103.
Diaz J, Garcia R, Lopez C, Linares C, Tobias A, Prieto L. (2005). Mortality impact of extreme
winter temperatures. International Journal of Biometeorology. 49: 179 – 183.
Diesel D, Lebel J, Tucker A. (1991). Pulmonary particle deposition and airway mucociliary
clearance in cold-exposed calves. American Journal of Veterinary Research. 52: 1665 – 1671.
Dill DB, Costill DL. (1974). Calculation of percentage changes in volumes of blood, plasma, and
red cells in dehydration. Journal of Applied Physiology. 37. 247 – 248.
Dowd FJ. (1999). Saliva and dental caries. Dental Clinics of North America. 43: 579 - 597.
Dowling HF, Jackson GG, Spiesman IG, Inouye T. (1958). Transmission of the common cold to
volunteers under controlled conditions. American Journal of Hygiene. 68: 59 – 65.
Du Bois D, Du Bois EF. (1916). Clinical calorimetry. Tenth paper: a formula to estimate the
approximate area if height and weight be known. Archives of Internal Medicine. 17: 863 – 871.
Ducharme MB, Vanhelder WP, Radomski W. (1991). Cyclic intramuscular temperature fluctuations
in the human forearm during cold-water immersion. European Journal of Applied Physiology. 63:
188 – 193.
Ducharme MB, Tikuisis P, Potter P. (2004). Selection of military survival gears using thermal
manikin and computer survival model data. Journal of Applied Physiology. 92: 658 – 662.
Durrer B, Brugger H, Syme D. (1998). The medical on site treatment of hypothermia. Sion,
Switzerland: Commission For Mountain Emergency Medicine.
149
Eastridge BJ, Owsley J, Sebesta J, Beekly A, Wade C, Wildzunas R, Rhee P, Holcomb J. (2006).
Admission physiology criteria after injury on the battlefield predict medical resource utilisation and
patient mortality. Journal of Trauma. 61(4): 820 – 823.
Eccles R. (2002). An explanation for the seasonality of acute upper respiratory tract viral infections.
Acta Otolaryngology. 122: 183 – 191.
Eiseman B, Moore EE, Meldrum DR, Raeburn C. (2000). Feasibility of damage control surgery in
the management of military combat casualties. Archives of Surgery. 135(11): 1323 – 1327.
Eyolfson DA, Tikuisis P, Xu X, Weseen G, Giesbrecht GG. (2001). Measurement and prediction of
peak shivering intensity in humans. European Journal of Applied Physiology. 84: 100 – 106.
Farkash U, Lynn M, Scope A, Maor R, Turchin N, Sverdlik B, Eldad A. (2002). Does pre-hospital
fluid administration impact core body temperature and coagulation functions in combat casualties?
Injury: International Journal of the Care of the Injured. 33: 103 – 110.
Felicijan A, Golja P, Milcinski M, Cheung SS, Mekjavic IB. (2008). Enhancment of cold induced
vasodilation following acclimatization to altitude. European Journal of Applied Physiology. 104:
201 – 206.
Fendrick AM, Monto AS, Nightingale B, Sarnes M. (2003). The economic burden of non-infl
uenza-related viral respiratory tract infection in the United States. Archives of Internal Medicine.
163: 487 – 494.
Fiala D, Lomas KJ, Stohrer M. (2001). Computer prediction of human thermoregulatory and
temperature responses to a wide range of environmental conditions. International Journal of
Biometeorology. 45: 143 – 159.
150
Folk GE. (1974). Textbook of Environmental Physiology. Lea and Fibiger. Philadelphia, PA. 98 –
215.
Forstot RM. (1995). The etiology and management of inadvertent perioperative hypothermia.
Journal of Clinical Anesthesia. 7: 657 – 674.
Francis JL, Gleeson M, Lugg DL, Clancy RL, Ayton JM, Donovan K, McConnell CA, Tingate TR.
Thorpe B, Watson A. (2002). Trends in mucosal immunity in Antarctica during six Australian
winter expeditions. Immunology and Cell Biology. 80: 382 – 390.
Frank SM, El-Gamal N, Raja SN, Wu PK. (1996). Alpha-adrenoreceptor mechanisms of
thermoregulation during cold challenge in humans. Clinical Science. 91: 627 – 631.
Frank SM, Higgins MS, Fleisher LA, Sitzman JV, Raff H, Breslow MJ. (1997). Adrenergic,
respiratory and cardiovascular effects of core cooling in humans. American Journal of Physiology.
272: 557 – 562.
Freeman J, Pugh LGCE. (1969). Hypothermia in mountain accidents. International Anaesthesiology
Clinic. 7: 997 - 1007.
Gagge AP, Gonzalez RR. (1996). Mechanisms of heat exchange: biophysics and physiology. In
Fregly MJ, Blatteis CM (eds). Handbook of Physiology, Section 4, Environmental Physiology.
Oxford University Press, New York. 45 – 85.
Ganz T, Selsted ME, Szklarek D, Harwig SS, Daher K, Bainton DF, Lehrer RI. (1985). Defensins.
Natural peptide antibiotics of human neutrophils. Journal of Clinical Investigation. 76: 1427 –
1435.
Ganz T. (2003). Defensins: Antimicrobial peptides of innate immunity. Nature Reviews:
Immunology. 3: 710 – 720.
151
Giesbrecht GG, Bristow GK, Uin A, Ready AE, Jones RA. (1987). Effectiveness of three field
treatments for induced mild (33°C) hypothermia. Journal of Applied Physiology. 63: 2375 – 2379.
Giesbrecht GG, Bristow GK. (1992). A second postcooling afterdrop: more evidence for a
convective mechanism. Journal of Applied Physiology. 73(4): 1253 – 1258.
Giesbrecht GG, Schroeder M, Bristow GK. (1994). Treatment of mild immersion hypothermia by
forced air warming. Aviation, Space and Environmental Medicine. 65: 803 – 808.
Giesbrecht GG, Sessler DI, Mekjavic IB, Schroeder M, Bristow GK. (1994). Treatment of mild
immersion hypothermia by direct body-to-body contact. Journal of Applied Physiology. 76: 2373 –
2379.
Giesbrecht GG. (1995). The respiratory system in a cold environment. Aviation, Space and
Environmental Medicine. 66: 890 – 902.
Giesbrecht GG, Bristow GK. (1997). Recent advances in hypothermia research. Annals of the New
York Academy of Sciences. 813: 663 – 675.
Giesbrecht GG, Goheen MSL, Johnston CE, Kenny GP, Bristow GK, Hayward JS. (1997).
Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in
hypothermic humans. Journal of Applied Physiology. 83(5): 1630 – 1634.
Giesbrecht GG. (2000). Cold stress, near drowning and accidental hypothermia: a review. Aviation,
Space and Environmental Medicine. 71: 733 – 752.
Giesbrecht GG. (2001). Emergency treatment of hypothermia. Emergency Medicine. 13: 9 – 16.
Giesbrecht GG. (2001). Prehospital treatment of hypothermia. Wilderness and Environmental
Medicine. 12(1): 24 - 31.
152
Gleeson M, Bishop NC. (1999). Immunology. In: Maughan RJ (ed.). Basic and Applied Sciences
for Sports Medicine. Oxford: Butterworth Heinemann: 199 – 236.
Gleeson M, McDonald WA, Pyne DB, Cripps AW, Francis JL, Fricker PA, Clancy RL. (1999).
Salivary IgA levels and infection risk in elite swimmers. Medicine and Science in Sports and
Exercise. 31: 67 – 73.
Gleeson M. (2000). Mucosal immunity and respiratory illness in elite athletes. International
Journal of Sports Medicine. 21(1): 33 – 43.
Gleeson M, Francis JL, Lugg DJ, Clancy RL, Ayton JM, Reynolds JA, McConnell CA. (2000). One
year in Antarctica: Mucosal immunity at three Australian stations. Immunology and Cell Biology.
78: 616 – 622.
Gleeson M, Pyne DB. (2000). Exercise effects on mucosal immunity. Immunology and Cell
Biology. 78: 536 – 544.
Gleeson M, Bishop NC, Sterne VL, Hawkins AJ. (2001). Diurnal variation in saliva
immunoglobulin A concentration and the effect of a previous day of heavy exercise. Medicine and
Science in Sports and Exercise. 33: supplement, ISEI abstract 54.
Glickman-Weiss EL. Nelson AG, Hearon CM, Vasanthakumar SR, Stringer BT. (1993). Does
feeding regime affect physiological and thermal responses during exposure to 8, 20, and 27°C?
European Journal of Applied Physiology. 67: 30 – 34.
Glickman-Weiss EL. Nelson AG, Hearon CM, Windhauser M, Heltz D. (1994). The thermogenic
effect of carbohydrate feeding during exposure to 8, 12, and 27°C? European Journal of Applied
Physiology. 68: 291 – 297.
153
Goheen MSL, Ducharme MB, Kenny GP, Johnston CE, Frim J, Bristow GK, Giesbrecht GG.
(1997). Efficacy of forced-air and inhalation rewarming by using a human model for severe
hypothermia. Journal of Applied Physiology. 83(5): 1635 – 1640.
Golden FSC. (1973). Recognition and treatment of immersion hypothermia. Proceedings of the
Royal Society of Medicine. 66: 1058 – 1061.
Golden FSC, Hervey GR. (1977). Themechanism of the after-srop following immersion
hypothermia in pigs. Journal of Physiology London. 272: 26 – 27.
Golden FSC, Tipton MJ, Scott RC. (1997). Immersion, near-drowning and drowning. British
Journal of Anaesthesia. 79: 1- 2.
Golja P, Kacin A, Tipton MJ, Eiken O, Mekjavic IB. (2004). Hypoxia increases the cutaneous
threshold for the sensation of cold. European Journal of Applied Physiology. 92: 62 – 68.
Golja P, Kacin A, Tipton MJ, Mekjavic IB. (2005). Moderate hypoxia does not affect the zome of
thermal comfort. European Journal of Applied Physiology. 93: 708 – 713.
Goodenough RD, Royle GT, Nadel ER, Wolfe MH, Wolfe RR. (1982). Leucine and urea
metabolism in acute human cold exposure. Journal of Applied Physiology: Respiratory,
Environmental and Exercise Physiology. 53(2) 367 – 32.
Grandjean AC, Reimers KJ, Bannick KE, Haven MC. (2000). The effect of caffeinated, non
caffeinated, caloric and non-caloric beverages on hydration. Journal of the American College of
Nutrition. 19: 591 – 600.
Grant SJ, Dowsett D, Hutchison C, Newell J, Connor T, Grant P, Watt M. (2002). A comparison of
mountain rescue casualty bags in a cold, windy environment. Wilderness and Environmental
Medicine. 13: 36 - 44.
154
Griefahn B, Mehniert P, Brode P, Forsthoff A. (1995). Health Hazards and Work in Moderate Cold.
Proc. Of International Symposium: From Research and Prevention - Managing Occupational and
Environmental Health Hazards. Finnish Institute of Occupational Health, Helsinki.
Grissom CK, Radwin MI, Scholand MB, Harmston CH, Muetterties MC, Bywater TJ. (2004).
Hypercapnia increases core temperature cooling rate during snow burial. Journal of Applied
Physiology. 96: 1365 – 1370.
Grissom CK, McAlpine JC, Harmston CH, Radwin MI, Giesbrecht GG, Scholand MB, Morgan JS.
(2008). Hypercapnia effect on core cooling and shivering threshold during snow burial. Aviation,
Space and Environmental Medicine. 79: 735 – 742.
Grissom CK, Harmston CH, McAlpine JC, Radwin MI, Ellington B, Hirshberg EL, Crouch A.
(2010). Spontaneous endogenous core temperature rewarming after cooling due to snow burial.
Wilderness and Environmental Medicine. 21: 229 – 235.
Group THACAS. (2002). Mild therapeutic hypothermia to improve the neurological outcome after
cardiac arrest. New England Journal of Medicine. 346: 549 – 556.
Guyton AC. (1996). Body temperature, temperature regulation and fever. In: Guyton AC, Hall JE,
eds. Textbook of Medical Phsiology, 9th
edition. Philadelphia: WB Saunders. 911 – 922.
Hajat S, Bird W, Haines A. (2004). Cold weather and GP consultations for respiratory conditions by
elderly people in 16 locations in the UK. European Journal of Epidemiology. 19: 959 – 968.
Haman F, Peronnet F, Kenny GP, Massicotte D, Lavoie C, Scott C, Weber JM. (2002). Effect of
cold exposure on fuel utilization in humans: plasma glucose, muscle glycogen and lipids. Journal of
Applied Physiology. 93: 77 – 84.
155
Haman F, Legault SR, Rakobowchuk M, Ducharme MB, Weber JM. (2004a). Effects of
carbohydrate availability on sustained shivering II. Relating muscle recruitment to fuel selection.
Journal of Applied Physiology. 96: 41 – 49.
Haman F, Legault SR, Weber JM. (2004). Fuel selection during intense shivering in humans: EMG
pattern reflects carbohydrate oxidation. Journal of Physiology. 556: 305 – 313.
Haman F, Peronnet F, Kenny GP, Massicotte D, Lavoie C, Scott C, Weber JM. (2005). Partitioning
oxidative fuels during cold exposure in humans: muscle glycogen becomes dominant as shivering
intensifies. Journal of Physiology. 566: 247 – 256.
Haman F. (2006). Shivering in the cold: from mechanisms of fuel selection to survival. Journal of
Applied Physiology. 100: 1702 – 1708.
Haman F, Scott CG, Kenny GP. (2007). Fuelling shivering thermogenesis during passive
hypothermic recovery. Journal of Applied Physiology. 103: 1346 – 1351.
Hamilton RS, Paton BC. (1996). The diagnosis and treatment of hypothermia by mountain resuce
teams: a survey. Wilderness and Environmental Medicine. 1: 28 – 37.
Hanson LA, Bjorkander J, Qxelius VA. (1983). Selective IgA deficiency. In: R. K. Chandra (Ed.).
Primary and secondary immunodeficiency disorders. Edinburgh: Churchill Livingstone. 62 – 64.
Harnett RM, O’Brien EM, Sias FR, Pruitt JR. (1980). Initial treatment of profound accidental
hypothermia. Aviation, Space and Environmental Medicine. 51: 680 – 7.
Harirchi I, Arvin A, Vash JH, Zafarmand V. (2005). Frostbite: incidence and predisposing factors in
mountaineers. British Journal of Sports Medicine. 39: 898 – 901.
156
Hashmi MA, Bokhari SAH, Rashid M, Hussain T, Haleem A. (1998). Frostbite: epidemiology at
high altitude in the Karakoram mountains. Annals of Research in the College of Surgery in
England. 80: 91 – 95.
Hayward JS, Steinman AM. (1975). Accidental hypothermia: an experimental study of inhalation
rewarming. Aviation, Space and Environmental Medicine. 46: 1236 – 1240.
Hayward JS, Eckerson JD, Kemna D. (1983). Thermal and cardiovascular changes during three
methods of resuscitation from mild hypothermia. Resuscitation. 113: 1 – 13.
Hayward JS, Eckerson JD, Kemna D. (1984). Thermal and cardiovascular changes during three
methods of resuscitation from mild hypothermia. Resuscitation. 11: 21 – 33.
Hearns S. (2003). The Scottish mountain rescue casualty study. Emergency Medicine. 20: 281 –
284.
Heggie TW, Amundson ME. (2009). Dead Men Walking: Search and Rescue in US National Parks.
Wilderness and Environmental Medicine. 20: 244 – 249.
Henningsen GM, Hurrell JJ, Baker F. (1992). Measurement of salivary immunoglobulin A as an
immunologic biomarker of job stress. Scandinavian Journal of Work, Environment and Health.
18(2): 133 – 136.
Herrington TN, Morse LH. (1996). Temperature Related Disorders. Occupational Injuries:
Evaluation, Management and Prevention. Mosby, St. Louis, MO: 381 - 394.
Hervey GR. (1973). Physiological changes encountered in hypothermia. Proceedings of the Royal
Society of Medicine. 66: 1053 – 1058.
Himms-Hagen K. (1972). Lipid metabolism during cold exposure and cold acclimation. Lipids. 7:
310 – 320.
157
Himms-Hagen J. (2001). Does brown adipose tissue (BAT) have a role in the physiology or
treatment of human obesity? Reviews in Endocrine and Metabolic Disorders. 2: 395 - 401.
Hindsholm KB, Bredahl P, Hcrlevsen P, Kruhoffer PK. (1992). Reflective blankets used for
reduction of heat loss during regional anaesthesia. British Journal of Anaesthesia. 68: 531 – 533.
Hiramatsu K, Yamada T, Katakura M. (1984). Acute effects of cold on blood pressure, renin-
angiotensin-aldosterone system, catecholamines and adrenal steroids in man. Clinical and
Experimental Pharmacology and Physiology. 11: 171 – 179.
Holcomb J. (2005). The 2004 Fitts lecture: Current perspective on Combat Care. Journal of
Trauma. 59: 990 – 1002.
Hollies NRS, Goldman RF. (1977). Psychological scaling in comfort assessment. In: Hollies NRS,
Goldman RF (eds) Clothing Comfort: Interaction of Thermal, Ventilation, Construction, and
Assessment Factors. Ann Arbor Science Publishers Inc., Ann Arbor. 107 – 120.
Holmér I. (1994). Cold Stress: Part II -- The Scientific Basis (Knowledge Base) for the Guide.
International Journal of Industrial Ergonomics. 14: 151 - 159.
Holmer I, Nilsson H. (1995). Heated Manikins as a Tool for Evaluating Clothing. Annals of
occupational Hygiene. 39(6): 809 – 818.
Holmgren J, Czerkinsky C. (2005). Mucosal immunity and vaccines. Nature Medicine. 11: 45 – 53.
Horovitz BA. (1971). Brown fat thermogenesis: physiological control and metabolic basis. In
Jansky L (ed) Non-shivering thermogenesis. Academia, Prague. 221 – 240.
Horvath SM, Radcliffe CE, Hutt BK, Spurr GB. (1955). Metabolic responses of older people to a
cold environment. Journal of Applied Physiology. 8: 145 - 148.
158
Horvath SM, Spurr GB, Hutt BK, Hamilton LH. (1956). Metabolic cost of shivering. Journal of
Applied Physiology. 8: 595 – 602.
Houben H, Thien T, Wijnands G, Van’t Laar A. (1982). Effects of cold exposure on blood pressure,
heart rate and forearm blood flow in normotensives during selective and non-selective beta-
adrenoceptor blockade. British Journal of Clinical Pharmacology. 14: 867 – 870.
Housh TJ, Johnson GO, Housh DJ, Evans SL, Tharp GD. (1991). The effect of exercise at various
temperatures on salivary levels of immunoglobulin A. International Journal of Sports Medicine. 12:
498 – 500.
http://www.llanberismountainrescue.co.uk/English/Previous.php
Huber CS, Heidelbaugh ND, Rapp RM, Smith MC. (1973). Nutrition systems for pressure suits.
Aero-space Medicine. 44: 905 - 909.
Hucklebridge F, Clow A, Evans P. (1998). The relationship between salivary secretory
immunoglobulin A and cortisol: neuroendocrine response to awakening and the diurnal cycle.
International Journal of Psychophysiology. 31: 69 – 76.
Hudlicka O. (1982). Growth of capillaries in skeletal and cardiac muscle. Circulation Research. 50:
451 – 461.
Hultzer M, Xu X, Marrao M, Chochinov A, Giesbrecht GG. (1999). Efficacy of torso rewarming
using a human model for severe hypothermia. In: Procedings, World Congress on Wilderness
Medicine 1999. Whistler, Canada. Canada: Wilderness Medical Society. A80.
Iampietro PF, Vaughan JA, Goldman RF, Kreider MB, Masuccland F, Bass DE (1960). Heat
production from shivering. Journal of Applied Physiology. 15: 632 - 634.
159
Iida T. (1949). Studies concerning vascular reaction to cold (Part 1) – Physiological significance of
vascular reaction to cold (In Japanese). Journal of the Physiological Society of Japan. 11: 73 –
78.
Imms FJ, Lighten AD. (1989). The cooling effects of a cold drink. In JB Mercer (Ed). Thermal
Physiology. New York: Elsevier Science. 135 – 139.
Ingle DJ, Meeks RC, Humphrey LM. (1953). Effects of exposure to cold upon urinary nonprotein
nitrogen and electrolytes in adrenalectomised and nonadrenalectomised rats. American Journal of
Physiology. 173: 387 – 389.
ISO 9886. (2004). Ergonomics—Evaluation of Thermal Strain by Physiological Measurements.
Geneva: ISO. 1 – 21.
Issekutz B, Rodahl K, Birkhead NC. (1962). Effect of severe cold stress on the nitrogen balance of
men under different dietary condtions. Journal of Nutrition. 78: 189 – 197.
Jacobs I, Romet TT, and and Kerrigan-Brown D. (1985). Muscle glycogen depletion during
exercise at 9°C and 21°C. European Journal of Applied Physiology. 54: 35 – 39.
Jacobs I, Martineau L, Vallerand AL. (1994). Thermoregulatory thermogenesis in humans during
cold stress. In: Hollosky JO, Baltimore MD (eds) Exercise Sport Science Review. Williams and
Wilkins. 22: 221 – 250.
Janský L. (1973). Non shivering thermogenesis and its thermoregulatory significance. Biology
Review. 48: 85 – 132.
