Infrared tympanic thermometry in a hot environment.

The purpose of this study was to compare tympanic (measured by infrared thermometry; Tty- (IRED)) with rectal and esophageal temperatures (T(REC) and T(ES)) during exercise in the heat. During Experiment 1, nine subjects pedaled for 55 min in a hot-dry environment (37 degrees C; 27% humidity) in still-air (<0.2 m/s) and for 10 additional min using water ingestion, wind and ice to cool them down. During Experiment 2, subjects pedaled for 90 min in a similar environment but with airflow at 2.5 m/s. Pearson correlation coefficients (r) and Bland-Altman plots were calculated. In Experiment 1, Tty-(IRED) and T (REC) were highly correlated (r=0.83; p<0.001) with close agreement (-0.08+/-0.4 degrees C). Overall Tty-(IRED) was significantly correlated with T(ES) (r=0.91; p<0.001). Cold water ingestion did not affect Tty-(IRED) or T(REC) but lowered T(ES). Wind and ice application lowered Tty- (IRED) below T(REC) (p<0.05). During Experiment 2, Tty-(IRED) was lower than T(REC) (p<0.05) and the difference increased throughout exercise as hyperthermia developed resulting in low agreement (-1.01+/-1.1 degrees C). In conclusion, Tty- (IRED) dangerously underestimates T(REC) when exercising in a hot environment with airflow or during a cooling treatment. However, it could correctly detect hyperthermia during exercise in a hot still-air environment.