Humidification of inspired gases in the critically ill

Abstract

Humidification of inspired gases is common practice in intensive care units. We review the histological and functional effects of over and under humidification. The debate over the definition of 'ideal' humidification continues. Some authors recommend fully saturated gas at 37°C, whilst others claim that gas at 32-34°C more closely approximates normal physiology. Loss of heat through the lungs is not a significant problem for the adult patient. There is no additional benefit in using inhalational strategies to rewarm hypothermic patients. We describe the advantages and disadvantages of the devices available for humidifying inspired gases, including the relatively new active heat and moisture exchangers. Although these devices have potential advantages over hot water humidifiers in terms of cost, complexity and infection risk, clinical trials are still awaited. The choice of humidifier should be tailored to the individual patient's needs. Some patients require a greater degree of humidification than can be...