Infrared Thermometry in the Diagnosis and Treatment of Heat Exhaustion

Infrared (IR) thermometers (FirstTemp 2000A, Intelligent Medical Systems, California) were used to monitor tympanic temperature (T_ty) in 12 collapsed fun-runners suspected of suffering exertion-induced heat exhaustion (EIHE). Rectal temperature (T_re) was monitored via digital clinical thermometers. Conditions during the fun-run and in the field treatment centre were cool (air temperature 16 - 18 °C, relative humidity 60 - 65 %). On admission, T_ty was (mean ± SEM) 1.2 ± 0.3 °C lower than T_re. For admission plus subsequent monitoring data pooled, although T_ty correlated significantly with T_re (r = 0.86, p < 0.001), mean T_ty (37.4 ± 0.2 °C) was significantly lower (p < 0.01) than mean Tre (38.4 ± 0.4 °C). Cotton wool ear pads, applied to 10 of the runners on admission to minimise environmental effects on T_ty, did not significantly improve the IR monitoring. A T_ty ≥ 37.1 °C predicted a T_re ≥ 38 °C (an established diagnostic criterion for EIHE) with a sensitivity of 0.93 and a specificity of 0.63. These data indicate that IR tympanic thermometry, when utilised in cool environments, can result in misdiagnosis of heat exhaustion. Although IR thermometry shows some promise as a rapid, non-invasive means of monitoring core temperature, it should not be used in the diagnosis and treatment of heat exhaustion unless further research validates the method.

Key words

Diagnosis - heat exhaustion - infrared thermometry - tympanic temperature