Janský L, Krámek P, Kavlíková J, Ulibný B, Janáková H, Horký K. (1996a). Changes in
sympathetic activity, cardiovascular functions and plasma hormone concentrations due to cold
water immersion in man. European Journal of Applied Physiology. 74: 148 – 152.
160
Janský L, Posposolova D, Honzova S, Ulicny B, Sramek P, Zeman V, Kaminkovfi J. (1996).
Immune system of cold-exposed and cold adapted humans. European Journal of Applied
Physiology. 72: 445 – 450.
Janský L, Vybíral S, Trubabová M, Okrouhlík J. (2008). Modulation of adrenergic receptors and
adrenergic functions in cold adapted humans. European Journal of Applied Physiology. 104: 131 –
135
Jensky-Squires NE, Dieli-Conwright CM, Rossuello A, Erceg DN, McCauley S, Schroeder ET.
(2008). Validity and reliability of body composition analysers in children and adults. British
Journal of Nutrition. 100: 859 - 65.
Johnson D, Gegel B, Burgert J, Duncklee GW, Robison RR, Lewis EJ, Crum PM, Kuhns W, Moore
D, O’Brien S, Elliot J, Washington J, Boyle J, Seigler D. (2010). Effects of the HEET garment in
the prevention of hypothermia in a porcine model. Journal of Surgical Research. 164: 126 – 130.
Johnson DG, Hayward JS, Jacobs TP, Collis ML, Eckerson JD, Williams RH. (1977). Plasma
norepinephrine responses of man in cold water. Journal of Applied Physiology. 42: 216 – 220.
Johnston CE, White MD, Wu M, Bristow GK, Giesbrecht GG. (1996). Eucapnic hypoxia lowers
human cold thermoregulatory response thresholds and accelerates core cooling. Journal of Applied
Physiology. 80(2): 422 – 429.
Jones HD, McLaren CAB. (1965). Postoperative shivering and hypoxaemia after halothane, nitrous
oxide, and oxygen anaesthesia. British Journal of Anaesthesia. 37: 35 - 41.
Jurankova E, Jezova D, Vigas M. (1995). Central stimulation of hormone release and the
proliferative response of lymphocytes in humans. Molecular and Chemical Neuropathology. 25:
213 – 223.
161
Jurkovic GJ, Greiser WB, Luterman A. Curreri PW. (1987). Hypothermia in trauma victims: an
ominous predictor of survival. Journal of Trauma. 27: 1019-1024.
Kanzenbach TL, Dexter WW. (1999). Cold injuries: protecting your patients from the dangers of
hypothermia and frostbite. Postgraduate Medicine. 105(1): 72 – 78.
Kaplan JA, Guffin AV. (1985). Shivering and changes in mixed venous oxygen saturation after
cardiac surgery. Anesthesia and Analgesia. 64: 235 - 239.
Keast D, Cameron K, Morton AR. (1988). Exercise and the immune response. Sports Medicine. 5:
248 – 267.
Klokker M, Kharazmi A, Galbo H, Bygbjerg I, Pedersen BK. (1993). Influence of in vivo hypobaric
hypoxia on function of lymphocytes, neutrocytes, natural killer cells, and cytokines. Journal of
Applied Physiology. 74: 1100 – 1106.
Klokker M, Kjaer M, Secher NH, Hanel B, Warm L, Kappel M, Pedersen BK. (1995). Naturawl
killer cell response to exercise in humans: effect of exercise and epidural anaesthesia. Journal of
Applied Physiology. 78: 709 – 716.
Kornberger E, Mair P. (1996). Symposium Article: Important aspects in the treatment of severe
accidental hypothermia: The Innsbruck Experience. Journal of Neurosurgical Anaesthesiology. 8:
83 – 87.
Kottke F J, Phalen JS, Taylor CB, Visscher MB, Evans GT. (1948). Effects of hypoxia upon
temperature regulation of mice, dogs and man. American Journal of Physiology. 153: 10 - l5.
Kurz A, Sessler DI, Annadata R, Dechert M, Christensen R, Bjorksten AR. (1995). Midazolam
minimally impairs thermoregulatory control. Anesthesia and Analgesia. 81: 939 – 398.
162
Kurz A, Sessler DI, Lenhardt R. (1996). Perioperative normothermia to reduce the incidence of
surgical wound infection and shorten hospitalisation. New England Journal of Medicine. 334: 1209
– 1215.
Lackovic V, Borecky L, Vigas M, Rovensky J. (1988). Activation of NK cells in subjects exposed
to mild hyper- or hypothermic load. Journal of Interferon Research. 8: 393 – 402.
Laing SJ, Jackson AR, Walters R, Lloyd-Jones E, Whitham M, Maassen N, Walsh NP. (2008).
Human blood neutrophil response to prolonged exercise with and without a thermal clamp. Journal
of Applied Physiology. 104: 20 – 26.
Launay JC, Besnard Y, Guinet-Lebreton A, Savourey G. (2006). Acclimation to intermittent
hypobaric hypoxia modifies responses to cold at sea level. Aviation, Space and Environmental
Medicine. 77: 1230 – 1235.
Lavoy ECP, Mcfarlin BK, Simpson RJ. (2011). Immune responses to exercise in a cold
environment. Wilderness and Environmental Medicine. 22: 343 – 351.
Lee JKW, Shirrefs SM, Maughan RJ. (2008). Cold drink ingestion improves exercise endurance
capacity in the heat. Medicine and Science in Sports and Exercise. 40(9): 1637 – 1644.
Lehrer RI, Ganz T. (2002). Cathelicidins: a family of endogenous antimicrobial peptides. Current
Opinion in Hematology. 9: 18 – 22.
Lennard TWJ, Shenton BK, Borzotta A, Donnally PK, White M, Gerriet LM, Proud G, Taylor
RMR. (1985). The influence of surgical operations on components on the human immune system.
British Journal of Surgery. 72: 771 – 776.
Lewis T. (1930). Observations upon the reactions the vessels of the human skin to cold. Heart. 15:
177 – 208.
163
Lichtenstein SV, Ashe KA, el Dalati H, Cusimano RJ, Panos A, Slutsky AS. (1991). Warm heart
surgery. The Journal of Thoracic and Cardiovascular Surgery. 101: 269 – 274.
Light IM, Dingwall RHM, Norman JN. (1980). The thermal protection offered by lightweight
survival systems. Aviation, Space and Environmental Medicine. 51(10): 1100 - 1103.
Light IM, Norman JN. (1990). The thermal properties of a survival bag incorporating metallised
plastic sheeting. Aviation, Space and Environmental Medicine. 51(4): 367 - 370.
Lim PK, Luft VC. (1960). Body temperature in hypoxia. Physiologist. 3(3): 105.
Lindahl SG. (1997). Sensing cold and producing heat. Anesthesology. 86: 758 – 759.
Lloyd EL. (1973). Accidental hypothermia treated by central rewarming through the airway. British
Journal of Anaesthesia. 45: 41 – 47.
Lloyd EL. (1994). Temperature and Performance in Cold. British Medical Journal. 309: 531 - 534.
Lopez LR, Cantella RA, Piscoya Z, Colichon AA, Delgado M, Recavarren S. (1975).
Immunological survey in high altitude: effect on antibody production and the complement system.
Ann Sclavo. 17: 769 – 785.
MacGregor AR. (1988). The nature and causes of injuries sustained in 190 Scottish mountain
accidents: summary report. Scottish Sports Council. 1: 2 – 11.
Macintyre PE, Pavlin EG, Dwersteg JF. (1987). Effect of meperidine on oxygen consumption,
carbon dioxide production, and respiratory has exchange in postanesthesia shivering. Anesthesia
and Analgesia. 66: 751 – 755.
164
Mackinnon LT, Hooper S. (1994). Mucosal (secretory) immune system responses to exercise of
varying intensity and during overtraining. International Journal of Sports Medicine. 15: 179 –
183.
MacNaughton K, Sathasivam P, Vallerand A, Graham T. (1990). Influence of caffeine on metabolic
responses of men at rest in 28 and 5°C. Journal of Applied Physiology. 68: 1889 – 1895.
Malanda UL, Reulen JPH, Saris WHM, van Marken Lichtenbelt WD. (2008). Hypoxia induces no
change in cutaneous thresholds for warmth and cold sensation. European Journal of Applied
Physiology. 104: 375 – 381.
Malhotra MS, Selvamurthy W, Purkayasha SS, Mukherjee AK, Mathew L, Dua GL. (1976).
Responses of the autonomic nervous system during acclimatization to high altitude in man. Aviation
Space and Environmental Medicine. 47: 1076 – 1079.
Malavolti M, Mussi C, Poli M, Fantuzzi AL, Salvioli G, Battistini N, Bedogni G. (2003). Cross
calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry
for the assessment of total and appendicular body composition in healthy subjects aged 21-82
years. Annals of Human Biology. 30: 380 - 91.
Mandel ID. (1989). The role of saliva in maintaining oral homeostasis. The Journal of the
American Dental Association. 119: 298 – 304.
Marcus P, Robertson D, Langford R. (1977). Metallised plastic sheeting for use in survival.
Aviation, Space and Environmental Medicine. 48(1): 50 - 52.
Marshall TJ Jr. (2005). Combat casualty care: The alpha surgical company experience during
operation Iraqi freedom. Military Medicine. 170: 469 - 472.
165
Martineau L, Jacobs I. (1988). Muscle glycogen utilization during shivering thermogenesis in
humans. Journal of Applied Physiology. 65(5): 2046 - 2050.
Martineau L, Jacobs I. (1989a). Free fatty acid availability and temperature regulation in cold water.
Journal of Applied Physiology. 67: 2466 – 2472.
Martineau L, Jacobs I. (1989b). Muscle glycogen availability and temperature regulation in humans.
Journal of Applied Physiology. 66: 72 – 78.
Martineau L, Jacobs I. (1991). Effects of muscle glycogen and plasma FFA availability on human
metabolic responses in cold water. Journal of Applied Physiology. 71: 1331 – 1339.
Masoro EJ. (1966). Effect of cold on metabolic use of lipids. Physiology Review. 46: 67 - 101.
Mathew L, Purkayastha SS, Selvamurthy W, Malhortra MS. (1977). Cold induced vasodilation and
peripheral blood flow under cold stress in man at altitude. Aviation, Space and Environmental
Medicine. 48: 497 – 500.
Mathew L, Purkayastha SS, Jayashankar A, Sharma RP. (1979). Responses of high altitude natives
to a standard cold test at sea level. Aviation, Space and Environmental Medicine. 50: 372 -
375.
Mazzeo RS, Wolfel EE, Butterfield GE, Reeves JT. (1994). Sympathetic responses during 21 days
at high altitude (4300m) as determined by urinary and arterial catecholamines. Metabolism. 43:
1226 – 1232.
Mazzeo RS, Brooks GA, Butterfield GE, Podolin DA, Wolfel EE, Reeves JT. (1995).
Acclimatization to high altitude increase muscle sympathetic activity both at rest and during
exercise. American Journal of Physiology. 269: 201 – 207.
