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Egan’s Chapter 35- Humidity and Bland Aerosol Therapy

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What is the primary role of the upper airway?
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Heat & moisture exchange (Specifically the nose)
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What is the process of humidity therapy?
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The nose heats and humidifies gas on inspiration, while cooling and reclaiming H2O from the gas that is exhaled
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What is humidity deficit?
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Normal humidity range (44 mg/H20) minus actual humidity
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What can happen if Isothermic saturation boundary shifts?
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The body’s normal heat and moisture exchange mechanisms can be compromised.
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What is relative humidity?
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The ratio between the amount of H2O in given volume of gas and the maximum amount it is capable of holding at that temperature.
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What is absolute humidity?
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The amount of H2O in a given volume of gas (measured in mg/L)
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What is body humidity?
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The relative humidity at body temperature (37 degrees Celsius) expressed as a percentage. Capacity of H2O at 37 Celsius is 44 mg of H2O
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What is the term for inspired air that is not fully saturated at body temperature?
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Humidity deficit
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What are purposes for administering humidification?
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**To administer dry medical gases at flows >4L/min **To overcome a humidity deficit created when the upper airway is bypassed (ET intubation) **To manage hypothermia **To treat cold air bronchospasm
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What is a humidifier?
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A device that adds molecular H2O to gas, occurring by evaporation of H2O from a surface.
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What is the temperature principle in regards to humidifier function?
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The higher the temperature of gas the more H2O it can hold.
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What is the Surface area principle in regards to humidifier function?
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Surface area affects the rate of evaporation
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What is the Time of Contact principle in regards to humidifier function?
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Evaporation increases as the contact time increases
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What is the Thermal Mass principle in regards to humidifier function?
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The greater the amount of water in the humidifier, the greater the thermal mass and capacity to hold and transfer heat to the therapeutic gas.
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What is the purpose of a BUBBLE humidifier?
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Usually used unheated with oxygen delivery systems to raise the water vapor content of gas to ambient levels by breaking underwater gas stream into small bubbles
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What is the purpose of Passover in regards to humidifiers?
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Directs gas over the water surface.
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What are two types of Passover devices?
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1. Simple reservoir type 2. Wick type: has an absorbent material that increases the surface area for dry air to interface with heated water.
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What advantages do Passover devices have over bubble humidifiers?
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**Maintains saturation at high flow rates **Adds little to no flow resistance to spontaneous breathing circuits
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What is a Heat-Moisture Exchanger (HME)?
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An often passive humidifier that is also known as an artificial nose that does not add heat or water to system. It also captures exhaled heat and moisture, which is then applied to subsequent inhalation
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What are 3 types of HMEs?
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**Simple condenser humidifier **Hygroscopic condenser humidifier **Hydrophobic condenser humidifier
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What is added by using an HME?
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30-90 mL of dead space
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What does a Humid-Heat HME do?
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Absorbs expired heat and moisture, then releases it into inspired gas.
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What does a Humid-Heat consist of mechanically?
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A supply unit with microprocessor, water pump and humidification device
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Who is a HME Booster designed for?
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Patients with minute volumes of 4-20L
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Who should NOT use a HME booster?
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pediatric and infant patients
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What does a HME booster consist of mechanically?
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A T-piece containing electrically heated element
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Which humidifier can deliver gas at 100% body humidity?
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wick humidifier
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What improves water output of bubble and Passover humidifiers?
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Heat
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Who are heating systems primarily used for?
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Patients with bypassed upper airways and those receiving mechanical ventilation
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What is a drawback of using heating systems?
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Heating inhaled gas can expose patient to a risk of airway burns.
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Hygro/Hydro prefixes both mean…
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water
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What are some types of heating elements that require energy source?
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Hot plate humidifier base, wraparound type, yolk/collar element, immersion-type heater & heated wire.
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What can you do to avoid constant refilling of humidifier reservoirs?
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Use a large water reservoir and utilize a gravity feed system.
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What are characteristics of a manual reservoir feed system?
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Simple large reservoir that is manually opened and refilled with sterile or distilled water.
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What is a drawback of manual reservoir feed systems?
