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30 Cards in this Set
- Front
- Back
What are the characteristics of alveolar air?
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- 100% relative humidity
- 100% body humidity - at 37 C, alveolar gas holds approx 44mg/L of humidity - at 37 C & 100% RH, the pressure exerted by water vapor is 47mmHg |
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What is the humidity deficit?
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- the amount of humidity in alveolar gas minus the amount of humidity inspired from room air
- represents the amount of water vapor the body must add to the inspired gas to achieve saturation at body temp. |
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How is humidity normally supplied to inspired gas?
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- by the nasal & oropharynx passages
- if not supplied by the nose, moisture will be taken from tracheal mucosal blanket (will dry secretions) |
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What does the artificial nose do?
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- collects & uses the patient's own heat & exhaled humidity to condition the inhalation that follows
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What are the indications for humidity?
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- to prevent dry gas from drying mucosa
- to provide near body humidity when upper airway function is impaired (overcome humidity deficit) |
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Where does humidity retain moisture?
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- in the respiratory tract
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What are the 3 factors that influence the efficiency of humidifiers?
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- temperature
- surface area exposure (size of bubble) - time of contact (flow & depth of water) |
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How does temp. influence the efficiency of a humidifier?
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- the greater the temp. of a gas, the more water vapor it can hold
- as gas expansion & evaporation cool water in unheated humidifiers to 10 C below ambient temp., the humidifiers become less efficient |
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How does surface area affect the efficiency of a humidifier?
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- the greater the area of contact between water & gas, the more opportunity there is for evaporation to occur
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How does time of contact affect the efficiency of humidifiers?
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- the longer a gas remains in contact w/ water, the greater the opportunity for evaporation to occur
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What is the formula for relative humidity?
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RH = water vapor content/potential capacity
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What are the hazards of a humidity deficit?
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- decreased cilia activity
- decreased movement of mucus - inflammation & necrosis of pulmonary epithelium - bacterial culture media - pneumonia |
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What are the hazards of humidification?
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- potential electric shock
- hypothermia/hyperthermia - thermal injury to airway - under hydration resulting in mucus plugging - increased WOB, hypoventilation, & alveolar gas trapping as a result of mucus plugging |
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What is the difference between humidity & aerosol?
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- humidity is defined as: water in a gaseous state, water vapor, & molecular water in a gas
- aerosol is defined as water particles suspended in air or particulate water in a gas (mist/fog) |
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What are the factors that influence the deposition & retention of aerosols?
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- gravity: the larger the particle, the more likely it is to deposit or "rain out"
- kinetic motion: the more particles move, the more likely they are to bump together, coalesce, & rain out - inertial impaction: when airways narrow & alter direction, particles may continue on their same path and deposit by bumping airway walls - ventilatory pattern |
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What is the best ventilator pattern for aerosol deposition in the alveoli?
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- ideal pattern is slow, w/ deep breaths, utilizing an inspiratory hold
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What are the lung clearance methods for removal of deposited aerosol?
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- mobilization of mucus blanket
- cough - lymphatic uptake - phagocytes - mechanical suctioning |
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What are the indications for aerosol therapy?
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- thin secretions
- improve cough - deliver medications - humidification of artificial airways |
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What are the hazards of aerosol therapy?
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- swelling of dried secretions (causes airway obstruction, can be fatal, patients w/ weak cough)
- can cause bronchospasm (reactive airways, asthma) - fluid overload (edema); usually through the use of high output systems w/ infants, & CHF patients |
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What is bland aerosol therapy?
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- involves the delivery of sterile water or hypotonic, isotonic, or hypertonic saline aerosols
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What are the indications for bland aerosol therapy?
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- cool mist therapy
- thin secretions - sputum sample |
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What are the characteristics of a passover 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 bubbles = greater RH (more surface area for gas to come into contact w/ water) - deeper water = greater RH - used w/ nasal cannula & other setups to prevent dry gas from being delivered (most common in hospitals) - usually delivers approximately 40% RH at body temp. or less |
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What are the characteristics of Jet humidifiers?
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- uses Bernoulli Principle to draw gas up tube
- actually produces an aerosol that is baffled out to produce humidity - not usually heated - uncommon |
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What are the characteristics of a heated cascade humidifier?
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- uses a grid network to spread a thin layer of water through which the gas passes before delivery to patient
- gas travels down a tower through a one-way valve & grid to produce a froth - small bubbles increase surface area - liquid is heated to increase potential capacity - RH equals 100% at body temp. - gas must be heated warm enough to be at body temp. when it reaches the patient |
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What is the function of the parts of the heated cascade humidifier?
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- small port at top of tower allows patient to assist a ventilation (sensing port)
- one-way valve prevents humidity from blowing back to machine |
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What are the characteristics of the Wick humidifier?
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- heater (at or near body temp.) surrounds absorbent paper which soaks up water from the bottom of humidifier
- gas passes warm wet paper and water is evaporated - water level is maintained constant by a feed apparatus - at body temp., can deliver 100% body RH |
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What are the characteristics of a Jet nebulizer?
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- uses Bernouilli Principle: decreased pressure draws water up tube
- water sprays out, baffled into uniform size particles - pneumatically powered - allows high flow system to deliver precise FIO2 - can be heated |
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What are the different types of Jet nebulizers?
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- Large reservoir: >250ml and allows long-term nebulization (50-75% RH)
- Standard (small): <20ml, used w/ IPPB, used primarily for short-term delivery of medications - Mainstream: gas flows directly through nebulizing chamber - Sidestream: aerosol is not created in main gas flow - approx. 50% of particles in 1-5 micron size |
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What are the characteristics of a Breath-actuated nebulizer (BAN)?
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- generates aerosol only during inspiration
- can increase inhaled aerosol mass 3-4x more than conventional continuous nebulization |