Humidification in intensive care.

The normal physiological function of the upper respiratory tract is to filter and humidify inspired air. In intensive care units the upper respiratory tract is frequently bypassed. The importance of humidifying and warming the dry, cold, piped gas is well documented. The results of lack of adequate humidification include endotracheal tube obstruction, impairment of the mucociliary elevator and altered pulmonary function. Optimal levels of humidification are as yet undefined and useful clinical markers of adequate humidification are not available. As a result there is a bewildering array of humidification devices available at present, the most recent of which are heat and moisture exchangers with or without specific filtration properties. This article reviews available data on these humidification devices, and recommends an approach to their appropriate use, based on the probable physiological needs of individual patients.