Effects of topical skin protectant on heat exchange in humans

The application of a Topical Skin Protectant (TSP) under chemical protective clothing may impair heat exchange and/or decrease tolerance time during exercise.

The extent to which TSP might act as a barrier to heat transfer was unknown. Since TSP may be permeable to water vapor, we hypothesized that there would be no significant differences between treatments on variables effecting heat exchange.

There were 10 subjects who walked (3.5 mph, 3% grade) until volitional exhaustion in an environmental chamber (TA = 36.0 +/- 0.5 degrees C; TDP = 27.0 +/- 1.0 degrees C) in two conditions: no TSP application (CON) and TSP application (TSP). TSP was applied to 21% of body surface area on six specific areas. Esophageal temperature, skin temperature (8 sites), heart rate, and pre- and post-experimental weights were measured. Mean skin temperature, mean body temperature, changes in esophageal temperature per min of exercise, evaporative heat loss, and sweating rate were calculated.

There was no effect (p < 0.05) of TSP on esophageal temperature, mean skin temperature, heart rate, tolerance time (CON: 139.3 +/- 32.5 vs. TSP: 132.3 +/- 37.0 min), sweating rate (CON: 9.5 +/- 1.9 vs. TSP: 9.4 +/- 3.03 g.min-1) and evaporative heat loss (CON: 200.9 +/- 31.6 vs. TSP: 215.9 +/- 25.9 W.m-2). The change in TES per min of exercise averaged 0.014 +/- 0.003 degree C during TSP and 0.012 +/- 0.003 degree C during CON, and was higher (p = 0.024) in TSP. At this rate, the difference between treatments for 4 h would be 0.48 degree C. There were no adverse local or systemic reactions to TSP application.

TSP application minimally affected heat exchange under the conditions of this study.