Physiological strain of next generation combat uniforms with chemical and biological protection: importance of clothing vents.

This study examined whether vents in the arms, legs and chest of new protective assault uniforms (PTAU) reduced heat strain at 35 °C during a low dressed state (DSlow), and subsequently improved tolerance time (TT) after transitioning to DShigh compared with the battle dress uniform and overgarment (BDU+O). Small but significant reductions in rectal temperature (Tre), heart rate and vapour pressures over the thigh and shin were observed during DSlow with vents open (37.9 ± 0.2 °C, 120 ± 10 b/min, 3.7 ± 0.4 and 3.5 ± 1.0 kPa) versus closed (38.0 ± 0.1 °C, 127 ± 5 b/min, 4.3 ± 0.3 and 4.6 ± 0.5 kPa). During DShigh Tre was reduced and TT increased significantly with the PTAUs (1.1 ± 0.2 °C/h and 46 ± 24 min) versus BDU+O (1.6 ± 0.2 °C/h and 33 ± 16 min). The vents marginally reduced heat strain during DSlow and extended TT during DShigh) compared with BDU+O. Practitioner Summary: Clothing vents in chemical and biological protective uniforms can assist with heat transfer in situations where the uniforms must be worn for extended periods prior to exposure to a hazardous condition. Once the vents are closed, exposure time is increased and the increase in body temperature reduced.