Cadarette Bruce S, Levine Leslie, Kolka Margaret A, Proulx Gary N, Correa Mathew M, Sawka Michael N
U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
Aviat Space Environ Med. 2002 Jul;73(7):665-72.
The purpose of this study was to compare a vapor compression microclimate cooling system (MCC) and a personal ice cooling system (PIC) for their effectiveness in reducing physiological strain when used with cooling garments worn under the impermeable self-contained toxic environment protective outfit (STEPO). A second comparison was done between the use of total body (TOTAL) and hooded shirt-only (SHIRT) cooling garments with both the MCC and PIC systems. It was hypothesized that the cooling systems would be equally effective, and total body cooling would allow 4 h of physical work in the heat while wearing STEPO.
Eight subjects (six men, two women) attempted four experiments at 38 degrees C (100 degrees F), 30% rh, 0.9 m x sec(-1) wind, while wearing the STEPO. Subjects attempted 4 h of treadmill walking (rest/exercise cycles of 10/20 min) at a time-weighted metabolic rate of 303 +/- 50 W.
Exposure time was not different between MCC and PIC, but exposure time was greater with TOTAL (131 +/- 66 min) than with SHIRT (83 +/- 27 min) for both cooling systems (p < 0.05). Cooling rate was not different between MCC and PIC, but cooling rate while wearing TOTAL (362 +/- 52 W) was greater than with SHIRT (281 +/- 48 W) (p < 0.05). Average heat storage was lower with MCC (39 +/- 20 W x m(-2)) than with PIC (50 +/- 17 W x m(-2)) in both TOTAL and SHIRT (p < 0.05). Also, average heat storage while wearing TOTAL (34 +/- 19 W x m(-2)) was less than with SHIRT (55 +/- 13 W x m(-2)) for both cooling systems (p < 0.05). The Physiological Strain Index (PSI) was lower in MCC-TOTAL (2.4) than MCC-SHIRT (3.7), PIC-SHIRT (3.8), and PIC-TOTAL (3.3) after 45 min of heat exposure (p < 0.05).
Total body circulating liquid cooling was more effective than shirt-only cooling under the impermeable STEPO uniform, providing a greater cooling rate, allowing longer exposure time, and reducing the rate of heat storage. The MCC and PIC systems were equally effective during heat exposure, but neither system could extend exposure for the 4 h targeted time.
本研究的目的是比较蒸汽压缩微气候冷却系统（MCC）和个人冰冷却系统（PIC）在与不透水的自给式有毒环境防护服（STEPO）下穿着的冷却服装一起使用时，在减轻生理应激方面的有效性。还对MCC和PIC系统使用全身（TOTAL）冷却服装和仅带帽衬衫（SHIRT）冷却服装进行了第二次比较。假设冷却系统将同样有效，并且全身冷却将允许在穿着STEPO的情况下在高温环境中进行4小时的体力劳动。
八名受试者（六名男性，两名女性）在38摄氏度（100华氏度）、30%相对湿度、0.9米/秒风速的条件下，穿着STEPO尝试进行四项实验。受试者以303±50瓦的时间加权代谢率进行4小时的跑步机行走（休息/运动周期为10/20分钟）。
MCC和PIC之间的暴露时间没有差异，但对于两种冷却系统，TOTAL（131±66分钟）的暴露时间比SHIRT（83±27分钟）更长（p<0.05）。MCC和PIC之间的冷却速率没有差异，但穿着TOTAL时的冷却速率（362±52瓦）大于穿着SHIRT时的冷却速率（281±48瓦）（p<0.05）。在TOTAL和SHIRT中，MCC的平均蓄热量（39±20瓦·平方米⁻²）低于PIC（50±17瓦·平方米⁻²）（p<0.05）。此外，对于两种冷却系统，穿着TOTAL时的平均蓄热量（34±19瓦·平方米⁻²）低于穿着SHIRT时的平均蓄热量（55±13瓦·平方米⁻²）（p<0.05）。热暴露45分钟后，MCC-TOTAL组的生理应激指数（PSI）（2.4）低于MCC-SHIRT组（3.7）、PIC-SHIRT组（3.8）和PIC-TOTAL组（3.3）（p<0.05）。
在不透水的STEPO制服下，全身循环液体冷却比仅衬衫冷却更有效，提供更高的冷却速率，允许更长的暴露时间，并降低蓄热速率。在热暴露期间，MCC和PIC系统同样有效，但两种系统都不能将暴露时间延长至目标的4小时。
