Effect of Human Skin Grafts on Whole-Body Heat Loss During Heat Stress: A Case Study

Abstract

Studies suggest that the local heat loss responses of sweating and skin blood flow are impaired in burn survivors with skin grafts. However, it is unknown how skin grafts alter whole-body heat exchange during exercise in the heat, particularly when the skin grafts cover a significant fraction of body surface area. PURPOSE: To compare differences in whole-body heat exchange between a burn survivor in which skin grafts represent 75% of body surface area, relative to the average response of 2 control participants matched for age, body composition and fitness. METHODS: One burn survivor, 17 years post injury, and 2 control participants performed 60 min of cycling exercise at a fixed metabolic heat production rate of 400 W in a calorimeter at 35°C, ∼20% relative humidity. Whole-body heat exchange (dry and evaporative) was measured by direct calorimetry, while concurrent indirect calorimetry was used to measure metabolic rate. Core (intestinal pill) and mean skin (non-grafted of controls; grafted of burn survivor) temperatures were measured throughout. RESULTS: Rate of metabolic heat production was similar between controls and burn survivor (394 ± 3 and 419 ± 3 W respectively). However, the maximum rate of total heat loss attained by the burn survivor only represented 67% of the average value attained by controls (253 vs. 379 ± 43 W). A dry heat gain (27 ± 10 W) was observed in the control participants. In contrast, a dry heat loss to the environment was observed in the burn survivor (17 W). Nonetheless, differences in total heat loss were primarily due to a lower evaporative heat loss for the burn survivor, which only represented 53% of the average peak value attained by controls (236 vs. 406 ± 53 W). Consequently, the increase in body heat content during exercise was greater in the burn survivor (663 κJ) compared to controls (224 ± 58 κJ). This was reflected by greater increases in core (1.22°C vs. 0.61 ± 0.19°C) and mean skin (2.05°C vs. 0.48 ± 0.21°C) temperatures for the burn survivor compared to controls. CONCLUSIONS: These data suggest that burn survivors in which skin grafts represent a significant fraction of body surface area are at a greater risk of heat stress during exercise in the heat, particularly due to reduced evaporative heat loss. Supported by NIH GM068865.