Dry and cold anesthetic gas deteriorates patient's respiratory function and body heat balance. We examined whether a humidifier with heated wire circuit might maintain core temperature and humidity of inspired gas in patient undergoing general anesthesia.

We enrolled forty ASA physical status I, II patients under general anesthesia for this study. We allocated the patients randomly into two groups with (experimental group) or without (control group) Humitube® anesthesia circuit, which delivered heated and humidified inspired anesthetic gases. We recorded the temperatures and humidity of the inspired gases throughout the surgery.

The temperatures and relative humidity of the inspired gases in experimental group were significantly greater compared to control group (36.2 ± 0.9℃, 89.5 ± 4.8% vs. 30.4 ± 1.8℃, 37.9 ± 5.9%, P < 0.05) during anesthesia. The core temperatures in experimental group were significantly greater compared to control group (36.1 ± 0.3℃ vs. 35.7 ± 0.1℃, P < 0.05) during anesthesia.

A humidifier with heated wire system for anesthesia breathing circuit is helpful to maintain core temperature and adequate humidity.