The simultaneous use of a heat and moisture exchanger and a heated humidifier causes critical airway occlusion in less than 24 hours.

Purpose: Heat and moisture exchangers (HMEs) and heated humidifiers (HHs) may be used together inadvertently. Such an incident occurred at our institution resulting in airway occlusion.

Material And Methods: A bench-top study was conducted to compare the incidence of airway occlusion when using (1) no airway humidification, (2) HME alone, (3) HH alone, and (4) both HME and HH in combination as part of a standard breathing circuit.