A multi-sensor wearable system based on FBG technology: Analysis of the influence of measurement sites on systems performance in cardiorespiratory monitoring

Wearable systems are considered one of the most promising advanced digital healthcare technologies usable for the continuous monitoring of vital signs and enhancing long-term care. In this paper, we proposed a multi-sensor wearable sensing solution for respiratory (RR) and heart rate (HR) estimation via strain sensing. The system consists of two fiber Bragg gratings (FBGs) encapsulated within flexible substrates and positioned at two different body locations (i.e., the neck and left sternum). A finite element model was proposed to motivate the sensors’ shape showing that this design increases the FBG measurement range without any risk of breakage. A metrological assessment was carried out to evaluate the sensors’ strain sensitivity, measurement uncertainty, and hysteresis error. Finally, the multi-sensor approach enabled the simultaneous investigation of the system capability of monitoring RR and HR from the two mentioned body locations for assessing the measurement site impact on the system performance.