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