Humidity and aerosol therapy Flashcards
What is humidification?
The act of adding water vapor to a dry gas
T/F: water vapor cannot be seen
True
Why is humidification important?
Because we are frequently bypassing the bodies natural humidification processes
Dry air can cause irritation to lungs and respiratory tract
What is relative humidity?
How much water vapor is in the air compared to how much it could hold at that temperature
What is absolute humidity?
A measure of the actual amount of water vapor in the air regardless of the airs temperature
What is the isothermic saturation boundary?
The point at which inspired gas reaches body temp and 100% relative humidity
At what temperature does thermal injury to the airway occur?
Greater than 45 degrees celsius
What does breathing dry gas do to the ISB?
Drives it deeper into the respiratory tract
What is the goal of humidity therapy?
To provide adequate heat and humidity
To treat hypothermia
To prevent airway response to cold air
To aid in removal of thick secretions
What are the effects of inadequate humidification?
Epithelial integrity decreases
Infection
Inflammation
Disruption of mucociliary transport
Increase in mucous production
Thick secretions
Increase airway irritability
Structural damage to lung
What is an active humidifier?
Adds water, heat or both to the inspired gases
What is a passive humidifier?
A passive humidifier used exhaled heat and moisture to humidify inspired gas
Describe how a bubble humidifier works
In a bubble humidifier dry gas is directed into a water filled reservoir where the stream of gas is broken into bubbles
How does surface area affect humidity
Increasing the surface area for the gas water interface increasing the gas exposed to water
How does temperature affect humidity?
The water the gas or water is, the more water vapor it can hold
What are the 3 factors that affect the humidity output of a device?
Temperature
Surface area
Exposure time
How does exposure time affect humidity?
The time a gas is exposed to water can influence humidity
More time, more evaporation
What is the primary application of bubble humidifiers?
Humidification of oxygen delivered by a low flow nasal cannula
Describe the efficiency of a bubble bottle
Not very efficient
What are the hazards associated with bubble bottle humidifiers?
Prolonged use can result in pressure relief valve becoming dysfunctional resulting in pressure build up and bottles bursting
Flow rates greater than 10 L/min can produce aerosols which can transmit bacteria
What oxygen delivery devices can interface with a bubble bottle?
Nasal cannulas
Simple masks
Non rebreather masks
Partial rebreather masks
What are the types of passover humidifiers?
Simple passover
Membrane
Wick
What is the principle of operation of simple pass over humidifiers?
Gas flows over surface, gets humidified, then flows to patient
Low efficiency due to short contact time between gas and water
Describe membrane passover humidifiers
Consists of a jar that can be filled with water but with no conduction system for the inspired gas inside the jar
Inspired gas flows into 1 side, passover over the water surface and hydrophobic membrane on the other side and exits to the other side
What temperature range are heated humidifiers capable of delivering?
30-39 degrees celsius
How efficient are heated humidifiers?
Very
Can deliver 100% relative humidity
Describe the efficiency of membrane pass over humidifiers
Low
Exposure time and surface area are limited
Describe wick pass over humidifiers
Reservoir of water and porous material that absorbs water and provides a larger area for water and air to mix which allows for better evaporation
How are water levels maintained in a heated humidifier?
Float system and disposable containers holding sterile water
What are the suggested settings for active humidification on an invasively ventilated patient?
Humidity levels between 33 mg H2O/liter and 44 mg H2O/liter
34 - 41 degrees celsius
What device helps reduce condensation in ventilator tubing connected to a heated humidifier?
Heated wire tubing
T/F: not every patient on invasive ventilation needs humidification
False
What level of humidity should a passive humidifier be able to deliver to a invasively ventilated patient?
A minimum of 30 mg H2O/Liter
Why is active humidification suggested for NIV?
May improve adherence and comfort
When are HMEs not recommended?
Patients with low tidal volumes because they contribute additional dead space which can increase the ventilation requirement and PaCO2
What are the hazards associated with heated humidity?
Electrical shock
hypo/hyperthermia
Burns
Tubing meltdown
Pooled contaminated condensate
T/F: HMEs are recommended as a prevention strategy for VAP
False
What can pooled contaminated condensate in circuit tubing result in?
Patient ventilator asynchrony
Tracheal lavage
Nosocomial infections
When using an incubator, where should the temperature probe be placed and why
Outside of the incubator
The surrounding air temperature affects humidifier function
What kind of humidifier is a HME?