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Cross contamination.
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What is a characteristic of automatic reservoir feed systems
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small inlet can be attached to a gravity-fed intravenous type bag and the tubing allows refilling without interruption. Floatation valve controls can be used to maintain humidifier reservoir fluid volume.
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What is an advantage of using automatic reservoir feed systems?
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Avoids need for constant checking and manual refilling.
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What’s wrong with that freaking compensation?
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**Poses risk to patient and caregivers **Can waste a lot of H2O **Can occlude gas flow through circuit **Can be aspirated
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How do you fix the problems due to freaking compensation?
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Can be minimized with use of water traps and heated circuits, by positioning circuits so it drains condensate away from patient, and checking humidifier and nebulizer often.
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What’s up with that cross-contamination?
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H2O in the circuit can be a source of bacterial colonization
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What can help minimize condensation to reduce the risk of colonization?
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wick or membrane type Passover humidifiers prevent formation of bacteria-carrying aerosols. No need to frequently change the circuit.
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What is bland aerosol?
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consists of liquid particles suspended in gas (O2 or air)
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What types of liquid can be used in bland aerosols?
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Sterile water & Sterile saline (hypotonic, isotonic and hypertonic)
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What is the most common device used for bland aerosol delivery?
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Large-Volume Jet Nebulizers
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How do Large-Volume Jet Nebulizers work?
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Pneumatically powered and connected directly to a flow meter and a compressed gas source. Variable air-entrainment port allows air mixing to increase flow rates and to alter the FiO2
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What is the difference between high flow and low flow oxygen devices?
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High flow devices provide 100% of the patient’s respiratory needs without inhaling uncontrolled room air. Low flow devices DON’T.
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Formula for approximation for FiO2 (low flow device)
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(4x L/m) +20
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Mechanics of Large-Volume jet nebulizer
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Liquid particles are generated by passing gas at high velocity through small et orifice. Low pressure at jet draws fluid from reservoir up siphon tube. H2O is then shattered into liquid particles. Smaller particles leave the nebulizer through the outlet port into the gas stream.
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What is an ultrasonic nebulizer?
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Electrically powered device that uses a piezoelectric crystal to generate a very fine and consistently sized aerosol.
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How does the crystal transducer in an ultrasonic nebulizer work?
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Crystal transducer converts radio waves into high-frequency mechanical vibrations that produce the aerosol. Cuplent (liquid) takes vibration energy and transmits it to what is being delivered to the patient.
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What are 5 types of airway appliances?
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**Aerosol mask **Face tent **T-tube **Tracheostomy mask
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What are all airway appliances used with and why?
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Large-bore tubing to minimize flow resistance and to prevent occlusion by the condensate.
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What are enclosures (Mist tents and hoods) used for?
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To deliver aerosol therapy to infants and children
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What are drawbacks of utilizing enclosures?
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Heat retention & CO2 build-up in tents.
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What can be done to remedy heat retention in airway enclosures?
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Handled differently by each manufacturer, Maxicool uses high fresh gas flows, others may use separate cooling devices.
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What can be done to remedy CO2 build-up in airway tents?
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High flows of fresh gas circulating continually through tent help “wash out” CO2 build up
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What are three drawbacks to bland aerosol therapy?
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1. Cross-contamination/infection 2. Environmental exposure 3. Inadequate mist production
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How do you troubleshoot bland aerosol therapy overhydration?
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careful patient selection and monitoring
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How do you troubleshoot bland aerosol therapy bronchospasm?
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Discontinue bland aerosol therapy
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How do you troubleshoot bland aerosol therapy noise?
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You don’t. These devices are noisy as hell.
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What is hypertonic NaCl solution?
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<0.9%
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What percentage is half NaCl Solution?
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0.45%
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What percentage is Isotonic (normal) NaCl solution?
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0.9%
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What is percentage Hypertonic NaCl solution?
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>0.9% (10% normally)
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What is a cost-effective, and safe method for diagnosing TB, Pneumocystis Carinii, pneumonia and lung cancer.
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Sputum induction
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What does sputum induction involve?
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short-term application of high density hypertonic saline (3%-10%) aerosols to airway.