166
Mazzeo RS, Donovan D, Fleshner M, Butterfield GE, Zamudio S, Wolfel EE, Moore LG. (2001).
Interleukin-6 response to exercise and high altitude exposure: Influence of α-adrenergic blockade.
Journal of Applied Physiology. 91: 2143 – 2149.
Mazzeo RS, Dubay A, Kirsch J, Braun B, Butterfield GE, Rock PB, Wolfel EE, Zamudio S, Moore
LG. (2003). Influence of alpha-adrenergic blockade on the catecholamine response to exercise at
4300 meters. Metabolism. 52: 1471 – 1477.
Mazzeo RS. (2005). Altitude, exercise and immune function. Exercise Immunology Review. 11: 6 –
16.
McNabb PC, Tomasi TB (1981). Host defense mechanisms at mucosal surfaces. Annual Review of
Microbiology. 35: 477 – 496.
Meehan RT. (1987). Immune suppression at high altitude. Annals of Emergency Medicine. 16: 974
– 979.
Meehan RT, Duncan U, Neale L, Taylor G, Muchmore H, Scott N, Ramsey K, Smith E, Rock P,
Goldblum R, Houston C. (1988). Operation Everest II: Alterations in the immune system at high
altitudes. Journal of Clinical Immunology. 8: 397 – 406.
Mekjavic IB, Eiken O. Inhalation rewarming from hypothermia: An evaluation in -20°C simulated
field conditions. Aviat. Space Environ. Med. 1995; 66: 424–9.
Mercer JB. (1991). The shivering response in animals and man. Archives of Medical Research. 50:
18 – 22.
Mills WJ, Hackett PH, Schoene RB, Roach R, Mills WI. (1987). Treatment of hypothermia: in the
field. In: Sutton JR, Houston CS, Coates G (eds) Hypoxia and Cold. New York. Praeger. 271 –
285.
167
Mirrakhimov MM, Kitayev MI. (1979). Problems and prospects of high altitude immunology.
Vestnik Akademii Meditsinskikh Nauk SSSR. 4: 64 – 69.
Mishra SK, Segal E, Gunter E, Kurup VP, Mishra J, Murali PS, Pierson DL, Sandoysky-Losica H,
Stevens DA. (1994). Stress, immunity and mycotic diseases. Journal of Medicine and Veterinary
Mycology. 32(1): 379 – 406.
Monto AS. (2002). Epidemiology of viral respiratory infections. American Journal of Medicine.
112: 4S – 12S.
Moran D, Heled Y, Shani Y, Epstein Y. (2003). Hypothermia and local cold injuries in combat and
non-combat situations – The Israeli experience. Aviation, Space and Environmental medicine. 74:
281 – 284.
Moritz A, Henriques F. (1947). Studies of thermal injury: II. The relative importance of time and
surface temperature in the causation of cutaneous burns. American Journal of Pathology. 23: 695 –
720.
Morse DR, Schacterle GR, Eposito JV, Chod SD, Furst ML, DiPonziano J, Zaydenberg M. (1983).
Stress, meditation and saliva: A study of separate salivary gland secretions in endodontic patients.
Journal of Oral Medicine. 38: 150 – 160.
Moss J. (1986). Accidental severe hypothermia. Surgery, Gynecology and Obstetrics. 162(5): 501 –
513.
Mourtzoukou EG, Falagas ME. 2007. Exposure to cold and respiratory tract infection. International
Journal of Tuberculosis and Lung Disease. 11: 938 – 943.
168
Muchmore HT, Parkinson AJ, Scott EN. (1981). Nasopharyngeal secretory immune and
nonimmune substances in personnel at South Pole, 1978 winter-over period. Antarctic Journal. 16:
181 – 183.
Muphy JV, Banwell PE, Roberts AH, McGrouther DA. (2000). Frostbite: pathogenesis and
treatment. The Journal of Trauma. 48: 171 – 178.
Mylona E, Fahlman MM, Morgan AL, Boardly D, Tsivitse SK. (2002). S-IgA response in females
following a single bout of moderate exercise in cold and thermo-neutral environments.
International Journal of Sports Medicine. 23: 453 – 456.
Nair CS, Malhotra MS, Tiwari OP, Gopinath RM. (1971). Effect of altitude acclimatization and
cold on cold pressor response in man. Aerospace Medicine. 42: 991 – 994.
Nayha S. (2005). Environmental temperature and mortality. International Journal of Circumpolar
Heatlh. 64: 451 – 458.
Neemisha J, Lodha R, Kabra SK. (2001). Upper respiratory tract infections. Indian Journal of
Pediatrics. 68: 1135 – 1138.
Neufer PD, Young AJ, Sawka MN, Muza SR. (1988). Influence of skeletal muscle glycogen on
passive re-warming after hypothermia. Journal of Applied Physiology. 65: 805 – 810.
Ng V, Koh D, Chan G, Ong HY, Chai SE, Ong CN. (1999). Are salivary immunoglobulin A and
lysozyme biomarkers of stress amoung nurses? Journal of Occupational and Environmental
Medicine. 41: 920 – 927.
Nieman DC, Nehlsen-Cannarella SL. (1991). The effects of acute and chronic exercise on
immunoglobulins. Sports Medicine. 11: 183 – 201.
169
Nieman DC. (2000). Is infection risk linked to exercise workload? Medicine and Science in Sports
and Exercise. 32(7): 406 – 411.
Nieman DC, Henson DA, Austin MS, Sha W. (2011). Upper respiratory tract infection is reduced in
physically fit and active adults. British Journal of Sports Medicine.45: 987 – 992.
Norderhaug IN, Johansen FE, Schjerven H, Brandtzaeg P. (1999). Regulation of the formation and
external transport of secretory immunoglobulins. Clinical Reviews in Immunology. 19: 481 – 508.
Oliver SJ, Laing SJ, Wilson S, Bilzon JL, Walters R, Walsh NP. (2007). Salivary immunoglobulin
A response at rest and after exercise following a 48 h period of fluid and/or energy restriction.
British Journal of Nutrition. 97: 1109 – 1116.
Oliver SJ, Sanders SJ, Williams CJ, Smith ZA, Lloyd-Davies E, Roberts R, Arthur C, Hardy L,
MacDonald JH. (2012). Physiological and psychological illness symptoms at high altitude and their
relationship with acute mountain sickness: A prospective cohort study. Journal of Travel Medicine.
19: 210 – 219.
Patil PG, Apfelbaum JL, Zacny JP. (1995). Effects of a cold-water stressor on psychomotor and
cognitive functioning in humans. Physiology and Behaviour. 58: 1281 – 1286.
Pedersen BK, Tvede N, Klarlund K, Christensen LD, Hansen FR, Galbo H, Kharazmi A, Halkjaer-
Kristensen J. (1990). Indomethacin in vitro and in vivo abolishes post-exercise suppression of
natural killer cell activity in peripheral blood. International Journal of Sports Medicine. 11: 127 –
131.
Pedersen BK, Kappel M, Klokker M, Nielsen HB, Secher NH. (1994). The immune system during
exposure to extreme physiological conditions. International Journal of Sports Medicine. 15: 116 –
121.
170
Pedersen BK, Hoffman-Goetz. (2000). Exercise and the immune system: regulation, integration,
and adaption. Physiological Reviews. 80: 1055 – 1081.
Pedersen BK, Steensberg A. (2002). Exercise and Hypoxia: effects on leukocytes and interleukin-6
– shared mechanisms? Medicine and Science in Sports and Exercise. 34: 2004 – 2012.
Peschel A. (2002). How do bacteria resist human antimicrobial peptides? Trends in Microbiology.
10: 179 – 186.
Pocock G, Richards CD. (2006). Human Physiology: The Basis of Medicine. 3rd
edition. Oxford
University Press.
Potkanowicz ES, Caine-Bish N, Otterstetter R, Glickman EL. (2003). Age effects on thermal,
metabolic, and perceptual responses to acute cold exposure. Aviation, Space and Environmental
Medicine.74: 1157 – 1162.
Proctor DF. (1982). The mucociliary system. In: Proctor DF, Andersen I, eds. The nose. Upper
airways physiology and the atmospheric environment. Elsevier: Amsterdam. 245 – 278.
Proctor GB, Carpenter GH. (2007). Regulation of salivary gland function by autonomic nerves.
Autonomic Neuroscience. 133: 3- 18.
Proetz AW. (1953). Essays on the applied physiology of the nose, 2nd
edition. St Louis, MO: Annals
Publishing Co. 284.
Pugh LGCE. (1964). Deaths from exposure on Four Inns Walking competition, March 14-15.
Report to Medical Commission on Accident Prevention. Lancet. 1: 1210 – 1212.
Pugh LGCE. (1966). Accidental hypothermia in walkers, climbers and campers: report to the
Medical Commissions on Accident Prevention. British Medical Journal. 1: 123 – 129.
171
Pugh LGCE. (1967). Cold stress and muscular exercise, with special reference to accidental
hypothermia. British Medical Journal. 2: 333 – 337.
Purkayastha SS, Sharma RP, Ilavazhagen G, Sridharan K, Ranganathan S, Selvamurthy W. (1999).
Effect of vitamin C and E in modulating peripheral vascular response to local cold stimulus in man
at high altitude. Japanese Journal of Physiology. 49: 159 – 167.
Pyne DV, McDonald WA, Morton DS, Swigget JP, Foster M, Sonnenfeld G, Smith JA. (2000).
Inhibition of interferon, cytokine, and lymphocyte proliferative responses in elite swimmers with
altitude exposure. Journal of Interferon and Cytokine Research. 20: 411 – 408.
Radford P, Thurlow AC. (1979). Metallised plastic sheeting in the prevention of hypothermia
during neurosurgery. British Journal of Anaesthesia. 51: 237 - 240.
Ramanathan NL. (1964). A new weighting system for mean surface temperature of the human
body. Journal of Applied Physiology. 19: 531 – 533.
Rammsayer T, Hennig J, Bahner E, von Georgi R, Opper C, Fett C, Wesemann W, Netter P. (1993).
Lowering of body core temperature by exposure to a cold environment and by a 5-HT1A agonist:
effects on physiological and psychological variables and blood serotonin levels.
Neuropsychobiology. 28: 37 – 42.
Ravussin E. Schutz T, Acheson KJ, Dusmet M, Bourquin L, Jequier E. (1985). Short-term mixed
diet overfeeding in man: no evidence for “luxusconsumption”. American Journal of Physiology –
Endocrinology and Metabolism. 249: 470 – 477.
Rennie DW, Covino BG, Howell BJ, Song SH, Kang BS, Hong SK. (1962). Physical insulation of
Korean diving women. Journal of Applied Physiology. 17: 961 – 966.
172
Rennie DW. (1988). Tissue heat transfer in water: lessons from Korean divers. Medicine and
Science in Sports and Exercise. 20: 177 – 184.
