Optimization of Liquid Microclimate Cooling Systems: Importance of Skin Temperature

Personal protective equipment (PPE) markedly increases heat strain, reduces work performance, and increases the incidence of heat casualties. Microclimate cooling (MCC) technologies have been successfully used to alleviate heat strain and sustain performance (Pandolf et al., 1995) (Figure 1) in mounted soldiers, but cooling limitations, power and weight restrictions do not currently make this technology applicable to dismounted soldiers. Not only does the provision of substantial MCC require a large power supply, but conventional (i.e., continuous) MCC approaches can result in constriction of the cutaneous vasculature. Overcooling increases tissue insulation (It), decreases convective heat transfer from the body core, and reduces the MCC garment – to – skin (Tsk) gradient, thus theoretically reducing MCC operating efficiency (Cheuvront et al., 2003). This is particularly true when the thermal demands of the wearer are not constant. Automated control of MCC garments using various biofeedback signals have been investigated (Nyberg et al., 2001) for their potential to improve the practicality of MCC relative to changing needs in real-time, but no comparison of an automated approach to simpler and more conventional solutions for reducing heat strain had been attempted.