A Comparative Study of Two Ambulatory Core Temperature Assessment Methods

Background. Given the need to identify reliable non-invasive solutions for core temperature ambulatory monitoring, the purpose of this study was to evaluate the performance of zero-heat-flux (ZHF) temperature sensor on the forehead ($T_{\mathrm{COzhf}}$) by comparing it with intestinal temperature ($T_{\mathrm{COpill}}$) in different ambient and physiological conditions.Methods. Seven trained male subjects were followed during a 45-min rest period (STA) and a 25-min self-regulated cycling exercise performed in neutral (TMP, 22.8?°C) and hot (HOT, 38.5 °C) ambient temperature.Results.$T_{\mathrm{COzhf}}$ values differed from $T_{\mathrm{COpill}}$ of ?0.23 ± 0.13 in STA, 0.15 ± 0.30 °C in TMP and $0.28\pm 0.38$?°C in HOT. The 95% limits of agreement showed an acceptable bias between $T_{\mathrm{COzhf}}$ and $T_{\mathrm{COpill}}$ in STA (±0.26?°C), but not in TMP and HOT (±0.60 and ±0.75?°C).Conclusion. The non-invasive ZHF sensor gave an accurate estimation of $T_{\mathrm{COpill}}$ in steady state but not during exercise. However, complementary results let suppose that ZHF performance is not affected by ambient conditions and could be a relevant alternative for deep body temperature measurement during whole-body heat stress.