Segmented-Beat Modulation Method-Based Procedure for Extraction of Electrocardiogram-Derived Respiration from Data Acquired by Wearable Sensors During High-Altitude Activity.

High-altitude sports are affected by hypoxic stress-related alterations and, consequently, may trigger severe events such as sport-related sudden death; thus, into-the-jield monitoring of respiration is essential. A Segmented-Beat Modulation Method (SBMM)-based procedure was previously proposed to extract electrocardiogram $(ECG)$ - derived respiration $(EDR)$ . The aim of this study is to validate SBMM-based procedure for $EDR$ extraction in data acquired by wearable sensors during high-altitude physical activities. Respiration signal $(RES)$ and $ECG$ were recorded using BioHarness 3.0 by Zephyr from 3 expeditioners, while performing a trek up to 4, $556m$ of altitude. $EDR{\it was}$ extracted from $ECG$ by SBMM-based procedure. $RES$ and $EDR$ were segmented into 60-second windows and characterized in terms of breathing rate ( $BR_{RES}$ and $BR_{EDR}$ , respectively). $BR_{RES}$ and $BR_{EDR}$ were compared by absolute difference $(\vert \delta\vert)$ , concordance correlation coefficient $(CCC)$ and linear regression analysis. Results confirmed $EDR$ goodness, proved by low values of $\vert \delta\vert (2[1;4]cpm)$ , satisfactory $CCC(0.62$ ; P-value $< 0.05$ ) and good fit of regression line $(BR_{RES}=0.91\cdot BR_{EDR}+4.47cpm)$ . In conclusion, SBMM-based procedure is a good method to extract $EDR$ from data acquired by wearable sensors during high-altitude physical activities.