Wearable sensor-derived heart rate variability (LF/HF): a promising biomarker for predicting inadvertent perioperative hypothermia.

Inadvertent perioperative hypothermia (IPH) is a common perioperative complication in developing countries, and effective assessment tools for IPH risk stratification are still needed in these regions. In this letter, we report a validated mobile phone app-based heart rate variability (HRV) analysis procedure used in 220 adult patients scheduled for abdominal surgery to explore the relationship between preoperative 5-minute HRV metrics and IPH. Multivariate logistic regression analysis identified the HRV metric-the ratio of low-to high-frequency power (LF/HF)-as superior to previously reported clinical IPH predictors. For the outcomes of IPH within the first 30 minutes and 1 hour of surgery, receiver operating characteristic curves for regression models including both baseline core temperature and LF/HF showed area under the curve values of 0.96 (95% confidence interval, 0.93-0.98) and 0.92 (95% confidence interval, 0.87-0.96), respectively. Our results suggest that the HRV metric LF/HF, generated via a wearable sensor during patients' 5-minute preoperative adaptation to the operating room ambient temperature (22°C-23°C), may serve as a promising biomarker for IPH in future research.