Efficiency of three cooling methods for hyperthermic military personnel linked to water availability

Purpose: Three feasible cooling methods for treatment of hyperthermic individuals in the military, that differed considerably in water volume needed (none to ~80 L), were evaluated. Methods: Ten male soldiers were cooled following exercise-induced hyperthermia (rectal temperature (T_re) ∼39.5 °C) using ventilation by fanning (1.7 m s⁻¹), ventilation by fanning (1.7 m s⁻¹) while wearing a wet t-shirt (250 mL–27 °C water) and tarp assisted cooling with oscillations (80 L of 27.2 ± 0.5 °C water; TACO). Results: Cooling rates were higher using TACO (0.116 ± 0.032 °C min⁻¹) compared to ventilation (0.065 ± 0.011 °C min⁻¹, P<0.001) and ventilation in combination with a wet t-shirt (0.074 ± 0.020 °C min⁻¹, P=0.002). Time to cool (TTC) to T_re=38.2 °C for TACO was shorter (14 ± 4 min) compared to ventilation only (20 ± 5 min; P=0.018), but not to ventilation while wearing a wet t-shirt (18 ± 6 min; P=0.090). Conclusions: TACO may be an acceptable, efficient and feasible cooling method in case of exertional heat stroke. However, in case of limited water availability, transportat should be prioritized, and cooling of any form should be implemented while waiting for and during transport.