Technique for continuously monitoring core body temperatures to prevent heat stress disorders in workers engaged in physical labor.

OBJECTIVES: Measuring core body temperature is crucial for preventing heat stress disorders in workers. We developed a method for measuring auditory canal temperatures based on a thermocouple inserted into a sponge-type earplug. We verified that the tip of this thermocouple is positioned safely, allowing the wearer to engage in normal physical tasks; this position averaged 6.6 mm from the tympanic membrane. METHODS: To assess this technique, we had six healthy male students repeat three cycles of exercise and rest (20 min of exercise and 15 min of rest) in a temperature-controlled chamber with temperatures set at 25, 30, or 35 degrees C, while monitoring the auditory canal, esophageal, rectal, and skin temperatures. RESULTS: We observed differences of a mere 0.30-0.45 degrees C between rectal temperatures and auditory canal temperatures measured with the thermocouple, the smallest such difference reported to date in studies involving auditory canal temperature measurement. CONCLUSIONS: We conclude that monitoring temperatures based on a technique involving an auditory canal plug can be used to estimate rectal temperatures accurately, and thereby to avoid conditions leading to heat stress disorders.

[Body cooling capacity of water circulated cooling pants during lower body exercise in a hot environment].

We investigated the body cooling capacity of water-circulated cooling pants during lower body exercise in a hot environment. Five subjects were asked to ride a bicycle ergometer and to keep a work rate of 75 W continuously for 20 minutes. They then rest on the ergometer for 15 minutes, in a climate chamber kept at WBGT = 31.5 degrees C. They repeated the same procedure three times under three different conditions; 1) wearing cooling pants with cold water supply; 2) wearing cooling pants without water supply; 3) wearing short pants instead of cooling pants. Esophageal temperature and heart rate of the subjects, when their cooling pants were supplied with cold water, were lower compared with the condition without water supply, and were almost the same as the condition wearing short pants. Water-circulated cooling pants should effectively cool the body at work where the worker has to wear pants that cover his legs to prevent injury.