Thermoregulatory adjustments to thermal transients during slow wave sleep and REM sleep in man

The present study was performed on five nude male subjects by increasing the ambient temperature during well-established slow wave sleep (SWS) and rapid eye movement (REM) sleep episodes. 1. Air temperature was raised from 25 to 41 degrees C at rates of + 0.8 degrees C.min-1 or + 1.6 degrees C min-1 and, afterwards, was maintained at 41 degrees C during 10 min before returning to the initial pre-heating condition. During these thermal transients, wall temperatures (Tw), dew-point temperature (Tdp) and air velocity (Va) were kept constant (Tw = 37.5 degrees C; Tdp = 10 degrees C; Va = 0.3 m.s.-1). Physiological data included 3 EEGs, 2 EOGs, 4 EMGs, heart rate, finger pulse amplitude, esophageal temperature and 10 local skin temperatures. Upper chest sweating rate was recorded by a 12 cm2-capsule using a dew-point hygrometer technique. 2. The results showed that during REM sleep sweat gland activity persists at a lower level than during SWS. The lower sensitivity of the thermoregulatory system described during the REM sleep episodes could be interpreted by an increase of the hypothalamic set-point temperature, or by an action of extra-hypothalamic thermosensitive neurons. However, a change at the sweat gland level cannot be ruled out.