Validation of Ear Canal Temperature Prediction Model for Core Temperature Monitoring

Abstract

2146 Personal heat strain monitoring would be useful in preventing heat injuries due to uncompensable heat stress that occur during exercise in the heat. Ear canal temperature (Tec) can be used as a surrogate measure of core temperature (Tc) in occupational or military settings when the use of other temperature measurement sites is less appropriate. A personal heat strain monitor device has been developed for continuous telemetric measurement of Tc through the ear canal. In an earlier study, Tec measured during exercise in the heat were compared against rectal temperature (Tre), gastrointestinal temperature (Tgi), and a commercial ear temperature (Tac) probe. Preliminary results showed Tec to be a good indicator of Tc. Correction factors were then developed to predict Tc from Tec. PURPOSE: To validate the temperature prediction model developed in an earlier study. METHODS: N = 8 volunteers performed a heat stress protocol consisting of treadmill walking (4 km·h−1, 5% gradient) in a climatic chamber (35°C dry bulb, 70% rH, 600 W·m−2 simulated solar radiation, and 2 m·s−1). Tec and Tgi were measured continuously throughout the exercise. Participants exercised for an hour or until Tgi reached 39°C, whichever was earlier. RESULTS: The mean peak temperatures recorded were Tgi = 39.06°C ± 0.17°C, and Tec = 37.97°C ± 0.32°C. The recorded Tec showed a strong positive correlation with Tgi (r = 0.72) during exercise. When the two linear prediction equations developed in the earlier study were applied: Tc = Tec + 0.81°C, and Tc = 0.795Tphm + 8.507, the mean difference between Tgi and Tec was reduced to 0.07°C and 0.02°C respectively. CONCLUSIONS: Tec and Tgi had a linear relationship, and can be used as a good indicator of Tc during exercise. Although there is a mean error between recorded Tec and Tgi due to the difference in measurement sites, a linear correction would give readings in the range that clinicians and physiologists are familiar with interpreting.