Monitoring workers wearing protective clothing in a hot environment and methods of rapid cooling.

摘要

Workers in protective clothing (PC), including military personnel and athletes, generate metabolic heat in environments which interfere with heat dissipation. As heat injuries can occur quickly in these circumstances assessing the heat stress, monitoring responses, and treating any injuries promptly is of great importance. This investigation examined the micro-enviromnent produced by PC, the use of aural canal temperature for monitoring heat strain, and three methods of cooling subjects with high exertional heat storage. Subjects (n = 15) underwent three work trials in impermeable PC in an environment of 30°C (WBGT). Subjects (n = 15) underwent three work trials in impermeable PC in an environment of 30°C (WBGT). Mean work time across all trials was 63 +/- 8 min, with a mean rectal temperature at 60 minutes of 38.5 +/- 0.1°C, and sweat production rate of 30 +/- 9 g·min --1. Micro-environmental temperature increased over the duration of each work period to a mean micro-environmental WBGT of 34.6°C, and vapor pressure of 5.4 kPa (relative humidity 92%). At this particular ambient temperature, an adjustment factor of 5°C WBGT would give a more accurate indication of thermal stress than current clothing adjustment factors, for up to 1 hour of continuous moderate work. Prediction of rectal temperature from aural canal temperature showed the duration of safe work times could be extended by almost 300%. A simple well insulated ear thermistor showed slightly better accuracy as a predictor of rectal temperature across time than a commercially available personal monitor. In the last study, three types of treatment were used to cool subjects (n = 10). Immersing the torso-only in ice water produced a comparable cooling rate (0.10 +/- 0.03°C·min --1) to whole body immersion (0.13 +/- 0.04°C·min --1). The cooling rate of a water-perfused. vest and hood (0.03 +/- .01°C·min--1) did not match those of immersion, but might be used as a field emergency treatment. These cooling rates are comparable to those reported for heatstroke patients suggesting that this model is a useful means for testing the effectiveness of heatstroke treatments.