Term
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Definition
| heats and humidifies gas on inspiration and cools and reclaims water from gas that is exhaled. |
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Definition
| kept moist by secretions from mucosus glands, goblet cells, transudation of fluid through cell walls, and condensation of exhaled humidity |
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Definition
| very vascular, actively regulating temperature changes in the nose, service as an active element in promoting effective heart transfer. |
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Term
| as the inspired air enters the nose... |
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Definition
| it warms (convection) and picks up water vapor from the moist mucosal lining (evaporation), cooling the mucosal surface. |
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Term
| during exhalation, the expired gas... |
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Definition
| transferes heat back to the cooler tracheal and nasal mucosa by convection. condensation occurs on the mucosal surface, and water is reabsorbed by the mucus (rehydration). |
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Term
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Definition
| in cold environments the formation of condensate may exceed the ability of the mucus to reabsorb water. |
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Term
| when a person inhales through the mouth... |
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Definition
| pharyngeal temperatures are approximately 3 degrees C less than when he/she breathes through the nose, with 20% less relative humidity. |
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Term
| inspired gas into lungs BTPS conditions |
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Definition
body temperature, 37 degrees C barometric pressure saturated with water vapor [100% RH at 37 degrees C] this point, normally approx. 5cm below the carina, is called the isothermic saturation boundary (ISB) |
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Term
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Definition
| temperature and humidity decrease during inspiration and increase during exhalation |
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Term
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Definition
| temperature and relative himidity remain constant (BTPS) |
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Term
| primary goal of humidification |
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Definition
| to maintain normal physiological conditions in the lower airways. also used to treat abnormal conditions. |
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Term
| primary indications for humidification therapy |
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Definition
humidifying dry medical gases overcoming the humidity deficit created when the upper airway is bypassed |
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Term
| secondary indications for humidification therapy |
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Definition
managing hypothermia treating brochospasm caused by cold air |
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Term
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Definition
| to become thicker in consistency, or cause something to thicken, especially by boiling or evaporation |
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Term
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Definition
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Term
| humidity is provided to airway by |
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Definition
goblet cells sub mucosal glands transudation of fluid condensation of gas |
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Term
| warmed, humidified gases are used to... |
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Definition
| prevent or treat a variet of abnormal conditions. hypothermic patients inspired gas used to raise core temperatures back to normal. also used to prevent intraoperative hypothermia. can help alleviate bronchospasm in patients who develop airway narrowing after exercise or when they breath cold air. |
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Term
| cool humidified gas is used to treat... |
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Definition
| upper airway inflammation resulting from croup, epiglottitis, and postextubation edema. this technique used most often in conjuction with bland aerosol delivery. |
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Term
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Definition
| device that adds molecular water to gas. this occurs by evaporation from a water surface, whether the surfac of water is in a reservoir or is a sphere of water in suspension (nebulization). |
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Term
| four variables affecting quality of humidifier's performance |
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Definition
temperature surface area time of contact
enthalpy |
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Term
humidifier performance temperature |
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Definition
| the greater the temperature of a gas, the more water vapor it can hold (increased capacity). |
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Term
humidifier performance surface area |
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Definition
the greater the area of contact between water and gas, the more opportunity for evaporation to occur. passover humidifiers bubble-diffusion technique spraying water particles into gas wick technologies |
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Term
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Definition
| pass gas over a large surface area of water. |
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Term
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Definition
directs a stream of gas underwater, where it is broken up into small bubbles. as the gas bubbles rise to the surface, evaporation increases the water vapor content within the bubble. for a given gas volume, the smaller the bubbles, the greater the water/air surface-area ratio. unheated, they can provide 15-20 mg/L |
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Term
| spraying water particles into gas |
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Definition
| generating an aerosol (suspension of water droplets) in the gas stream. the higher the aerosol density (number of particles per volume of gas) the greater the gas/water surface area available for evaporation. |
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Term
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Definition
| use porous water-absorbent materials to increase surface area. a wick draws water (like a sponge) into its fine honeycombed structure by means of capillary action. the surfaces of the wick increase the area of contact between the water and gas, which aids evaporation. |
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Term
Humidifier function contact time |
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Definition
| the longer a gas remains in contact with water, the greater the opportunity for evaporation to occur. |
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Term
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Definition
| ineffective over 10 lpm - cooling and condensation issues require a pop-off if the flow is restricted - at 2 psi - visual and audible At high flow rates can produce aerosols which can carry pathogen and occlude the small bore tubing |
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Term
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Definition
bubble humidifier passover humidifiers heat and moisture exchangers (HMEs) these devices are either active, actively adding heat and/or water tot he device/ patient interface, or passive, recycling exhaled heat and humidity from the patient. |
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Term
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Definition
breaks (diffuses) an underwater gas stream into small bubbles. raises the dry medical gas to ambient humidity levels. unheated, they can provide 15-20 mg/L |
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Term
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Definition
| directes gas to pass over a water surface (two types are wick type and membrane type). can maintain saturation at high flow rates. add little or no flow resistance to spontaneous breathing circuits. do not generat any aerosols, and thus pose a minimal risk for spreading infection. |
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Term
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Definition