Ring C, Harrison LK, Winzer A, Carroll D, Drayson M, Kendall M. (2000). Secretory
immunoglobulin A and cardiovascular reactions to mental arithmetic, cold pressor, and exercise:
effects of alpha-adrenergic blockade. Psychophysiology. 37:634 – 643.
Robinson KA, Haymes EM. (1990). Metabolic effects of exposure to hypoxia plus cold at rest and
during exercise in humans. Journal of Applied Physiology. 68(2): 720 - 725.
Robinson WA. (1992). Competing with the cold. Part II. Hypothermia. Physics of Sport Medicine.
20: 61 – 65.
Romet TT, Hoskin RW. (1988). Temperature and metabolic responses to inhalation and bath
rewarming protocols. Aviation, Space and Environmental Medicine. 59: 630 – 634.
Romet TT. (1988). Mechanism of afterdrop after cold water immersion. Journal of Applied
Physiology. 65: 1535 – 1538.
Sabiston BH, Livingstone SD. (1973). Investigation of Health Problems Related to Canadian
Northern Military Operations. Toronto, ON: Defence and Civil Inst. Environmental Medicine.
Saito M, Okamatsu-Ogura Y, Matsushita M, Watanabe K, Yoneshiro T, Nio-Kobayashi J, Iwanaga
T, Miyagawa M, Kameya T, Nakada K, Kawai Y, Tsujisaki M. (2009). High incidence of
metabolically active brown adipose tissue in healthy adult humans. Diabetes. 58: 1526 – 1531.
Sallis R, Chassay CM. (1999). Recognising and treating common cold induced injury in outdoor
sports. Medicine and Science in Sports and Exercise. 31(10): 1367 – 1373.
173
Salo M. (1992). Effects of anaesthesia and surgery on the immune response. Acta
Anaesthesiologica Scandinavica. 36: 201 – 220.
Savard GK, Cooper KE, Veale WL, Malkinson TJ. (1985). Peripheral blood flow during rewarming
from mild hypothermia in humans. Journal of Applied Physiology. 58: 4 – 13.
Savourey G, Guinet A, Besnard Y, Garcia N, Hanniquet AM, Bittel J. (1997). General and local
cold responses after 2 weeks at high altitude. European Journal of Applied Physiology. 75: 28 – 33.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. (2007). American
College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and Science in
Sports and Exercise. 39: 377 – 390.
Scholander PF, Hammel HT, Lange Anderson K and Lyning Y. (1958). Metabolic acclimation to
cold in man. Journal of Applied Physiology. 12: l - 8.
Selsted ME, Harwig SS, Ganz T, Schilling JW, Lehrer RI. Primary structures of three human
neutrophil defensins. Journal of Clinical Investigation. 76: 1436 – 1439.
Sessler DI. (1994). Termperature monitoring. In: Millar RD, ed, Anesthesia. New York: Churchill
Livingstone. 1363 – 1382.
Sharp B. (2007). Scottish Mountaineering Incidents (1996 – 2005) Research Report no. 109 A
research study for sportscotland©, Edinburgh: 1- 41.
Sheffield CW, Sessler DI, Hunt TK. (1994). Mild hypothermia during isoflurene anesthesia
decreases resistance to E. coli dermal infection in guinea pigs. Acta Anaesthesiologica
Scandinavica. 38: 201 – 205.
174
Shephard RJ. (1997). Physical activity, training and the immune response. Carmel, IN: Cooper
Publishing Group. 8 – 9.
Shephard RJ, Castellani JW, Shek PN. (1998). Immune deficits induced by strenuous exertion
under adverse environmental conditions: manifestations and countermeasures. Critical Reviews in
Immunology. 18: 545 – 568.
Shephard RJ, Shek PN. (1998). Cold exposure and immune function. Canadian Journal of
Physiology and Pharmacology. 76: 828 – 836.
Silvers WS. (1991). The skier’s nose: a model of cold-induced rhinorrhea. Annals of Allergy,
Asthma and Immunology. 67: 32 – 36.
Singh I, Chohan IS, Lal M, Khanna PK, Srivastava MC, Nanda RB, Lamba JS, Malhotra MS.
(1977). Effects of high altitude stay on the incidence of common diseases in man. International
Journal of Cell Biometerology. 21: 93 – 122.
Smith OLK, Davison SB, Davis E. (1982). Effects of acute cold exposure on muscle amino acid and
protein in rats. Journal of Applied Physiology: Respiratory, Environmental and Exercise
Physiology. 52: 1250 – 1256.
Spencer-Smith JL. (1977). The physical basis of clothing comfort Part 2: Heat transfer through dry
clothing assemblies. Clothing Research Journal. 5: 3 - 7.
Sterba JA. (1991). Efficacy and safety of prehospital rewarming techniques to treat accidental
hypothermia. Annals of Emergency Medicine. 20: 896 – 901.
Stone AA, Neale JM, Cox DS, Napoli A, Valdimarsdottir H, Kennedy-Moore E. (1994). Daily
events are associated with a secretory immune response to an oral antigen in man. Health
Psychology. 13: 440 – 446.
175
Stone AA, Cox DS, Valdimarsdottir H, Jandorf L, Neale JM. (1987). Evidence that secretory IgA
antibody is associated with daily mood. Journal of Personal and Social Psychology. 52: 988 – 995.
Takeoka M, Yanagidaira Y, Sakai A, Asano K, Fujiwara T, Yanagisawa K, Kashumura O, Ueda G,
Wu TY, Zhang Y. (1993). Effects of high altitudes on finger cooling test in Japanese and Tibetans
at Qinghai Plateau. International Journal of Biometeorology. 37: 27 – 31.
Taylor GR, Dardano JR. (1983). Human cellular immune responsiveness following space flight.
Aviation, Space and Environmental Medicine. 12: 55 – 59.
Tengerdy RP, Kramer T. (1968). Immune response of rabbits during short term exposure to high
altitude. Nature. 217: 367 – 369.
Tenovuo J. (1998). Antimicrobial function of human saliva – how important is it for oroal health?
Acta Odontologica Scandinavica. 56: 250 – 256.
The Eurowinter Group. (1997). Cold exposure and winter mortality from ischaemic heart disease,
cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe.
Lancet. 349: 1341 – 1346.
Thompson RL, Hayward JS. (1996). Wet-cold exposure and hypothermia: thermal and metabolic
responses to prolonged exercise in rain. Journal of Applied Physiology. 81: 1128 – 1137.
Tikuisis P, Bell DG, Jacobs I. (1991). Shivering onset, metabolic response, and convective heat
transfer during cold air exposure. Journal of Applied Physiology. 70: 1996 – 2002.
Tikuisis P. (1995). Predicting survival time for cold exposure. International Journal of
Biometeorology. 39: 94 – 102.
176
Tikuisis P, Ducharme MB, Moroz D, Jacobs I. (1999). Physiological responses of exercised
fatigued individuals exposed to wet cold conditions. Journal of Applied Physiology. 86: 1319 – 28.
Tikuisis P, Jacobs I, Moroz D, Vallerand AL, Martineau L. (2000). Comparison of
thermoregulatory responses between men and women immersed in cold water. Journal of Applied
Physiology. 89: 1403 – 1411.
Tikuisis P, Eyolfson DA, Xu X, Giesbrecht GG. (2002). Shivering endurance and fatigue during
cold water immersion in humans. European Journal of Applied Physiology. 87: 50 – 58.
Tiollier E, Gomez –Merino D, Burnat P, Jouanin JC, Bourrilhon C, Filaire E, Guezennec Y,
Chennaoui M. (2005a). Intense training: mucosal immunity and incidence of respiratory infections.
European Journal of Applied Physiology. 93: 421 – 428.
Tiollier E, Schmitt L, Burnat P, Fouillot JP, Robach P, Filaire E, Guezennec CY, Richalet JP.
(2005b). Living high – training low altitude training: effects on mucosal immunity. European
Journal of Applied Physiology. 94: 298 – 304.
Tipton MJ, Franks GM, Meneilly GS, Mekjavic IB. (1997). Substrate utilisation during exercise
and shivering. European Journal of Applied Physiology. 76: 103 – 108.
Tomasi TB, Trudeau FB, Czerwinski D, Erredge S. (1982). Immune parameters in athletes bedfore
and after strenuous exercise. Journal of Clinical Immunology. 2: 173 – 178.
Toner MM, McArdle WD. (1986). Physiological adjustments to man in the cold. In: Pandolf K,
Sawka MN, Gonzalez RR, eds. Human Performance Physiology and Environmental Medicine at
Terrestrial Extremes. USA: Cooper Publishing Group. 372 – 375.
Turner TB. (1995). The epidemiology, pathogenesis, and treatment of the common cold. Seminars
in Paediatric Infectious Diseases. 6: 57 - 61.
177
Vallerand AL, Lupien J, Bukowiecki LJ. (1983). Interactions of cold exposure and starvation on
glucose tolerance and insulin response. American Journal of Physiology: Endocrinology and
Metabolism. 245(8): 575 – 581.
Vallerand AL, Perusse F, Bukowiecki LJ. (1987). Cold exposure potentiates the effect of insulin on
in vivo glucose uptake. American Journal of Physiology: Endocrinology and Metabolism. 253(16):
179 – 186.
Vallerand AL, Jacobs I. (1989). Rates of energy substrates utilization during human cold exposure.
European Journal of Applied Physiology. 58: 873 – 878.
Vallerand AL, Tikuisis P, Ducharme MB, Jacobs I. (1993). Is energy substrate mobilisation a
limiting factor for cold thermogenesis? European Journal of Applied Physiology. 67: 239 –
244.
Vallerand AL, Zamecnik J, Jacobs I. (1995). Plasma glucose turnover during cold stress in humans.
Journal of Applied Physiology. 78: 1296 – 1302.
Vallerand AL, Zamecnik J, Jones PJH, Jacobs I. (1999). Cold stress increases lipolysis, FFA Ra and
TG/FFA cycling in humans. Aviation, Space and Environmental Medicine. 70: 42 – 50.
Vanggaard L. (1975). Physiological reactions to wet-cold. Aviation, Space and Environmental
Medicine. 46: 33 – 36.
van Marken Lichtenbelt WD, Vanhommerig JW, Smulders NM, Drossaerts JMAFL, Kemerink GJ,
Bouvy ND, Schrauwen P, Jaap Teule GJ. (2009). Cold-Activated Brown Adipose Tissue in Healthy
Men. New England Journal of Medicine. 360: 1500 – 1508.
178
van Ooijen AM, van Marken Lichtenbelt WD, van Steenhoven AA, Westerterp KR. (2004).
Seasonal changes in metabolic and temperature responses to cold air in humans. Physiology and
Behaviour. 82: 545 – 553.
van Ooijen AMJ, van Marken Lichtenbelt WD, van Steenhoven AA, Westerterp KR. (2005). Cold
induced heat production preceding shivering. British Journal of Nutrition. 93: 387 – 391.
