HUMIDIFICATION DURING INVASIVE AND

NON INVASIVE MECHANICAL VENTILATION

Objectives

1. To understand humidification.2. To describe how airway heat and moisture exchange

normally occurs.3. State the effect dry gases have on the respiratory tract.4. Describe how various types of humidifiers work.5. Identify the indications, contraindications, and hazards

that pertain to humidification during mechanical ventilation

6. State how to select the appropriate therapy to condition a patient’s inspired gas.

Introduction• Humidification is a method to artificially

condition the gas used in respiration of a patient as a therapeutically modality.

• Active method is by adding heat or water or both to the device or passive which is recycling heat and humidity which is exhaled by the patient.

Indications of Humidification• Primary:• Overcoming humidity deficit created when

upper airway is bypassed• To humidify dry medical gases• Secondary:• To manage hypothermia• To treat bronchospasm caused by cold air

Clinical signs and symptoms of inadequate humidification

• Dry and non-productive cough• Atelectasis• Increased airway resistance• Increased work of breathing• Increased incidence of infection• Thick and dehydrated secretions• Complaints of substernal pain and

airway dryness

Physiology

• Heat and moisture exchange is a primary function of the upper respiratory tract, mainly the nose.

• The nasal mucosal lining is kept moist by secretions from mucous glands, goblet cells, transudation of fluid through cell walls, and condensation of exhaled humidity.

• As the inspired air enters the nose, it warms (convection) and picks up water vapor from the moist mucosal lining (evaporation), cooling the mucosal surface.

Physiology cont

• Condensation occurs on the mucosal surfaces during exhalation, and water is reabsorbed by the mucus (rehydration).

• The mouth is less effective at heat and moisture exchange than the nose because of the low ratio of gas volume to moist and warm surface area and the less vascular squamous epithelium lining the oropharynx and hypopharynx.

Principles of humidifier function

• Temperature – As the temperature of a gas increases, its ability to hold water vapour (capacity) increases and vice versa.

• Surface area – There is more opportunity for evaporation to occur with greater surface area of contact between water and gas.

• Time of contact – There is greater opportunity for evaporation to occur, the longer a gas remains in contact with water.

• Thermal mass – The higher the mass of water or core element of a humidifier, the higher its capacity to transfer or hold heat.

Method of humidification -

PASSIVE HUMIDIFIERS

Advantages of Using Passive Humidifiers DuringMechanical Ventilation

Heat and moisture exchange (HME) Known as ‘Swedish nose’ Light weight disposal device Used with mechanical ventilator or breathing

spontaneously Similar to nasopharynx It function without the additon of a water source or

electricity. It collects and conserves the patient’s expired moisture

and heat. With a filter for bacteria and viruses it become Heat and

Moisture Exchanging Filter (HMEF) Types of HMEs: simple condenser humidifiers,

hydrophobic and hygroscopic

simple condenser humidifiers high thermal conductivity -

metallic gauze, corrugated metal or parallel metal tubes

Works: breath in air cools condenser breath out the condenser will warm and humidified

Trap approximately 50% exhale moisture

Hydrophobic HMEs Hydrophobic membrane with small pores –

increased surface area Works: open pores for water mist except large

water molecule Efficient in filter bacterial and viral Expiration condenser temperature to 25˚C Inspiration condenser temperature to 10 ˚C The efficiency almost same as the

hygroscopic(70%)

Hygroscopic HMEs Material – low thermal conductivity paper, wool or even wool Paper coated with lithium chloride or calcium – to recollect the

moisture Works: exhaled: some vapor will condense and the rest will absorbed

by hygroscopic salt Inspiration: the low water pressure in the inspired air cause released

the water molecule direct from hygroscopic salt high efficiency compare to hydrophobic HMEs approximately 70% efficiency that is 40 mg/l on exhaled, 27 mg/L on

return

According to International Organization for Standardization (ISO) ideal HME should operate at 70% efficiency or better providing at least 30 mg/L water vapor.

Advantage: inexpensive easy to use Small and lightweight silent in operations do not required water, temperature monitor, alarms No burns, no danger of over hydrations and electric

shock.

Disadvantages: less effective than active humidifiers can deliver only limited humidity increased in death space (Boots et al 2006) Increased tidal volume and work of breathing Need change the HME every 24(Boots et al 1993)

or 48(Djedaini et al 1995)

Method of humidification -

ACTIVE HUMIDIFIERS

Systemic hydration

Increase the amount of fluid intake orally or intravenous

To keep our body from dehydratedTo avoid air way secretion become more

tenacious

Bubble through humidifiers (BTH) Works: inspired air – bubbled through – in cold

water that in container - gets humidified Form or mashed diffusers - produce small bubbles

- total surface area to contact with water It have pressure relived valve – open when

pressure is more than 2 psi - creates visible and audible alarm

used with facemask or canula that supplied O² Settings: gas temperature 10˚C, relative humidity

100% and absolute humidity 9.4 mg/l (St.Louis 1994, mosby)

No objective benefit(BTH + nasal canule) according to (camplebell et al 1988) but subjective report shows benefit

prevent water condense in tube that block the oxygen transfer

Bubble through humidifiers

Passover humidifiers

Works: blow gas over heated sterile water - gas absorbs the water vapour - inhaled by patient

Temperature 32˚C-36˚C, water content 33-43g/m³(Hinds & Watson)

3 type of passover humidifiers: simple reservoir type wick type membrane type

Simple reservoir Works: blows gas over the surface of the heated

water Heated water - used in the mechanical

ventilations Room temperature fluid - used in non-invasive

ventilator support Total surface of contact area between the gas and

water is very less Humidifier placed below the patient airway level

to prevent overflow of the airway by the condenser water.

