A homecare in-bed hardware system for precise real-time ECG and HRV monitoring with layered clothing.

Continuous monitoring of heart activity, particularly electrocardiogram (ECG) waveforms and heart rate variability (HRV), is essential for the early detection of cardiac diseases. However, conventional wearable ECG systems typically require direct skin contact and external software for signal acquisition and analysis, limiting user comfort and long-term usability. This study presents an unobtrusive contactless bed-embedded system that enables wearable-free, comfortable, and precise monitoring of ECG and HRV without the need for the subject to undress. Flexible active electrodes achieve high signal acquisition performance and strong noise immunity by employing double active shielding for noise reduction of 64 dB. The analog front-end has an input-referred noise of 0.49 μV within the QRS bandwidth. Further noise reduction of 27.5 dB is obtained by a non-contact driven-right-leg. Real-time signal denoising, R-peak detection, and HRV calculation are performed on the field-programmable gate array for on-hardware processing, running a stationary wavelet transform and adaptive thresholding. The system demonstrates over 70% R-peak detection precision for users wearing even thick clothing during a 5-minute measurement. This system enables R-peak detection when the subject makes slight movements.