Vokac Z, Hjeltnes N. (1981). Core - peripheral heat distribution during sleep and its effect on rectal
temperature. In: Reinberg A, Vieux N, Andlauer P, eds. Night and Shift Work, Biological and
Social Aspects. Advances in Biosciences. New York, NY: Pergamon Press.
Vybiral S, Lesna I, Jansky L, Zeman V. (2000). Thermoregulation in winter swimmers and
physiological significance of human catecholamine thermogenesis. Experimental Physiology. 85:
321 – 326.
Wade CE, Dacanay S, Smith RM. (1979). Regional heat loss in resting man during immersion in
25.2°C water. Aviation, Space and Environmental Medicine. 50: 590 – 3.
Wagner JA, Robinson S, Marino RP. (1974). Age and temperature regulation of humans in neutral
and cold environments. Journal of Applied Physiology. 37(4): 562 – 565.
Wallenfels K, Foldi P, Niermann H, Bender, H., Linder, D. (1978). The enzymic synthesis, by
transglucosylation of a homologous series of glycosidically substituted malto-oligosaccharides, and
their use as amylase substrates. Carbohydrate Research. 61. 359 - 368.
Walsh NP, Blannin AK, Clark AM, Cook L, Robson PJ, Gleeson M. (1999). The effects of high-
intensity intermittent exercise on saliva IgA total protein and α-amylase. Journal of Sports Sciences.
17: 129 – 134.
179
Walsh NP, Bishop NC, Blackwell J, Wierzbicki SG, Montague JC. (2002). Salivary IgA response
to prolonged exercise in a cold environment in trained cyclists. Medicine and Science in Sports and
Exercise. 34 (10): 1632 – 1637.
Walsh NP, Whitham M. (2006). Exercising in environmental extremes: a greater threat to immune
function? Sports Medicine. 36: 941 – 976.
Wassner SJ, Orloff S, Holliday MA. (1977). Protein degradation in muscle: response to feeding and
fasting in growing rats. American Journal of Physiology. 233(2): 119 – 123.
Webb P. (1986). Afterdrop of body temperature during rewarming: an alternative explanation.
Journal of Applied Physiology. 60: 385 – 390.
Weber JM, Haman, F. (2004). Oxidative fuel selection: adjusting mix and flux to stay alive. In: S.
Morris & A. Vosloo (eds) Animals and Environments. 1275: 22 – 31. Elsevier, Amsterdam, The
Netherlands.
Weber JM, Haman F. (2005). Fuel selection in shivering humans. Acta Physiologica Scandinavica.
184: 319 – 329.
Weinberg AD. (1998). The role of inhalation rewarming in the early management of hypothermia.
Resuscitation. 36: 101 – 4.
Weller AC, Greenhaff P, MacDonald IA. (1998). Physiological responses to moderate cold stress in
man and the influence of prior prolonged exhaustive exercise. Experimental Physiology. 83: 679 –
95.
Wenisch C, Narzt E, Sessler DI, Parschalk B, Lenhardt R, Kurz A, Graninger W. (1996). Mild
intraoperative hypothermia reduces production of reactive oxygen intermediates by
polymorphonuclear leukocytes. Anesthesia & Analgesia. 82: 810 – 816.
180
West NP, Pyne DB, Renshaw G, Cripps AS. (2006). Antimicrobial peptides and proteins, exercise
and innate mucosal immunity. FEMS Immunology and Medical Microbiology. 48: 293 –a 304.
Whitten BK, Burlington RF, Posiviata MA, Sidel CM, Beecher GR. (1970). Amino acid catabolism
in environmental extremes: effect of temperature and calories. American Journal of Physiology.
219(4): 1046 – 1049.
Widmaier EP, Raff H, Strang KT. (2004). Regulation of organic metabolism and energy balance. In:
Widmaier EP, Raff H, Strang KT, (eds). Vander, Sherman and Luciano’s Human Physiology: The
mechanisms of body function. Ninth Edition. McGraw Hill, New York.
Wilber RL. (2001). Current trends in altitude training. Sports Medicine. 31: 249 – 265.
Williams AB, Salmon A, Graham P, Galler D, Payton MJ, Bradley M. (2005). Rewarming of
healthy volunteers after induced mild hypothermia: a healthy volunteer study. Emergency Medicine
Journal. 22: 182 – 184.
Wilkerson JE, Raven PB, Bolduan NW, Horvath SM. (1974). Adaptations in man’s adrenal
function in response to acute cold stress. Journal of Applied Physiology. 36: 183 – 189.
Wilmore JH, Costill DL, and Larry Kenney W. (2008). Physiology of Sport and Exercise. In:
Wilmore JH, Costill DL, and Larry Kenney W (eds). Human Kinetics. Champaign. Il.
Wilson O, Goldman RF. (1970). Role of air temperature and wind in the time necessary for a finger
to freeze. Journal of Applied Physiology. 29: 658 – 664.
Wittert GA, Or HK, Livesey JH, Richards AM, Donald RA, Espiner EA. (1992). Vasopressin,
corticotrophin-releasing factor, and pituitary adrenal responses to acute cold stress in normal
humans. Journal of Clinical Endocrinology and Metabolism. 75: 750 – 755.
181
Wolvers DA, van Herpen-Broekmans WM, Logman MH, van der Wielen RP, Albers R. (2006).
Effect of a mixture of micronutrients, but not of bovine colostrum concentrate, on immune function
parameters in healthy volunteers: a randomized placebo-controlled study. Nutrition Journal. 5: 28.
World Health Organisation (2004). Energy Requirements of Adults. Report of a joint Food and
Agriculture Organisation / World Health Organisation, United Nations University expert
consultation. World Health Organisation Food and Nutrition Technical Report Series. 1: 35 – 52.
Wright AD, Fletcher RF. (1987). Acute mountain sickness. Postgraduate Medical Journal. 63: 163 –
164.
Young AJ, Castellani JW, O’Brien C, Shippee RL, Tikuisis P, Meyer LG, Blanchard LA, Kain JE,
Cadarette BS, Sawka MN. (1998). Exertional fatigue, sleep loss, and negative energy balance
increase susceptibility to hypothermia. Journal of Applied Physiology. 85: 1210 - 1217.
Zaccaria M, Ermolao A, Bonavicini P, Travain G, Varmier M. (2004). Decreased serum leptin
levels during prolonged high altitude exposure. European Journal of Applied Physiology. 92. 249 –
253.
Zanetti M, Gennaro R, Romeo D. (1995). Cathelicidins: a novel protein family with a common
proregion and a variable C-terminal antimicrobial domain. FEBS letters. 374: 1 – 5.
182
Appendix A:
Bangor University
School of Sport, Health and Exercise Sciences
Subject Information Sheet
Project Title: An Experimental Study of Practical Field Methods for Cold Casualty Protection and
Treatment during Prolonged Cold Exposure
Research Co-ordinators: Dr Sam Oliver and Dr Neil Walsh
Tel: 01248 383965 Email:s.j.oliver@bangor.ac.uk
Additional Investigators: Dr Matt Fortes, Dr Gavin Lawrence, Jenny Brierley, Alberto Dolci, Phil
Heritage, Aaron Burdett, Robin Wilson, Beth Palmer and James Firman
Invitation to take part
You are being invited to take part in a research study. Before you decide to take part it is important
for you to understand why the research is being conducted and what will be required of you should
you agree to be involved. Please take time to read the following information carefully and discuss it
with the investigators. Ask us if there is anything that is not clear or if you would like more
information.
Do I have to take part?
This is entirely your decision. If you decide to take part you will be given this information sheet to
keep and be asked to sign a consent form. If you decide to take part you are still free to
withdraw at any time without giving a reason. If you decide not to participate or withdraw during
the study, your decision will not affect your relationship with the School of Sport, Health and
Exercise Sciences, or any of the investigators involved in the study. All information collected
during the study will be treated confidentially and if you choose to withdraw then your data will be
deleted from our records.
Background
Prolonged cold exposure and becoming mildly cold is associated with impaired health and
performance. Accidents in cold and wet environments can lead to hypothermia. This is especially
the case when casualties remain stationary or are suffering from trauma with blood loss (for
example, mountaineering or car accident). In the UK average mountain rescue times are typically at
least 2 hours. It is therefore important that easily administrable and transportable cold protection
methods are developed which can be used whilst casualties wait for emergency services rescue.
Ultimately, mortality rates will be decreased if cold protection methods can be developed and
shown to reduce or maintain a casualty’s core temperature. Current field cold protection methods
have been shown to be relatively ineffective (e.g. polythene survival bag), or their effectiveness is
presently unknown (e.g. hot drinks and Blizzard Survival bags). Therefore the present investigation
aims to determine the effectiveness of polythene survival bags with hot drinks and Blizzard survival
bags with and without heat pads.
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Visit One
Project Briefing
30 minutes
Objective
To assess which field method offers optimal protection for casualties in a cold environment.
What will be expected of you?
If you decide to take part in this study there will be a number of constraints placed upon you.
During the day prior to completing a trial you will be expected:
To avoid drinking alcohol or caffeinated drinks (i.e. coffee, tea, coke and diet coke).
To avoid participating in moderate to high intensity exercise.
Whilst completing the experimental trials in the laboratory you will be expected:
To spend one whole day in the laboratory on four separate occasions.
To eat and drink only what is prescribed to you.
Arrive to the laboratory after an overnight fast (10-12 hours)
To follow the study’s timetable.
To be weighed nude (behind screens to maintain privacy).
To have four blood samples taken during each one day trial (~65 ml) totaling 16 blood
samples during the 4 week study period (~260 ml).
To provide saliva and urine samples.
To perform four cold water immersions (~13°C for a maximum of 60 minutes).
To perform four 3 hour cold air tests in 0°C.
To complete a health log 2 weeks prior, during and 2 weeks following the last trial.
You will be excluded if you are a smoker, asthmatic, diabetic, have a pacemaker or any heart
condition or you are currently taking specific types of medication or supplements.
IN TOTAL, THE STUDY WILL REQUIRE YOU TO GIVE UP 34 HOURS OF YOUR
TIME.
Summary of visits
Visit One: Project briefing and familiarisation (1 hour)
At this meeting you will be fully briefed about the requirements of the project. You will be talked
through the subject information sheet by an investigator and given the opportunity to ask any
questions. You will then leave with the information sheet so as to allow you time to discuss your
possible involvement in the study with significant others. This will also allow you additional time to
think of questions.
Visit Two
Question &
Answer
Session
(Optional)
30 minutes
Visit Three
1st
Experimental
trial
8 h
Visit Four
2nd
Experimental
trial
8 h
Visit Five
3rd
Experimental
trial
8 h
Visit Six
4rd
Experimental
trial
8 h
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You will be asked to refrain from exercise and alcohol and caffeine consumption for 24 hours prior
to each visit. At this visit you will be familiarised with the procedures for collection of saliva and
venous blood. All blood samples will be collected by a qualified member of staff from a forearm
vein using a small needle (~16 ml of blood at each collection). A saliva sample will be obtained by
asking you to dribble into a plastic container for 5 minutes. You will also be familiarised with the
cognitive function tests and also the health log which you will be asked to complete at the end of
each day.
