The Efficacy of Various Field Based Body Cooling Methods in Reducing Core Temperature of Heat Stressed Humans

Abstract

PURPOSE: The aim of this study is to evaluate the effectiveness of various field based body-cooling systems in providing first aid to victims of heat injuries. METHODS: N = 101 male volunteers were recruited after informed consent and randomly assigned to one of the 5 cooling method groups - body cooling unit (BCU), cold gas spray (CGS), endothermic cold pack (ECP), combined method of cold gas and cold pack (COMB) and the pressured water spray (PWS). Participants exercised in the climatic chamber (35°C, 70% rH) at 5.5 km.h−1 until core temperature reached 39.5°C. The various cooling methods were then applied to reduce body temperature to 38°C. RESULTS: The cooling rate was highest with the CGS method (0. 10°C.min-1), followed by the BCU (0.096°C.min−1) and COMB (0.090°C.min−1) Methods. The PWS and ECP Methods reported lower cooling rates of 0.06°C.min−1, and 0.059°C.min−1 respectively. As the BCU was used as the reference method for the study, the CGS and COMB METHODS were found to be good alternative field cooling methods for the reduction of heat strain. As heat dissipation rates may change with different levels of heat strain, a secondary objective of the study was to determine cooling based on a stepwise model for heat dissipation, with cooling rates calculated at every 0.5°C change in core temperature. At the first 0.5°C interval, the BCU was found to have the fastest cooling rate (0.12°C.min−1). This was followed by the COMB method (0.11°C. min−1), CGS (0.09°C.min−1), PWS and CP methods (0.08°C.min−1). Statistical analysis of the differences did not reveal any significance. Cooling rates peaked in the next 0.5°C interval (39°C to 38.5°C) for all cooling methods, with the highest observed in the BCU group (0.22°C.min−1). The final 0.5°C interval in the analysis saw mean cooling rates declining for all groups, suggesting that cooling rates were beginning to plateau at core temperatures of about 38°C. CONCLUSION: The results of the study indicate that the most effective cooling method with reference to the BCU, was the CGS, followed by the COMB, PWS and CP methods. This order is consistent using both the linear and stepwise definitions of cooling rate.