Prediction of rectal temperature from ear canal temperature

Abstract

Personal heat strain monitoring provides the best means for maximizing worker safety and productivity in hot jobs. The present study compared methods for reducing the environmental effect on aural canal temperature in an attempt to reduce the predictive error of a personal heat stress monitor (QST) and a simple ear thermistor (EAR). Subjects underwent three exposures in impermeable protective clothing (PC) in an environment of 30.1 degrees C wet bulb globe temperature (WBGT) wearing either ear plugs (PLG), ear moulds (MLD) or ear moulds and earmuffs (MFS). Mean work time across all trials was 63.1 +/- 7.9 min, with a mean rectal temperature at 60 min of 38.5 +/- 0.1 degrees C and a sweat production rate of 29.7 +/- 8.6 g/min. Rectal temperature was used as the criterion measure of core temperature. Although group mean predictions were satisfactory, large SD of mean differences (+/- 0.36) meant that predictive ability of QST for individuals was greatly impaired. A simple well-insulated ear thermistor showed slightly better accuracy (+/- 0.28) as a predictor of rectal temperature across time, particularly at peak temperatures. Incorporating the predictive error of aural temperature still extended the duration of safe work times relative to ACGIH guidelines. Further investigation is still necessary to ensure that predictions based on aural temperature are accurate and safe for the worker population across varying conditions.

Technique for Continuously Monitoring Core Body Temperatures to Prevent Heat Stress Disorders in Workers Engaged in Physical Labor

“…The only article evaluating the use of auditory canal temperatures in actual workplace settings concludes that the method was a poor index of core temperature; however, that report failed to report the precise positioning of the thermocouple 10) . Muir et al used infrared sensors to measure auditory canal temperatures and observed differences from rectal temperatures exceeding 0.6°C, but failed to verify the location of the sensor 4) . Some studies have placed the thermocouple within a few millimeters of the tympanic membrane.…”

Hearables: New Perspectives and Pitfalls of In-Ear Devices for Physiological Monitoring. A Scoping Review

“…Increasing the accuracy of measurements may rely on the improvement of signal/data acquisition and device stability, potentially through the implementation of new materials, as exemplified by graphene-coated T sensors (Chaglla et al, 2018 ). Probe development for T measurement should pursue personalization to adapt the device to the specific anatomy of each user (Muir et al, 2001 ; Venema et al, 2012 ; Ota et al, 2017 ), allowing a better insulation from external conditions (Teunissen et al, 2011 ; Strapazzon et al, 2015 ). For PPG-based measurements, accuracy may be improved by optimizing sensor design and wavelength [e.g., optimal LED-photodiode distance, shunt-light reduction (Buschmann and Huang, 2010 )], but also by developing suitable signal processing and advanced algorithms for noise removal (Poh et al, 2010 ; Poh and Kittler, 2012 ; Tomita et al, 2018 ).…”

Accuracy of Tympanic Temperature Measurement in Firefighters Completing a Simulated Structural Firefighting Task

“…Alternatively, insulating the auditory canal from the environment is likely to limit the temperature gradient drastically within the auditory canal, 29 permitting improved measurement accuracy through use of a tympanic probe. 30 While Pryor et al 26 reported that tympanic probes were more erroneous than infrared tympanic monitors, the precise location of the probe was not detailed and the auditory canal was not insulated in that study.…”