Inhalation of warm and cold air does not influence brain stem or core temperature in normothermic humans

The present study tested the hypothesis that inhalation rewarming provides a thermal increment to central neural structures adjacent to the nasopharyngeal region. Auditory-evoked brain stem responses of 14 subjects (7 men and 7 women) were monitored for 25 min while they inspired room air (24 degrees C) followed by hot air (41 degrees C) saturated with water vapor and cold dry air (-1 degrees C). The latencies of peaks I, III, and V and the interpeak latencies (IPLs) I-III, III-V, and I-V were compared among the three conditions with a repeated-measures ANOVA. Changes in IPLs are sensitive markers of changes in brain stem temperature. Tympanic temperature (T(ty)) was measured with an infrared tympanic thermometer. There were no significant differences in T(ty), peak latencies I, III, and V, and IPLs I-III, III-V, and I-V. The results indicate that inhalation of hot and cold air does not influence T(ty), nor does it influence the temperature of the brain stem. We conclude that inhalation rewarming is not capable of warming the vital central neural structures adjacent to the naropharynx.