The Effects of the Heat and Moisture Exchanger on Humidity, Airway Temperature, and Core Body Temperature

Findings from several studies have demonstrated that the use of a heat and moisture exchanger increases airway humidity, which in turn increases mean airway temperature and prevents decreases in core body temperature. Few studies however, described the effects of the HME on relative humidity, mean airway temperature and core body temperature. The purpose of this study was to describe the effects of the HME on airway humidity and temperature and core body temperature of anesthetized patients. After induction of general endotracheal anesthesia, 16 subjects received a routine general anesthetic, and were placed on a three liter per minute flow rate of N20O2 using a standard rebreathing circle system. Forced air warming blanket set at 43C was placed one each subject, and all intravenous fluids were warmed to body temperature 37C. Each subject received a Gibeck 2S Humid-Vent placed between the endotracheal tube and the Y-piece of the breathing circuit. Humidity and temperature of inspired gases along with core body temperatures were recorded at 10 minutes, and then every 30 minutes until the end of the procedure.