Temperature and metabolic responses to inhalation and bath rewarming protocols

Rewarming of mildly hypothermic subjects was compared using three different techniques that have been suggested for use in field situations. Eight subjects were cooled for up to 1 h, on four occasions, in a filled whole-body water calorimeter controlled at 22 degrees C. Following cooling, rewarming was initiated by one of four procedures: inhalation of warmed and humidified air at 40 degrees C or 45 degrees C, immersion in 40 degrees C water, or spontaneously by shivering. Deep body temperature was recorded simultaneously at three different sites: rectal, esophageal, and auditory canal. Skin temperatures were recorded from four sites: chest, forearm, thigh, and calf. Results showed that rapid external rewarming in 40 degrees C water produced the quickest rate of rewarming and smallest magnitude and duration of afterdrop. Regardless of which rewarming protocol was followed, the esophageal site always showed the smallest afterdrop. Although there were no differences in the rewarming rates calculated for each of the three core temperature sites during inhalation and spontaneous rewarming, both auditory canal and esophageal sites rose significantly quicker than rectal during the rapid rewarming in 40 degrees C water. Inhalation rewarming led to a depressed metabolic rate, compared to spontaneous rewarming, which was not compensated by heat provided through the respiratory tract. It was concluded that for mildly hypothermic subjects, rapid rewarming in 40 degree C water was the most efficient procedure and that esophageal temperature--the closest approximation of aortic blood or cardiac temperature--is the most sensitive to change during rewarming by any procedure.(ABSTRACT TRUNCATED AT 250 WORDS)