Visit Two: Question and answer session (optional)
Visit two is provided as an additional opportunity for you to ask questions. Once you are fully
satisfied with the information and on agreement to take part in the study you will be asked to
complete an informed consent form, a medical questionnaire and make arrangements for the
following visits.
Experimental trials:
You will be required to complete four experimental trials in a random order each separated by 7
days. Each experimental trial will consist of an 8 hour period where you will be in the laboratory
under treatment conditions (Visit three, four, five and six). Including the briefing meeting,
familiarisation visit and all four experimental trials you will be required to visit the
laboratory on seven occasions for a total of ~34 hours.
Visit Three, Four, Five and Six: (8 hours)
Prior to arriving at the laboratory
You will be instructed to consume your normal daily food intake and keep a food diary of what you
ate the day before the trial. We will also provide you with your daily water requirements
(approximately 2.5 L for a 70 kg person), which will help to ensure that you are hydrated prior to
each trial. We ask that you arrive at the physiology laboratory with the appropriate clothing (i.e.
swim shorts, a second pair of dry shorts and a towel) following an overnight fast at 07:00 hours.
Experimental procedures
On arrival to the laboratory and after completely emptying your bladder and bowels, your body composition
will be estimated by a non-invasive bio-electrical impedance analysis; which requires you to stand on a set of
weighing scales. On arrival at the laboratory you will be given a rectal probe to fit, and a universal container
with which to collect a urine sample. The rectal probe will be used to monitor core temperature. You will
also be asked to wear a chest strap so that we can monitor your heart rate. You will then sit quietly for 30
minutes in the laboratory (ambient temperature ~20°C) after which blood and saliva samples will be obtained
and you will complete the cognitive function tests. You will then enter the cold water bath (~13°C) and be
immersed up to your shoulders until your core temperature has decreased to 36°C (~40 minutes). At this
point you will be withdrawn from the water. After drying and putting on your dry shorts you will enter the
environmental chamber (0°C) with one of the four survival bags. You will then be asked to sit on a chair
whilst inside the survival bag. You will be randomly assigned at each trial to one of the four practical cold
protection methods: 1. Polythene survival bag; 2. Polythene survival bag with hot drink; 3. Blizzard Survival
bag and 4. Blizzard Survival Heat bag. After getting into the survival bag and at 1 and 2 hours you will be
provided with a flavoured drink. The quantity of this drink will depend on your body weight but will be
185
similar to a large mug of tea. On one trial (trial 2) this drink will be hot, i.e. similar to that temperature of
regular tea or coffee. You will be asked to consume these drinks within 15 min. Regular measurements of
thermoregulation will be made and core temperature will be continually monitored. Cognitive function tests
and saliva samples will be obtained at one hour intervals. The experimental trials will end and you will be
removed from the chamber at 3 hours or if core temperature decreases to 35°C. Following removal from the
environmental chamber (0°C), a blood and saliva sample will be obtained and you will be wrapped in
blankets. You may be immersed in warm water to aid rewarming. One and two hours following the cold
exposure we will obtain further blood and saliva samples during which time you will sit in a comfortable
ambient temperature ~20°C with blankets or dressed in your normal clothes. During this time, your core
temperature will be monitored and you will be supervised by experimenters. In the second hour of this
recovery you will be provided with a large meal and warm drink. Following the final blood and saliva
sample you will be allowed to eat and drink freely and you will be permitted to leave when your core
temperature returns to with 0.5°C of your initial core temperature. Transport home will be provided if
required.
Advantages of taking part
A benefit of taking part in this study is that you will receive comprehensive feedback, with full
explanations, of your body composition (e.g. body fat %) and blood measures (e.g. immune
function). This feedback should help you with planning and monitoring your athletic training
program. The feedback you will receive regarding your body composition is similar to that which
many testing facilities provide as a fee-paying service. Advantages for Undergraduates from within
SSHES are that you will gain a valuable insight into the procedures and work involved in a 3rd
year
project. Additionally participation in this project can be used for skills units of the Undergraduate
portfolio.
Disadvantages of taking part The disadvantages of taking part in this study, which you will probably be most concerned about, are: 1. cold
exposure test 2. blood samples; and 3. time commitment.
1. Cold exposure: Cold tests lasting two to three hours have been safely used to stress the body’s ability to
maintain core body temperature by our research group and many others. During these cold air tests you will
likely experience some peripheral numbness and mild discomfort in your hands and feet. To minimise this
discomfort, we will provide you with thermal gloves and socks.
A number of military studies have exposed individuals to freezing and/or wet conditions following periods of
prolonged physical exercise, inadequate nutrition and sleep loss, and no medical complications were reported
after rewarming in individuals whose core temperature decreased to 35°C). In these investigations no
voluntary ‘drop out’ or medical withdrawal of subjects was reported. Additionally, in contrast to these
previous investigations in which subjects sat uncovered, the provision of survival bags in the proposed study
will provide insulation.
186
In the current investigation you will be removed from the climate chamber if your core temperature
decreases to 35°C. It is important to note that 35°C is considered the upper limit of mild hypothermia (35-
32°C), and following the removal of cold stress your thermoregulatory mechanisms are likely to steadily
recover normal core temperature (~37°C). For example, in a study using cold water immersion to reduce
core temperature to 33°C participants left to shiver post immersion were able to recover core temperature to
36°C within 1 hour.
Following removal from the chamber you will be wrapped in blankets. In addition, if your core temperature
reduces below 35°C you will be immersed up to the axilla in a warm water bath (38-42°C). This technique
has previously been used in a number of studies to rewarm participants in experiments where core
temperature is decreased to between 33-34°C. For your safety your core temperature will be monitored by a
rectal probe every minute throughout the cold exposure protocol and during the first hour of recovery period
or until your core temperature returns to within 0.5°C of their starting core temperature.
The results of this study will ensure people can be better informed as to the most effective method of cold
protection in extreme environmental conditions.
2. Blood samples: The blood samples will be taken using a smaller needle than is typically used by doctors
in your local surgery or hospital. Therefore you will likely experience only very mild discomfort i.e. like a
scratch. The quantity of blood we are taking in each visit is small (i.e. approximately one tenth of that which
would be obtained when you give blood). Additionally, qualified phlebotomists experienced at performing
this procedure will collect blood samples. To ensure you are completely happy with giving blood samples,
we will familiarise you with the blood sampling procedure on your first visit to the laboratory.
3. Time commitment: To complete all aspects of the study we will require you to visit the
laboratory on six occasions for a total of approximately 33 hours. Thus, participation in this project
satisfies the requirement in hours for the Undergraduate portfolio skills unit.
At all times you will be closely supervised by an experimenter trained in First-Aid.
Any further questions will be happily answered by Dr Sam Oliver or any of the additional investigators.
187
Appendix B:
INFORMED CONSENT TO PARTICIPATE
IN A RESEARCH PROJECT OR EXPERIMENT
Title of Research Project: The researcher conducting this project subscribes to the ethics conduct of research and to the
protection at all times of the interests, comfort, and safety of participants. This form and the
information sheet have been given to you for your own protection and full understanding of the
procedures. Your signature on this form will signify that you have received information which
describes the procedures, possible risks, and benefits of this research project, that you have received
an adequate opportunity to consider the information, and that you voluntarily agree to participate in
the project.
Having been asked by Jenny Brierley of the School of Sport, Health and Exercise Sciences at
Bangor University, to participate in a research project titled:
Effect of hypoxia on the thermoregulatory responses to cold
I have received information regarding the procedures of the experiment.
I understand the procedures to be used in this experiment and any possible personal risks to me in
taking part.
I understand that I may withdraw my participation in this experiment at any time.
I also understand that I may register any complaint I might have about this experiment to Professor
Mike Khan, Head of the School of Sport Health and Exercise Sciences, and that I will be offered the
opportunity of providing feedback on the experiment using standard report forms.
I may obtain copies of the results of this study, upon its completion, by contacting:
Jenny Brierley (Tel: 07825841523 or Email: peu474@bangor.ac.uk)
I confirm that I have been given adequate opportunity to ask any questions and that these have been
answered to my satisfaction.
I have been informed that the research material will be held confidential by the researcher.
I agree to participate in the study
NAME (please type or print legibly): __________________ _____________________________
ADDRESS: (Optional)____________ __________________________________________ ____
___________________________________________ ____________________________ _________
PARTICIPANT’S SIGNATURE: __________________________ DATE: ___ ______
RESEARCHER’S SIGNATURE: __________________________ DATE: _ ________
188
Bangor University
SCHOOL OF SPORT, HEALTH AND EXERCISE SCIENCES
1 Title of project An Experimental Study of Practical Field Methods for Cold
Casualty Protection and Treatment during Prolonged Cold
Exposure
2 Name and e-mail
address(es) of all
researcher(s)
Sam Oliver - pes60b@bangor.ac.uk
Neil Walsh – pes804@bangor.ac.uk
Gavin Lawrence - g.p.lawrence.ac.uk
Matt Fortes – pep006@bango.ac.uk
Jenny Brierley – peu474@bangor.ac.uk
Alberto Dolci – dolcialberto@gmail.com
Phil Heritage – p.heritage@bangor.ac.uk
Bethan Palmer – peu86e@bangor.ac.uk
James Firman – peu81c@bangor.ac.uk
Robin Wilson – peu833@bangor.ac.uk
Aaron Burdett – peu632@bangor.ac.uk
Please tick boxes
1 I confirm that I have read and understand the Information Sheet dated …………………. for the above study. I have had the opportunity to consider the information, ask questions and have had these answered satisfactorily.
2 I understand that my participation is voluntary and that I am free to withdraw at any time without giving a reason, without my medical care or legal rights being affected.
3 I understand that my participation is voluntary and that I am free to withdraw at any time without giving a reason. If I do decide to withdraw I understand that it will have no influence on the marks I receive, the outcome of my period of study, or my standing with my supervisor, other staff members of with the School.
4 I understand that I may register any complaint I might have about this experiment with the Head of the School of Sport, Health and Exercise Sciences, and that I will be offered the opportunity of providing feedback on the experiment using the standard report forms.
189
5 I agree to take part in the above study.
Name of Participant ………………………………………………………………….
Signature …………………………………. Date …………………………………..
Name of Person taking consent…………………………………………………….
Signature …………………………………. Date …………………………………..
WHEN COMPLETED – ONE COPY TO PARTICIPANT, ONE COPY TO RESEARCHER FILE
190
Appendix C:
PHYSIOLOGY INFORMED CONSENT
& MEDICAL QUESTIONNAIRE
Name: …………………………….
Age:………………..
