Limitations of temperature measurement in the aural canal with an ear mould integrated sensor

Aural canal temperature measurement using an ear mould integrated sensor (T_ac) might be a method suited for continuous non-invasive core temperature estimation in operational settings. We studied the effect of ambient temperature, wind and high intensity exercise on T_ac and its ability to predict esophageal (T_es) and rectal temperatures (T_re). Seven subjects performed a protocol of rest at 21, 10 and 30 °C, followed by exercise and recovery at 30 °C. The subjects performed the protocol twice: with and without face-wind from halfway through the 30 °C rest period. Extra auricle insulation was applied at one side. Ambient temperature changes affected T_ac significantly, while T_es and T_re remained stable. Insulating the auricle reduced but did not abolish this effect. Wind had an immediate cooling effect on T_ac independent of auricle insulation. During exercise and recovery in 30 °C, T_ac provided acceptable group predictions of T_re in trials without wind (bias: −0.66 ± 0.21 °C covered, −1.20 ± 0.15 °C uncovered). Bias was considerably higher with wind, but variability was similar (−1.73 ± 0.11 °C covered, −2.49 ± 0.04 °C uncovered). Individual predictions of T_es and T_re showed more variation, especially with wind. We conclude that T_ac may be used for core temperature assessment of groups in warm and stable conditions