Thermal Agents: Cryotherapy

Basics of Heat

• Heat: a term used to describe the energy that matter can store in the form of electronic, atomic, or molecular motion.– The great the molecular motion, the greater the

heat production

Basics of Cold

• Cold: in a physical sense is a negative condition, depending on the decrease in the amount of molecular vibration that constitutes heat. The less the molecular motion, the less heat production. Thus, a sensation of cold results.

Temperature:

• Temperature is a measure of the average amount kinetic energy possessed by an individual molecule of a body (kinetic theory of heat).– Temperature is a measure of sensible heat of

cold in a body.– Temperature is expressed as Fahrenheit or

Centigrade.

Classification of temperatures: for treatment purposes, are classified as follows:

Very Cold 32 to 55 F

Cold 55 to 65 F

Cool 65 to 80 F

Neutral 80 to 92 F

Warm 92 to 98 F

Hot 98 to 104 F

Very Hot 104 Hot

Transfer of energy: heat, or the loss of hear, occurs in any of the

following ways:• Conduction: Contact

• Convection: movement

• Evaporation: through liquid-gas transfer

• Radiation: electromagnetic waves

• Conversion: transfer from one energy type to another

Factors in heat transfer Cont

• Conductivity: the power of transmitting heat, electricity or sound. A tissues conductivity is usually dependent on the water content; the higher the water content the better the conductivity – Muscle - 72-75% water and conducts well– Bone and skin are 5-16% water and poor

conductors

Factors in heat transfer Cont

• Resistance: the tissues opposition to the passage of energy– Expressed in Ohms.

• Bone and fat have high resistance

• Muscle and Skin low

Cryotherapy

• Used to describe the application of cold modalities that have a temperature range between 32° and 65° F

Cryotherapeutic Benefits

• To obtain therapeutic benefits– skin temp. must be reduced to 57 °F for optimal

decrease in local blood flow– skin temp must be reduce to 58°F for analgesia– Skin tempertaure must be reduced to 36°F to

produce intra-articular temp. changes in the knee• The temp of the skin over a joint decreased the temp in

a joint proportionally 10° F skin 6.5° F joint

– Also remember that temperature is relative!

Effects of Cold on Application Site

• Vasoconstriction

• Decreased Rate of Cell metabolism resulting in a decreased need for oxygen

• Decreased production of cellular wastes

• Reduction of inflammation

• Decreased Pain

• Decreased Muscle Spasm

Systemic Effects of Cold Exposure

• General vasoconstriction in response to cooling of the posterior hypothalamus (this happens with a .2°F of circulating blood

• Heart rate is decreased

• Respiration Decreases

• Shivering and increased muscle tone– If core temperature continues to drop this is the body’s

response to increase heat

– IN GENERSAL THIS DOES NOT OCCUR WITH ICE APPLICATION!

The Effects of Ice on Injury Response

• Indications– Acute injury or Inflam

– Acute or chronic pain

– Small 1st degree burns

– Postsurgical pain and edema

– In conjunction with rehab ex.

– Neuralgia

– Acute or chronic muscle spasm

– Spastically accompanying CNS disorders

• Contraindications– Cardiac or Resp.

involvement

– Uncovered open wounds

– Circ. Insufficiency

– Cold Allergy

– Anesthetic Skin

– Advanced Diabetes

– Raynaud’s Phenomenon

Raynaud’s Phenomenon

• A vascular reaction to cold application or stress that results in a white, red, or blue discoloration of the extremities. The fingers and toes are the first to be affected. This is a sympathetic nervous system reflex

Physiological Effects of Cold: Metabolic

– Decreased secondary cell deaths by hypoxia (swelling prevents oxygen from reaching cells). The decrease in metabolism allows them to live without as much oxygen.

– Normal body temperature is 37 ° C.– Increase above 45° C (113° F) proteins

denature

Physiological Effects of Cold: Metabolic

– Reduction of edema through decreased capillary hydrostatic pressure and decreased permeability and osmotic pressure

– Increase blood viscosity (make it thicker so it won’t flood the area as quickly)

– Decrease in chemical mediator effectiveness (they cause vasodilatation)

Physiological Effects of Cold: Metabolic

– Decreases below 15 ° C (58 Þ F) a “hunting” response (Lewis 1932) incurs

• Histamine like release yields an increase vasodilatation as a self defense response

– Arterio-venal anastomoses (artery directly to veins) allow pooling of blood in feet, hands, ears, and lips. May be place of hunting response

– Don’t go below 58 ° F and keep time shorter than 30 minutes to be on the safe side

Physiological Effects of Cold: Pain

• Local decrease in free nerve ending sensitivity

• Increases the threshold for nerve firing

• Slows synaptic activity

• Allows disruption of pain-spasm-pain cycle via analgesia

Physiological effects of cold: Hemodynamic

– Vasoconstriction from smooth muscle in arterioles

– reflex vasoconstriction from A-delta (spinal reflex to preserve body heat)

– Cold blood hits hypothalamus and may start shivering response if cold enough

– A small amount of vasoconstriction gives a 4 fold decrease in blood flow

Muscle Activity• Decreased muscle spasm by decreasing muscle

spindle activity.• Intramuscular fibers (muscle spindle) runs

parallel to fibers of the muscle. Ia and II run to dorsal horn of spinal cord and respond to stretch. As the muscle contracts the spindle contracts so it remains sensitive. Cold directly decreases the activity in the Ia and II fibers. The lower the temperature, the lower the activity.

