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Isothermic saturation, where is saturation and heated?
As inspired gas moves into the lungs, it achives BTPS conditions. At this point, approximately 5cm below the carina, called the isothermic saturation boundary. Above the ISB, temp and humidity decrease during inhalation. and increase during exhalation. Below the ISB, temp and RH remain constant (BTPS).
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What dry gases will do to airway?
As airway is exposed to dry air, ciliary motility is reduced, airway becomes more irritable, mucus production increases, and pulmonary secretions become inspissated (chiekened due to dehydration.)
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Temperature
Higher the temp of gas, the more water it can hold. Has more Absolute Humidity than nonheated.
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Surface area
Affects the rate of evaportation. The greater the area of contact between water and gas, more opportunity of evaportation to occur. Efficent ways to increase water/gas surface area ratio include bubble diffusion, aerosol, and "wick technologies"
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contact time
when evaportation increases, so will contact time. the longer a gas remains in contact w/ water, greater the opportunity for evaporation to occur.
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How much water is in our BTPS condition gas hold?
43.8
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Actual humidifiers we use in the hospital
- 1. Bubble humidifier
- 2. Passover humidifier
- 3. Heat and moisture exchange (HME)
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Types of passovers
- 1. Simple reservoir type
- 2. Wick type
- 3. Membrane type
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Three types of HME's
- 1. Simple condensor
- 2. Hydroscopic condensor
- 3. Hydrophobic condensor.
How they work: Most often described as "artifical nose." A typical HME is a passive humidifier, captures both heat and moisture from expired gas and returns 70% both to patient @ the next inhalation. Does not add water or heat to system.
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Condensation
Poses risk to patient and caregiver. Can waste a lot of water. It can work its way and be aspirated by patient. Condenstation can be colonized, with bacteria thus it can be infectious. All healthcare providers, should reat condensate as infectious waste. Condensate can occulde (shut) flow through circuit. It can be minimized by using water traps and heated circuits.
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Large volume jet nebs. WHat it commonly do? What's it used to generate?
Most commonly used for Bland Aerosol therapy. Liquid particles are generated by passing gas at a high velocity through small jet orfice.
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Range of output of neb. Heated vs Non Heated.
- Nonheated - Can produce 26-35 mg h20/L
- Heated - Can produce 35-55 mg h20/L
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Ultrasonic
An electrically powered device that use an preoelectric crystal to generate aerosol. Converts radio waves into high frequency mechanical vibrations that produce the aerosol. Particle size is inversley proportional to signal frequency.
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