Effect of isolated head heating and cooling on sweating in man.

A double climate chamber which permitted the independent regulation of temperature in each chamber was used to produce isolated head heating and cooling in three subjects. Deep body temperature was recorded from the tympanic membrane, oral cavity, esophagus, and rectum. Skin temperature was measured on nine body regions and a weighted mean skin temperature was calculated. Sweating rate was measured by resistance hygrometry from six regions. When head skin temperature was increased, deep body temperature measured at the tympanic membrane and oral cavity increased more than esophageal temperature, while rectal temperature remained essentially unchanged. Sweating rate increased when head skin temperature increased and again, somewhat later, as the tympanic membrane and oral temperatures began to rise. When head skin temperature was decreased, tympanic membrane and oral temperatures decreased and sweating again followed the changes in skin temperature as well as the changes in tympanic membrane and oral temperatures. Since it has been shown that head skin temperature is particularly important in determining thermal comfort and sweating rate when compared to other body regions, it is suggested that this particular sensitivity is in part due to a thermal counter-current exchange between venous blood draining the head and arterial blood ascending to intracranial thermoreceptors. Such an exchange would correspond to similar mechanisms present in other species.