| designed for placement in a ventilatory circuit. a cylinder of absorbent material placed upright in a water reservoir and surrounded by a heating element. as dry gas enters the chamber it flows around the wick, quickly picking up moisture and leaving the chamber fully saturated with water vapor. |
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Term
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Definition
| seperates the water from the gas stream by means of a hydrophobic membrane. water vapor molecules can easily pass through this membrane, but liquid water cannot. no liquid water in the humidifier chamber. |
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Term
Aerosol generators
large-volume jet nebulizers |
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Definition
| the most common device used to generate bland aerosol. liquid particle aerosols are generated by passing gas at a high velocity through a small "jet" orifice. unheated output = 26-35 mg H2O/L. heated = 33-55 mg H2O/L. |
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Term
| heat and moisure exchange |
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Definition
| "artificial nose". captures exhaled heat and moisture and uses it to heat and humidify the next inspiration. do not actively add heat or water to the system. meets the short-term humidification needs of spontaneously breathing patients with tracheostomy tubes. |
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Term
| three types of HMEs (heat and moisture exchangers) |
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Definition
simple condenser humidifiers hygroscopic condenser humidifiers hydrophobic condenser humidifier eliminate the problem of breathing circut condensation, many consider these devices to be helpful in preventing nosocomial infections. |
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Term
HMEs simple consenser humidifiers |
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Definition
recaptures only 50% of a patient's exhaled moisture (50% efficiency) |
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Term
HMEs hygroscopic condenser humidifiers |
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Definition
| provide higher efficiency by using a condensing element of low thermal conductivity (paper, wool, foam) and impregnating this material with a hygroscopic salt (calcium or lithium chloride). can retain more heat than simple condenser systems. salt helps capture extra moisture from exhaled gas. heated charcol (salt) 70% efficency. |
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Term
| design and performance standars for HME's set by... |
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Definition
| International Organization for Standardization (ISO) |
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Term
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Definition
| portable battery-operated system avaialbe for < $300 and ensure proper conditioning of the inspired gas. reflects only the temperature differential between the humidifier and airway sensor. |
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Term
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Definition
| consists of liquid particles suspended in a gas. administration may be accompanied by oxyen therapy. |
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Term
| heated humidifiers used mainly for... |
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Definition
| patients with bypassed upper airways and/or for those receiving mechanical ventilatory support. |
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Term
| five types of heating elements |
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Definition
- hot plate - base of the humidifier
- wraparound - surrounds the humidifier chamber
- a ylk, or collar, leement that sits between the water reservoir and the gas outlet
- an immersion type heater, with the element actually placed in the water reservoir
- a heated wire in the inspiratory limb warming a saturated wick or hollow fiber.
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Term
| servo-controlled heating system |
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Definition
| monitors temperature at or near the patients's airway using a theristor probe. the controller then adjusts heater power to achieve the desired airway temperature. |
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Term
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Definition
lower levels of humidification short term use for bypassed airways output is reduced by higher tidal volumes and higher flow rates higher resistance to flow due to moisture higher dead space filters are unnecessary |
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Term
| equipment for bland aerosol therapy |
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Definition
an aerosol generator and a delivery system.
large-volume jet nebulizers
ultrasonic nebulizers (USNs)
delivery systems include a variet of direct airway appliances and enclosures (mist tents) |
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Term
| ultrasonic nebulizers (USN) |
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Definition
| electronically powered device that uses a piezoelectric crystal to generate aerosol. this crystal transducer converts radio waves into high-frequency mechanical vibrations (sound). |
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Term
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Definition
| normally preset by the manufacturer, determines aerosol particle size. particle size is inversely proportional to signal frequency. |
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Term
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Definition
| alters the transducer's vibrational energy and thus directly affects the amount of aerosol produced. can be adjusted by the clinician. |
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Term
| to produce a high-density aerosol |
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Definition
| using an ultrasonic nebulizer (useful for sputum induction), set the amplitude high and the flow rate low. |
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Term
| bland aerosol airway appliances |
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Definition
| aerosol mask, face tent, T-tube, and tracheostomy mask. in all cases, large-bore tubing is required to minimize flow resistance and prevent occlusion by condensate. |
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Term
| to maximaize aerosol delivery per minute |
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Definition
| (when trying to help mobilize secretions), set both the flow rate and the amplitude at the maximum. |
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Term
| aerosol mask and face tent |
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Definition
| used for patients withintact upper airways |
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Term
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Definition
| used for patients who are orally or nasally intubated or who have a tracheostomy |
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Term
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Definition
| used soley for patients who have a tracheostomy |
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Term
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Definition
| used for short-term therapy for patients with intact upper airways, the aerosol mask is the device of choice. |
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Term
| mist tents and aerosol hoods |
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Definition
| used to deliver bland aerosol therapy to infants and small children. the cool aerosol provided through these enclosures promotes vasoconstriction, decreases edema, and reduces airway obstruction. |
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Term
| problems with body enclosures |
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Definition
CO2 buildup - can be reduced by providing sufficiently high gas flow rates wash out CO2 while helping maintain desired O2 concentrations.
and heat retention - Maxicool, use high fresh-gas flows to prevent heat build-up. Others incorporate a seperate cooling comparetment to cool aerosol. Ohmeda Ohio Pediatric Aerosol Tent and the Mistogen CAM-2M Tent, use electronically powered refrigeration units to cool the circulating air. |
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Term
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Definition
| useful, cost-effective, safe method for diagnosing tuberculosis, Pheumocysystis carinii pheumonia, and lung cancer. |
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Term
| aputum induction involves |
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Definition
| short term application of high-density hypertonic saline (3%-10%) aerosols to the airway to assist in mobilizing pulmonary secretions for evacuation and recovery. |
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