Conditioning inspired gases:the search for relevant physiologic end points.

Conditioning inspired gases during mechanical ventilation by adding heat and humidity is a well accepted standard of care.1 Failure to heat and humidify inspired gas in an intubated patient results in well described complications, including inspissation of secretions, deciliation, bronchospasm, airway obstruction, atelectasis, and endotracheal tube (ETT) occlusion.2 Though these issues are uniformly accepted, there remain at least 2 important unanswered questions concerning humidification: