Comparative evaluation of three heat and moisture exchangers during short-term postoperative mechanical ventilation

This study compared performance of three heat and moisture exchangers (HME) during short-term postoperative mechanical ventilation. Temperature and absolute humidity (AH) were measured at various points of the ventilatory circuit. There was no statistical difference between the groups, regarding ambient and body To, body weight, fraction of inspired oxygen, tidal volume, and respiratory rate. Only the hygroscopic HME (groups 2 and 3) provide adequate conditioning with regard to AH and To of the inspiratory gases. The performance of hydrophobic HME (group 1) was inferior and appears to be unsatisfactory. Indirect evaluation (variations of inspiratory gases and tracheal temperatures, AH of the expired gases) confirmed the superiority of the hygroscopic HME. These data suggest that humidification of inspiratory gases with a hygroscopic HME is a defensible practice during short-term postoperative mechanical ventilation. Performance of hydrophobic HME may be weak and can expose the patient to an unacceptable risk of endotracheal tube occlusion.