Sealed the traps water to prevent contamination Used for patient with spontaneous breathing Or with ventilator circuit such - CPAP & non-

invasive ventilation

Wick humidifier have an absorbent material -

increase the total surface area of dry air to interference with heated water

wick is placed upright position in the water

Works: dry gas move in chamber - flows around the wick - absorb the heat and moisture - gas saturated with water vapour leave the chamber

No bubbling - no aerosol

Membrane type humidifiers separate the fluid from the gas

stream – use hydrophobic membrane

So only water vapour can pass through the membrane not water

No bubbling - no aerosol Advantage of Passover humidifiers

compare to bubble humidifiers it can maintain saturation at high

flows rate they add little or no resistance to

spontaneous breathing circuits minimal risk for spreading

infections.

Nebulizer Produces and disperses liquid particles in a gas stream or

aerosol mist Used - produce humidification & deliver drug Drugs such as bronchodilator, mucolytic agent and

decongestant Size of the water droplet is between 0.5 to 5µm Particles more than 5µm unable to reach the peripheral

airways Particles less 0.5µm is very light, and will come back with

expired gases without being deposited in airways 2 types of nebulizer

Large Volume Jet Nebulizers Ultrasonic nebulizers.

Large Volume Jet Nebulizers Works: by forced a jet of

high-pressure gas into a liquid - inducing shearing forces - breaking the water up into fine water particles

produces particles of size 5 to 30 µm

only 30 to 40% of particles produced are in optimal range

Most of the particles get deposited in wall of main airways

Ultrasonic nebulizer used piezoeeletric crystal - contract

and expend and produce radio wave – due to electric current.

Works: Crystal transducer converts: radio

waves into high-frequency mechanical vibrations

vibration is transmitted to the water surface

The high mechanical energy creates cavitation in the fluid

it formed a standing wave which will disperses liquid particles

When inhaled it will enter respiratory tract

Frequency of oscillation determines the size of the water particles

Aerosol size of 1 to 10 µm a 95% of particles produced are in optimal

range Particles deposited directly in airway Very effective for deliver bronchodilator Hazards from nebulizer:

cause over hydrationsHypothermiatransition of infectwheezing or bronchospasmbronchoconstriction when artificial

airway is usededema of the airway wall

Contraindications: bronchoconstriction's and history of hyperresponsiveness

Advantages and disadvantages of nebulizer

Advantages• It can carry air that fully saturated with water vapour

without heated.• We can increase the amount of the water vapour in the

inhaled air. Disadvantage• It is very expensive. • The pneumatic nebulizer needs high air flow to operate. • The ultrasonic nebulizer need electric supply to operate

thus it may cause electric shock

Indications, contraindications, complications of aerosal therapy

According to AARC clinical practice guideline, 1992Indications:• Presence of upper airway edema—cool, bland aerosol• Postoperative management of the upper airway• Need for sputum specimens or mobilization of secretionsContraindications:• Bronchoconstriction• History of airway hyperresponsivenessComplications:• Wheezing or bronchospasm• Bronchoconstriction when artificial airway is used• Infection• Overhydration• Patient discomfort

Hazards of humidification during mechanical ventilation according to AARC Clinical practice Guideline

• Hazards and complications associated with the use of heated humidifier (HH) and HME devices during mechanical ventilation include the following:

• High flow rates during disconnect may aerosolize contaminated condensate (HH)• Underhydration and mucous impaction (HME or HH)• Increased work of breathing (HME or HH)• Hypoventilation caused by increased dead space (HME)• Elevated airway pressures caused by condensation (HH)

• Ineffective low-pressure alarm during disconnection (HME)

• Patient-ventilator dyssynchrony and improper ventilator function caused by condensation in the circuit (HH)

• Hypoventilation or gas trapping caused by mucous plugging (HME or HH)

• Hypothermia (HME or HH)• Potential for burns to caregivers from hot metal

(HH)

Hazards cont

• Potential electrical shock (HH)• Airway burns or tubing meltdown if heated wire

circuits are covered or incompatible with humidifier (HH)

• Possible increased resistive work of breathing caused by mucous plugging (HME or HH)

• Inadvertent overfilling resulting in unintended tracheal lavage (HH)

• Inadvertent tracheal lavage from pooled condensate in circuit (HH)

Assessment of need

• Either an HME or an HH can be used to condition inspired gases:

• HMEs are better suited for short-term use (≤96 hours) and during transport.

• HHs should be used for patients requiring long-term mechanical ventilation (>96 hours) or for patients for whom HME use is contraindicated.

Assessment of Outcome

• Humidification is assumed to be appropriate if, on regular, careful inspection, the patient exhibits none of the listed hazards or complications.

Common problems of humidification

• Cross contamination• Condensation• Proper conditioning of inspired gas• Enviromental safety• Overhydration• Bronchospasm• Noise

Conclusion

• Humidification is a means using a device to condition the air delivered to the respiratory airways. This therapy is particularly useful for patients who are mechanically ventilated or have impaired respiratory tracts. Humidification can assist clearance of secretions when clearance mechanism is not effective or when upper airways bypassed by endotracheal tube.

• The main goal of humidification therapy is to maintain normal physiologic conditions in lower airways.

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THANK YOU BY: MELODY H. MANALO BSRT