CH.39 Humidity and Bland Aerosol Therapy Flashcards
Humidity
–the interface between the atmosphere and the lungs is mediated through the fluid lining of the airway
–water in inspired gas is essential to a healthy respiratory tract
Humidity Therapy
–is the addition of water to the gas delivered to the airways
–the primary goal is to maintain normal physiologic conditions
Realtive Humidity
–ratio between amount of water in a given volume of gas and the maximum amount it is capable of holding at that temperature
–Expressed as percentage
–obtained with hygrometer
–Relative Humidity= absolute humidity * 100
Absolute Humidity
–amount of water vapor in a given volume of gas
–its measurement is expressed in mg/L
Upper airway: Nose
–humidifies gas on inspiration and cools and reclaims water from gas that is exhaled
Inhalation Via the Nose
–as the inhaled ambient air enters the nose, it warms to 28.5 C (convection)
–Picks up water vapor form the moist mucosal lining (evaporation)
–cooling the mucosal surface to 30.2 C at the end of inspiration
Exhalation Via the Nose
–the expired gas (34.1- 7C) transfers heat back to the cooler tracheal and nasal mucosa, which is 32.2 C at the end of expiration
–as the saturated gas cools, it holds less water vapor
–condensation occurs on the mucosal surface during exhalation, and water is reabsorbed by the mucus (rehydration)
–in cold environment, the formation of condensate may exceed the ability of the mucus to reabsorb water (resulting in a “runny nose”)
Mouth Inhalation
–us less effective at HME than the nose because of the low ratio of gas volume to moist and warm surface area
–when a person inhales through the mouth at normal temperature , pharyngeal temperature are approximately 3 C less than when the person breathes through the nose, with 20% less RH
Mouth Exhalation
–the RH of expired gas varies little between mouth breathing and nose breathing
