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.

Results: The simultaneous use of a HME and a HH was associated with a reduction in tidal volume (no airway humidification, P ≤ .05; HME alone, P ≤ .01; and HH alone, P ≤ .01) and an increased incidence of airway occlusion (no airway humidification, 0/7; HME alone, 0/7; HH alone, 0/7; and HME and HH in combination, 7/7; P < .0001).

Conclusions: The use of a HME and a HH in combination is likely to result in airway occlusion. Precautions should be taken to ensure that both systems are not used together in clinical practice.