Abstract
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°C, while monitoring the auditory canal, esophageal, rectal, and skin temperatures. Results: We observed differences of a mere 0.30-0.45°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.
