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30 Cards in this Set
- Front
- Back
What is humidity?
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- water in a gaseous state
- water vapor - molecular water in gas |
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What is potential humidity determined by?
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- temperature & gas
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When is humidity considered saturated?
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- when the gas has reached its potential at that temperature
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What is absolute humidity?
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- amount of water weight held in the gas (mg/L)
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What is the formula for relative humidity?
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absolute humidity
___________________ x 100 potential humidity |
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How much humidity does alveolar gas hold at 37 degrees Celsius?
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- approximately 44mg/L of humidity
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What is the pressure exerted by water vapor at 37 C and 100% relative humididty (RH)?
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- 47mmHg
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What is the humidity deficit?
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- amount of humidity in alveolar gas minus the amount of humidity inspired from room air
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How is humidity normally supplied to inspired gas?
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- by nasal & oropharynx passages
- if not supplied by the nose, moisture will be taken from tracheal mucosal blanket (this will dry & thicken secretions) |
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What can inadequate humidification cause?
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- decreased ciliary activity
- decreased movement of mucus - inflammation & necrosis of pulmonary epithelium - retention of secretions - bacterial culture media - atelectasis - pneumonia |
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What are the indications for humidification?
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- to prevent dry gas from drying mucosa
- to provide near body humidity when upper airway function is impaired |
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Where does humidity retain moisture in the body?
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- in the respiratory tract
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What happens if you increase the temp. of a gas?
(examples in PowerPoint page 3) |
- you will increase the potential humidity of the gas, thus decreasing its relative humidity (& vice versa)
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If at 30 degrees Celsius, a cascade humidifier puts out 100% RH, and then the temp. is increased to 37 C, what will the resulting RH delivered to the patient be?
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- less than 100% RH
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What is aerosol?
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- water particles suspended in air
- particulate water in a gas - mist - fog |
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What is the stability of an aerosol?
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- the ability of particles to remain stable while suspended in a gas
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What are the factors affecting the stability of an aerosol?
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- concentration (# of particles; more particles bump together)
- size (large particles "rain out") - RH (low relative humidity of the gas causes particles to evaporate) |
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What is penetration (aerosol)?
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- depth of tracheobronchial tree that a particle reaches
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What is deposition (aerosol)?
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- where particles "rain out" and land at a particular area
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How does gravity influence the penetration & deposition of an aerosol?
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- the larger the particle, the more likely it is to deposit or "rain out"
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How does kinetic motion influence the deposition & penetration of an aerosol?
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- the more particles move, the more likely they are to bump together, coalesce, and rain out
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How does inertial impaction influence the penetration & deposition of aerosol?
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- when airways narrow & alter direction, particles may continue on their same path and deposit by bumping airway walls
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How does ventilatory pattern influence the penetration & deposition of aerosol?
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- alterable factor influencing deposition & retention
- IDEAL PATTERN is slow, w/ deep breaths, utilizing an inspiratory hold |
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What is clearance?
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- aerosols add liquid to the lung; the liquid must be cleared to avoid accumulation
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What are the methods of clearance?
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- mobilization of mucous blanket
- cough - lymphatic uptake - phagocytes - mechanical suctioning |
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What are the indications for aerosol?
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- to thin secretions
- improve cough - deliver medications - humidification of artificial airways |
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What are the hazards of aerosol?
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swelling of dried secretions
- causes airway obstruction - can be fatal - usually patients w/ a weak cough cause bronchospasm - reactive airways - asthma fluid overload - usually use of high output systems w/ infants - CHF |
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What are the factors influencing RH w/ equipment humidifiers?
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- TEMPERATURE!
- surface area exposure (size of the bubble) - time of contact (flow & depth of water) |
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What are the characteristics of a Passover (kosher) humidifier?
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- gas passes across the surface of water which may be heated
- cascade humidifier w/ tower removed - Wick or membrane |
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What are the characteristics of a Bubble diffuser/type humidifier?
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- gas forced through straw under water
- smaller bubble = greater RH (more surface area for gas to come into contact w/ water) - deeper water = greater RH - used w/ cannula, etc. to prevent dry gas from being delivered (most common in hospitals) - usually deliver approximately 40% RH at body temp. or less |