BACKGROUND: The study investigated the heat strain of personnel operating in the rear cabin of a helicopter during desert-climate missions, and to what extent the strain can be mitigated by use of battery-driven ventilation vests.

METHODS: Eight men undertook 3-h simulated flight missions in desert conditions (45 degrees C, 10% humidity, solar radiation). Each subject participated in three conditions wearing helicopter flight equipment, including body armor, and either: a ventilation vest with a 3-dimensional mesh (Vent-1), a ventilation vest with a foam sheet incorporating channels to direct the air flow (Vent-2), or a T-shirt (NoVent); each mission comprised a 10-min walk, followed by sitting for 30 min, kneeling on a vibration platform for 2 h, and finally 30 min of sitting. Core temperature, heart rate, skin temperatures and heat flux, oxygen uptake, sweating rate, and subjective ratings were recorded. Evaporative capacity and thermal resistance of the garments were determined using a thermal manikin.

RESULTS: All subjects completed the NoVent and Vent-1 conditions, whereas in the Vent-2 condition, one subject finished prematurely due to heat exhaustion. The increase in core temperature was significantly (P <= 0.01) greater in Novent (0.93 degrees C) and Vent-2 (0.88 degrees C) than in Vent-1 (0.61 degrees C). Evaporative capacity was significantly higher for Vent-1 (7.8 g . min(-1)) than for NoVent (4.1 g . min(-1)) and Vent-2 (4.4 g . min(-1)).

DISCUSSION: Helicopter personnel may be at risk of heat exhaustion during desert missions. The risk can be reduced by use of a ventilation vest. However, the cooling efficacy of ventilation vests differs substantially depending on their design and ventilation concept.