A wearable cardiorespiratory sensor system for analyzing the sleep condition

This paper describes a long-term cardiorespiratory sensor system, which is supposed to be used for monitoring sleep condition at home environment. This system consists of belt sensor probe, data acquisition and communication devices, and the data processing algorithms. New wearable sensor probe with a couple of conductive fabric sheets material and a PVDF film material is developed. To obtain clear cardiorespiratory responses from the belt sensor probe, adaptive hardware filters with signal conditioners are designed and further software data processing algorithms are proposed for extraction of the relative cardiorespiratory information, such as respiratory cycle (RC) and RR interval (RRI). These simple and powerful data processing algorithms for extraction of the proposed RC and RRI information are described and testified in detail. And two commercial sensor devices such as thermistor-type pneumography sensor and 3-lead electrocardiogram sensor are used simultaneously to validate the performance and efficiency of the proposed sensor system. Furthermore, the belt type sensor demonstrated that PVDF film and conductive fabric sensors can complement each other, especially in RRI extraction. Finally, for a case study, the sleep conditions are estimated experimentally by analyzing the heart rate variability (HRV) from the extracted RRI information.