Are you in good health? Yes/No
If no, please explain:
How would you describe your present level of activity? Tick intensity level and indicate approx.
duration.
vigorous moderate low intensity
Duration (Min).
How Often: < once per month
once per month
2-3 times per week
4-5 times per week
> 5 times per week
Have you suffered from a serious illness or accident? Yes/No
If yes, please give particulars:
Do you suffer, or have you ever suffered from:
Asthma Yes No
Diabetes Yes No
Bronchitis Yes No
Epilepsy Yes No
High blood pressure Yes No
Are you currently taking medication ? Yes/No
If yes, please give particulars:
Are you currently attending your GP for any condition or have you
consulted your doctor in the last three months? Yes/No
If yes, please give particulars:
Have you, or are you presently taking part in any other laboratory
experiment? Yes/No
191
PLEASE READ THE FOLLOWING CAREFULLY
Persons will be considered unfit to do the experimental exercise task if they:
have a fever, suffer from fainting spells or dizziness;
have suspended training due to a joint or muscle injury;
have a known history of medical disorders, i.e. high blood pressure, heart or lung disease;
have had hyper/hypothermia, heat exhaustion, or any other heat or cold disorder;
have anaphylactic shock symptoms to needles, probes or other medical-type equipment.
have chronic or acute symptoms of gastrointestinal bacterial infections (e.g. Dysentery,
Salmonella)
have a history of infectious diseases (e.g. HIV, Hepatitis B); and if appropriate to the study
design, have a known history of rectal bleeding, anal fissures, hemorrhoids, or any other
condition of the rectum;
DECLARATION
I agree that I have none of the above conditions and I hereby volunteer to be a participant in
experiments/investigations during the period of …………………20___.
My replies to the above questions are correct to the best of my belief and I understand that they will
be treated with the strictest confidence. The experimenter has explained to my satisfaction the
purpose of the experiment and possible risks involved.
I understand that I may withdraw from the experiment at any time and that I am under no obligation
to give reasons for withdrawal or to attend again for experimentation.
Furthermore, if I am a student, I am aware that taking part or not taking part in this experiment, will
neither be detrimental to, or further, my position as a student.
I undertake to obey the laboratory/study regulations and the instructions of the experimenter
regarding safety, subject only to my right to withdraw declared above.
Signature of Participant:………………………………………………………………..
Date:…………………………………………..
Signature of Experimenter:…………………………………………………………
Date: ………………………………………….
192
Bangor University
SCHOOL OF SPORT, HEALTH AND EXERCISE SCIENCES
Name of Participant ……..…………………………………………………………..
Age ………………………
Are you in good health? YES NO
If no, please explain
How would you describe your present level of activity?
Tick intensity level and indicate approximate duration.
Vigorous Moderate Low intensity
Duration (minutes)…………………………………………………………………….
How often?
< once per month 4-5 times per week
once per month > 5 times per week
2-3 times per week
Have you suffered from a serious illness or accident? YES NO
If yes, please give particulars:
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Do you suffer, or have you ever suffered from:
YES NO YES NO
Asthma Epilepsy
Diabetes High blood pressure
Bronchitis
Are you currently taking medication? YES NO
If yes, please give particulars:
Are you currently attending your GP for any condition or have you consulted your doctor in the last three
months? YES NO
If yes, please give particulars:
Have you, or are you presently taking part in any other laboratory experiment?
YES NO
PLEASE READ THE FOLLOWING CAREFULLY
Persons will be considered unfit to do the experimental exercise task if they:
have a fever, cough or cold, or suffer from fainting spells or dizziness;
have suspended training due to a joint or muscle injury;
have a known history of medical disorders, i.e. high blood pressure, heart or lung disease;
have had hyper/hypothermia, heat exhaustion, or any other heat or cold disorder;
have anaphylactic shock symptoms to needles, probes or other medical-type equipment;
have chronic or acute symptoms of gastrointestinal bacterial infections (e.g. Dysentery, Salmonella);
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have a history of infectious diseases (e.g. HIV, Hepatitis B); and if appropriate to the study design, have a known history of rectal bleeding, anal fissures, haemorrhoids, or any other condition of the rectum.
DECLARATION
I agree that I have none of the above conditions and I hereby volunteer to be a participant in
experiments/investigations during the period of February – June 2011
My replies to the above questions are correct to the best of my belief and I understand that they will be
treated with the strictest confidence. The experimenter has explained to my satisfaction the purpose of
the experiment and possible risks involved.
I understand that I may withdraw from the experiment at any time and that I am under no obligation to
give reasons for withdrawal or to attend again for experimentation.
Furthermore, if I am a student, I am aware that taking part or not taking part in this experiment, will neither
be detrimental to, or further, my position as a student.
I undertake to obey the laboratory/study regulations and the instructions of the experimenter regarding
safety, subject only to my right to withdraw declared above.
Signature (participant) ……………………………..…………. Date ……………………..
Print name ……………………………………………………..
Signature (experimenter) ………………….…………………. Date ……………………..
Print name ……………………………………………………….
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Bangor University
SCHOOL OF SPORT, HEALTH AND EXERCISE SCIENCES
Name of Participant ………………………………………………………………..
Researcher ………………………………………………………………………….
Date …………………………………………………
YES NO
1 Have you had any kind of illness or infection in the last two
weeks?
2 Are you taking any form of medication?
3 Do you have any form of injury?
4 Have you eaten in the last hour?
5 Have you consumed any alcohol in the last 24 hours?
6 Have you performed exhaustive exercise in the last 48 hours?
IF THE ANSWER TO ANY OF THE ABOVE IS 'YES', THEN YOU MUST CONSULT A MEMBER OF STAFF BEFORE
UNDERGOING ANY EXERCISE TEST.
Signature (participant) …………………………………………… Date ………………….
Print name …………………………………………………………
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Appendix D:
McGinnis Thermal Comfort Scale
1.So cold I am helpless
2.Numb with cold
3.Very cold
4.Cold
5.Uncomfortably cold
6.Cool but fairly comfortable
7.Comfortable
8.Warm but fairly comfortable
9.Uncomfortably warm
10. Hot
11. Very hot
12. Almost as hot as I can stand
13. So hot I am sick and nauseated
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Appendix E:
100
90
80
70
60
50
40
30
95
85
75
65
45
55
35
25
20
10
15
5
3
7
0
21
13
120
110
• Absolute maximum
”Maximal”
Very strong
Strong Heavy
Somewhat strong
Moderate
Weak
Very weak
Extremely weak Minimal
Nothing at all
Light
Extremely strong
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Appendix F:
Shivering Intensity Scale – Observer rating scale
0 = No shivering activity
1 = Mild shivering in bursts
2 = Generalised but discontinuous
shivering
3 = Very marked and continued shivering
movements.
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Appendix G:
PAIN SENSATION SCALE
1 = BARELY COOL
2 = COOL, NO PAIN
3 = COLD, NO PAIN
4 = SLIGHT PAIN
5 = MILD PAIN
6 = MODERATE PAIN
7 = MODERATE – STRONG PAIN
8 = STRONG PAIN
9 = SEVERE PAIN
10 = UNBEARABLE PAIN
200
Appendix H:
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Appendix I:
A cross-sectional study examining human thermoregulation during survival bag treatment in
the cold
Accidental hypothermia affects approximately 10% of casualties reported in mountainous
environments and is a significant contributor to fatalities (Sallis and Chassay, 1999; Sharp, 2007).
Rescue times for casualties depend on global location and weather conditions. Yet even where
distances are relatively short between emergency services and a casualty (e.g. Scottish Highlands)
the reported times for evacuation are 2.25 hours by helicopter and approximately 3.5 hours when
individuals are evacuated by others means (e.g. on foot) (Crocket, 1995; Hindsholm et al. 1992).
Simple methods that prevent heat loss and promote re-warming which casualties or first-responders
can administer instantly whilst they wait for evacuation will likely reduce hypothermia related
fatalities. Polythene survival bags however, have been shown to confer no additional thermal
protection for a shivering individual compared to single layer MPS. However it remains unknown
whether triple layered MPS reduces heat loss in comparison to single polythene. PURPOSE: To
determine whether a multi-layered survival bag offers superior thermal protection compared to
single-layer polythene in the cold. METHOD: 18 individuals (13 m, 5 f) volunteered to participate.
Participants completed a 5 day wilderness expedition before being randomly assigned to one of two
groups. The groups were 1. Polythene Survival bag (PB) or 2. Blizzard Survival bag (BB). During
the trials participants wore shorts only (vests also for females) and completed a 2 h cold air test
(CAT, 0°C) in a seated position. Core temperature was assessed throughout. A two-way ANOVA
was performed on the core temperature data. RESULTS: Core temperature was not different
between the groups prior to cold exposure and no further differences occurred at any time point
throughout the CAT (Figure A.1). CONCLUSION: For normothermic, shivering individuals at
rest, a multi-layered MPS survival bag conferred no advantage in reducing heat loss compared with
a single-layer polythene bag during cold exposure.
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Figure A.1. The effect of a 120 minute cold air test on core temperature in two field cold protection
interventions (i.e. Polythene survival bag (PB, ∎); Blizzard Survival bag (BB, ◆) Values are Means
± SD.
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Appendix J.
The effect of chemical heat pads on skin temperature in 10°C, 20°C and 30°C
Chemical heat pads self activate upon contact with air and can continue to supply heat for up to 24
hours. Given thermal injury may occur when skin is heated to above 44°C (Moritz and Henriques,
1947) and survival devices incorporating chemical heat pads may be employed in ambient
conditions that are already warm (e.g. military trauma casualties), it is vital that such heat pads
situated inside survival bags do not supply heat great enough for this threshold to be reached.
PURPOSE: The purpose of this investigation was to examine skin temperature during the
application of chemical heat pads in an ambient temperature of 10°C, 20°C and 30°C. METHOD:
Three volunteers participated in the study (2 f, 1 m). Participants completed three experimental
trials in an environmental chamber wearing shorts and vests only. Trials were: 1. Blizzard Heat in
10°C, 2. Blizzard Heat in 20°C and 3. Blizzard Heat in 30°C. During each trial participants
remained seated inside the Blizzard Heat survival bag which incorporated four chemical heat pads.
Skin temperature was recorded throughout at four sites (calf, forearm, chest and thigh). Data are
presented as Means ± SD. RESULTS: The chemical heat pads did not evoke skin temperatures
above the threshold deemed to initiate thermal injury in any of the three ambient exposures (Figure
A.2). CONCLUSION: The chemical heat pads provided in a Blizzard Heat survival bag do not
cause skin temperature to rise above the threshold temperature considered to cause thermal injury
even in warm environments. This has significant benefit for trauma casualties who are predisposed
to hypothermia even in warm temperatures (e.g. military personnel).
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Appendix A.2. The effect of chemical heat pads in three ambient temperatures (10°C, 20°C and
30°C) upon skin temperature. Values are Means ± SD.