Effects of Immediate Treatment• RICE - Rest, Ice, Compression, Elevation

– Serves to counteract the body’s initial response to injury– Rest limits scope of original injury by preventing

further trauma– Ice - function is to decrease cell’s metabolism, decrease

the need or oxygen and reduce the amount of secondary hypoxic injury by enabling tissues to live on limited oxygen and secondarily reduce pain

• Crushed ice is the ideal form of cold application during initial injury because it produces the most rapid temp. decrease.

Effects of Ice on Immediate Tx

• Compression -– decreases the pressure gradient between blood

vessels and tissue and discourages further leakage from capillaries.

– Also Encourages Lymphatic drainage– Compression Types

• Circumferential - provides even pressure• Collateral - Pressure on 2 sides (aircast)• Focal Compression - U-shaped horseshoe pads

Effects of Ice on Immediate Tx

• Elevation– Decreases the hydrostatic pressure within the

capillary beds to encourage absorption of edema by lymphatic system

– This has the greatest effect at 90° perpendicular to the ground

• at 45 ° the effect of gravity is 71% comparatively

Cryokinetics• The use of cold in conjunction with movement

– Used to decrease pain and allow for free motion through the normal ROM

– Results in more pronounced macrophage reaction, quicker hematoma resolution, increased vascular growth, faster regeneration of muscle and scar tissue

– Initiated when the underlying soft tissue and bone are intact and the pain is limiting the amount of function

Penetration depends on many factors:

• Cold has a longer wavelength than heat

• Local temperature gradient

• Treatment surface area covered

• thickness and characteristics of tissue treated (fat is an insulator, tissues with high water content have better heat transfer)

Clinical Application

• Cold Pack

• Ice Massage

• Ice Immersion

• Cryostretch

• Whirlpools

• Slides in Packet for specific review of each Clinical Application

Cold Packs

• Ice Bags,

• Reusable Cold Pack

• Instant Cold Back

• Tx time for all are 15-30 minutes– Because of lasting effects application should be no

less than 2 hours apart– For controlled Cold Therapy Units - may be applied

continuously for 24 to 48 hours post acute injury or surgery

Cold Packs• Indications

– Acute injury (may use with wet wrap)

– Acute or Chronic Pain

– Postsurgical Pain and Edema

– Shape of Body part

• Precautions– AC joint and other areas may

not be suitable for wet wrap– Tension of elastic wrap

should be enough to provide adequate compression without unwarranted pressure

– Ensure Circulation w/wrap– Frostbite - if had before

chance for reoccurrence– over large or superficial

nerves

Ice Massage

• Appropriate for delivering cold tx to small evenly shaped areas.

• Most effective for muscle spasm, contusion and other minor well-localized areas

• Duration of tx– 5-15 minutes or until

ice runs out

– if the purpose is analgesic, then stop when numb

Ice Massage• Indications

– Subacute inflam or inj– Muscle strain– Contusion– Acute or chronic pain

• Contraindications– All other ice contraind.– When pressure is not

warranted– Suspected Fx

• Precautions– Injuries where pressure

massage may be contraindicated

Ice Immersion

• Temp. 50° - 60 ° F• Time 10-20 min.• Indications

– Acute Injury or Inflam.

– Acute or Chronic Pain

– Post surgical pain

• Contraindications– Same as general

Contraindications

– Acute injury where gravity is contraindicated

Cryostretch

• “Spray and Stretch” vapocoolant

• Traditionally preformed with ethyl chloride due to its ability to quickly evaporate and cool superficial tissue

• This technique is limited to a counterirritant– simply masks the symptoms to allow for a

stretch

Cryostretch• Precautions

– Can cause frostbite – Ethyl Chloride is

extremely flammable– Ethyl Chloride is a local

anesthetic but if inhaled can become general

– It’s use is based on tradition rather than fact

• Contraindications– Allergy– Open wounds– Post/surgical– Eyes– All other cold contraind &

contraind to passive stretch

• Indications– Trigger points– Muscle spasms– Decreased ROM

Cold Whirlpools

• Duration of Tx– 15-20 minutes– Temp 50° - 60 ° F

• Indications– Decreased ROM– Cryokinetics– Subacute to chronic

inflammation– Peripheral nerve injuries

(avoid extremes)

• Contraindications– Acute conditions

where water turbulence would further irritate area

– Gravity

– Postsutural

– Skin Conditions

– All other contraindications