A passive humidifier
What are the downsides of HMEs?
Increase dead space
Increase work of breathing
What causes the efficiency of HMEs to decline?
Increases in tidal volume, inspiratory flow, and increased FiO2
How often to HMEs need to be changed?
Every 48 hours
When are HMEs contraindicated?
When patient has thick copious secretions
When patient circuit or patient system has leaks
Patient is hyperthermic
Patient minute volume is > 10 l/m
When is the use of HMEs most appropriate?
Short term vent patients with no special humidity needs
Post op patients who will soon be extubated
PACU patients (post anethesia care unit)
ER patients
Transport patients
Some patients on home ventilators
Some pediatric patients with trach tubes
What is the definition of an aerosol?
Suspension of solid or liquid particles in gas
Visible
What are the clinical signs and symptoms of inadequate airway humidification?
Atelectasis
Dry non productive cough
increased airway resistance
Increased work of breathing
Patient complains of substernal pain and airway dryness
Thick dehydrated secretions
What are clinical uses for aerosols?
Supplemental oxygen
Inflamed airways
Hyperthermia
Minimize bleeding following a trach
Edema
Sputum induction
Post extubation edema
How do you determine whether or not an aerosol delivery device is providing adequate humidity?
The delivered relative humidity is 100% if condensate is seen in the delivery tubing near the patients airway
What are the types of bland aerosol delivery devices?
Cool
Heated
Ultrasonic nebulizers
How are large volume jet nebulizers powered?
Pneumatically
What can nebulizer therapy be used for?
Cooling
Heating
Sputum induction
Medication
T/F: large volume jet nebs cannot deliver precise FiO2 concentrations
False
What are the patient interface options for aerosols?
Aerosol mask
Face tent
Trach collar
T-tube
What are cool bland aerosols used to treat?
Upper airway edema
Laryngotracheobronchitis
Subglottic edema
Post op management of airway
Presence of a bypassed airway
Need for sputum specimens or mobilization of secretions
What are the clinical uses for heated nebulizers
Increased humidification needs
Dry gas delivery
Artificial airways
Cold reactive airways
Hypothermia
Thick secretions
Describe ultrasonic nebulizers
Works on piezoelectric principle, crystal transducer converts electrical signal into high frequency acoustic vibrations that form waves and generate a geyser of droplets that become fine aerosol particles
What are some of the risks associated with heated jet nebulizers?
May not shut down when reservoir is empty
Not sophisticated or accurately temp control
Why might you choose an ultrasonic nebulizer over a bland aerosol large volume neb?
The ultrasonic is more efficient
What can affect the particle size and aerosol density of a ultrasonic nebulizer?
Frequency of crystal vibrations
Signal amplitude
Source and flow of gas
T/F: Ultrasonic nebs are only used for bland medication therapy
False. They can be used for bland and medication therapy
Describe humidity
Water as a gas
Molecular
Invisible
What temperature and humidity should be delivered when patients are getting gasses delivered by mouth?
20-22 degrees C
50% relative humidity (36-40 mg/L)
What temperature and humidity should be delivered when patients are getting gasses delivered to trachea?
32-40 degrees C
36-40 mg/L (> 90% relative humidity)
Describe an aerosol
A suspension
Particulate
Visible
What are the primary factors affecting aerosol delivery?
Inertia
Gravity
Diffusion
T/F: warmer gases hold more water vapor
true
T/F: Aerosols are water vapor
False
When setting up a heated large volume nebulizer to place on a patient with an ETT, what interface would you pick?
T-piece
Describe humidity
Is water in a gaseous form or water vapor
Is the act of adding water vapor to an anhydrous gas
Cannot be seen
what can inadequate humidity cause?
A disruption of the mucociliary transport system
Decreased epithelial integrity leading to inflammation and infection
An increase in mucus production
Clinical signs of inadequate humidity can include
Atelectasis
A non productive cough
Increased airway resistance
Increased WOB
Substernal pain
Thick dehydrated secretions
What devices can use heated humidifiers?
ventilators
HHFNC
CPAP machines
Why is the wick humidifier extra efficient?
has increased surface area
A patient with an artificial airway can be placed on what humidification devices?
HME
heated passover
heated wick passover
Who are HMEs usually recommended for?
Patients who will not be on the ventilator for very long
Patients who are in the post anesthesia care unit
What are the goals of heated humidity therapy
Mobility of secretions
Providing adequate heat and humidity
Preventing airway response to cold air
Treating hypothermia
