Combining unobtrusive electrocardiography and ballistography for more accurate monitoring of sleep

We propose an unobtrusive bed integrated system for monitoring physiological parameters during sleep. Our system uses textile electrodes attached on the bed sheet for measuring multiple channels of electrocardiogram from which one at a time is selected for RR-interval detection and force sensors located under a bed post for detecting breathing and movements. The movement information is also used to assist in heart rate detection. We tested the system with six subjects in one hour recordings and achieved an average of 94 % detection coverage and 99 percentile absolute error of 2.86 ms for the RR-interval signal. Mean absolute error of the detected respiration cycle lengths was 0.24 seconds.