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What is the importance of patient airway humidification? 

The upper respiratory tract of a person during normal breathing warms, humidifies and filters inspired air from the nose and mouth. The upper respiratory tract is lined by a warm, viscous mucous membrane and as air passes over the membrane, heat and humidity is added to the inspired air before it reaches the lower airways and lungs. This membrane is also lined with very small microscopic cilia which act as an airway protection mechanism because the cillias constant movement is designed to expel any inhaled contaminants lodged in the airway. When a person exhales, the upper airway also traps most of the heat and moisture in the exhaled breath so that it can be reused during the next inhaled breath. When a person is orally or nasally intubated, the artificial airway bypasses these important mechanisms of heat and moisture exchange that are normally performed by the upper respiratory tract. The loss of this functionality increases the risk of patient hypothermia, thickening of airway secretions and possible destruction of the airway surface. Medical gases are also delivered dry and cold which can further exacerbate this clinical condition. To help prevent this condition from happening Impact recommends that clinicians place an artificial heat and moisture exchanger or HME inline in the patients breathing circuit on all intubated patients. The HME functions as an artificial airway because it traps and re-uses the patient’s heat and moisture just like the upper respiratory tract.

Clinicians should be aware that HME’s add to the amount of a patients dead space ventilation so care should be taken that an HME is selected which has as small amount of advertised dead space as possible. The ability to humidify also differs between HME brands so it is recommended that the performance capabilities of an HME be determined before purchase. The American Association of Respiratory Care (AARC) recommends that an HME should provide a minimum of 30mg H2O/L of delivered gas at 30 C.