Evaluation of non-invasive sensors for monitoring core temperature.

Abstract

We evaluated the accuracy and precision of zero-heat flux (ZHF) and dual sensor (DS) non-invasive temperature probes in intensive care unit (ICU) patients undergoing hypothermic temperature control, hypothesizing that both devices would accurately estimate core temperature. In a single-center prospective cohort study, we enrolled 35 ICU patients and applied continuous, non-invasive ZHF and/or DS probes to the lateral forehead or anterior chest to collect 358 observations. Conditions potentially influencing temperature estimation were recorded. Using Bland-Altman analysis with multiple paired observations per individual, we compared the bias between non-invasive probes and direct core temperature measurements. Lin's concordance coefficient (LCC) was computed to quantify precision. The mean bias between the ZHF probe and invasive temperature was + 0.98 °C; for the DS probe, it was - 2.19 °C. In hypothermic patients, the ZHF probe's accuracy improved (bias + 0.28 °C, LCC 0.86), while the DS probe remained inaccurate (bias - 2.52 °C, LCC 0.07). Clinical confounders like vasoactive agents or temperature control devices did not consistently affect bias, accuracy, or precision. Neither the ZHF nor DS non-invasive probes provided sufficient accuracy or precision to guide clinical decisions in the ICU. These results contrast with previous studies reporting biases within ± 0.5 °C. However, the ZHF probe showed promising limited deviation, especially in hypothermic patients.