Validity of Heart Rate Derived Core Temperature Estimation During Simulated Firefighting Tasks

Abstract Rectal core temperature monitoring can mitigate heat injury but can be invasive and impractical. EQ02 + LifeMonitor is a less invasive estimation of core temperature. Therefore, the primary purpose of this study was to determine the validity of the EQ02 + LifeMonitor validity compared to rectal thermometer core temperatures. Thirteen participants completed simulated firefighting tasks with and without turn out gear, involving four rounds of a 5-minute walk on a treadmill at 2.8 mph/2.5% grade and 20 deadlifts over five minutes in heat [40.6°C; 50% humidity]. During each trial participants wore both an EQ02 + LifeMonitor and DataTherm II rectal thermometer. Devices were statistically equivalent [Δupper p < 0.001, Δlower p < 0.001] yet there was a statistically significant difference in the value (~ 0.1°C; p < 0.001).There was a significant effect of devices [p < 0.001] and time [p < 0.001], but no interaction effect [p = 0.70] on core temperature drift. Estimated core temperature was marginally different from the DataTherm II and on average overestimated core temperature. These results suggest the EQ02 + LifeMonitor may be a viable, less invasive alternative of assessing core temperature compared to rectal temperature monitoring, especially during rigorous, intermittent activities.