Thermal increment provided by inhalation rewarming from hypothermia.

To quantify the core temperature gain derived from inhalation rewarming, 10 subjects were immersed in seawater (mean temperature 12 degrees C) until a 2 degree C drop in rectal temperature occurred, and were then rewarmed by breathing hot saturated air at 45 degrees C for 30 min. Each subject was rewarmed once breathing air and once rebreathing a controlled fraction of expired air adjusted to produce a hyperventilation of 50 l/min. After 30 min of rewarming mean rectal temperature had increased 0.39 degrees C in subjects breathing air compared with 0.77 degrees C in those hyperventilating (P less than 0.01). Corresponding gains in tympanic temperatures were 1.1 and 1.5 degrees C, respectively. Calculations indicate that the additional heat input with hyperventilation yielded a core (rectal) temperature gain of 5.1 X 10(-4) degrees C/l. It is concluded that each additional 10 l/min of ventilation of hot saturated air will increase the rate of core rewarming from hypothermia by approximately 0.3 degrees C/h.