The Effect Of Burn Location On Internal Body Temperature Responses During Exercise In The Heat

Abstract

According to the US Army’s Standard of Medical Fitness (AR 40-501), extensive burn injuries will disqualify individuals from US Army service, depending in part on the anatomic location of the injury. Specifically, these guidelines state that “extensive burns on the torso will most significantly impair heat dissipation.” and that burn injuries could be a disqualifying criteria for continued service. However, the effects of the location of the burn injury on thermoregulation during exercise is currently unknown. PURPOSE: This study tested the hypothesis that a torso burn injury is not any more detrimental to whole-body heat dissipation relative to a similar sized non-torso burn injury. METHODS: Nine healthy subjects (29±6 years; 72.44±11.29 kg; 1.86±0.17 m2) walked on a treadmill (~3.3mph) in the heat (40 °C and 20% relative humidity) for 60 minutes at a fixed rate of metabolic heat generation (5.7±0.5 W/kg). Identical ~25% body surface area (BSA) burn injuries to the torso or non-torso extremities (randomized) were simulated by applying a highly absorbent vapor-impermeable material over those regions. The elevation in internal body temperature assessed via an ingestible telemetry pill, was the primary variable of interest. Additional analyses were performed to assess differences in heart rate and thermal sensation. RESULTS: The statistical model (2 way repeated measures ANOVA) identified a main effect of time (p<0.001; 0.94±0.33 °C for torso and 0.91±0.34°C for extremity at end of exercise) on the increase in internal body temperature, with no effect of simulated burn location (p=0.76) or interaction (p=0.10). Heart rate and thermal sensation showed similar responses, with a significant main effect of time (p<0.001) with no effect of burn location (p=0.09) or interaction (p=0.13). CONCLUSION: Contrary to the Army’s guidelines, these results suggest that torso burns do not limit heat dissipation and exacerbate thermal strain compared to non-torso burn injuries. Therefore, the Army should not consider torso burns as being more detrimental when determining whether a soldier meets the Standard of Medical Fitness. Funding: Department of Defense - US Army W81XWH-15-1-0647