Effect of acute normobaric hypoxia on peripheral sweat rate.

Peripheral sweat rate was measured to determine if acute normobaric hypoxia exerted a local inhibition on sweat gland function. It was hypothesized that peripheral sweat rate would be reduced during hypoxia, following cholinergic stimulation. Nineteen subjects (24 +/- 3 yr; 177 +/- 9 cm; 75.5 +/- 20.1 kg), 8 females and 11 males, were tested once during normobaric hypoxia, simulating an altitude of approximately 3050 m (P(O2) = 13.9%; P(B) approximately 730 mmHg), and once at sea level (200 m; P(O2) = 20.9%; P(B) approximately 730 mmHg). While seated at rest, a approximately 7-cm(2) area of the anterior forearm was stimulated using pilocarpine iontophoresis to produce localized sweating at the site. Following stimulation, sweat was collected from the area for 15 min using a Macroduct Sweat Collection System. One-way repeated measures ANOVA indicated a significantly lower sweat rate during normobaric hypoxia (4.6 +/- 2.6 g x m(-2) x min(-1)) compared to sea level (5.5 +/- 3.0 g x m(-2) x min(-1); p = 0.006). Because sweating was initiated directly at the sweat gland, thus bypassing central nervous system input, changes in sweat rate were likely due to peripheral alterations. Although these peripheral mechanisms warrant further investigation, the results of this study suggest a direct hypoxic influence on sweat gland function as evidenced by a decrease in sweat rate.