• David Hostler, Joe Suyama, Riana R Pryor, Steven E Reis, and Thirimachos Bourlai.
• Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, West Virginia, USA.
• Prehosp Emerg Care. 2012 Jul 1;16(3):390-9.

BackgroundMonitoring core body temperature to identify heat stress in first responders and in individuals participating in mass gatherings (e.g., marathons) is difficult.ObjectiveThis study utilized high-sensitivity thermal imaging technology to predict the core temperature of human subjects at a distance while performing simulated field operations wearing thermal protective garments.MethodsSix male subjects participating in a study of precooling prior to exertion in wildland firefighter thermal protective clothing had thermal images of the face captured with a high-resolution thermal imaging camera concomitant with measures of core and skin temperature before, during, and after treadmill exercise in a heated room. Correlations and measures of agreement between core temperature and thermal imaging-based temperature were performed.ResultsThe subjects walked an average (± standard deviation) of 42.6 (±5.9) minutes and a distance of 4.2 (±0.6) km on the treadmill. Mean heart rate at the end of exercise was 152 (±33) bpm and core body temperature at the end of exercise was 38.3°C (±0.7°C). A visual relationship and a strong correlation between core temperature and thermal imaging of the face were identified in all subjects, with the closest relationship and best agreement occurring during exercise. The Bland-Altman test of agreement during exercise revealed the majority of measurement pairs to be within two standard deviations of the measured temperature.ConclusionsHigh-resolution thermal imaging in the middle-wave infrared spectrum (3-5 μm) can be used to accurately estimate core body temperature during exertion in a hot room while participants are wearing wildland firefighting garments. Although this technology is promising, it must be refined. Using alternative measurement sites such as the skin over the carotid artery, using multiple measurement sites, or adding pulse detection may improve the estimation of body temperature by thermal imagery.

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