Multi-channel optical sensor-array for measuring ballistocardiograms and respiratory activity in bed

Abstract

Abstract-Our work covers improvements in sensors and signal processing for unobtrusive, long-term monitoring of cardiac (and respiratory) rhythms using only non-invasive vibration sensors. We describe a system for the unobtrusive monitoring of vital signs by means of an array of novel optical ballistocardiography (BCG) sensors placed underneath a regular bed mattress. Furthermore, we analyze the systems spacial sensitivity and present proof-of-concept results comparing our system to a more conventional BCG system based on a single electromechanical-film (EMFi) sensor. Our results suggest that the proposed optical multi-channel system might be used to reduce beat-to-beat heart rate estimation errors, as well as enable the analysis of more complex breathing patterns.

Ambient and Unobtrusive Cardiorespiratory Monitoring Techniques

“…The use of load-cells located under bed posts [34], [35] or as part of a weighing scale [36] has also been proposed. Optical methods for measuring BCG include the deformation of optical fibers in a mattress [37], [38] and the scattering of IR light inside the mattress foam itself [39] or in mattress cavities [40], [41]. Further concepts include the use of accelerometers in a mattress topper [42], ultrasound sensors to measure the deformation of a plate mounted underneath a mattress [43], strain gauges to detect deformations of slats in a bed frame [16], proprietary pressure pads [44], or conductive fibers woven into a mattress itself [45].…”

Respiration Detection Chip With Integrated Temperature-Insensitive MEMS Sensors and CMOS Signal Processing Circuits

“…10, caused by a single nozzle jet was approximately 2, 15, and 35 mV for the three sensing structures, respectively. In addition, because two micro-cantilevers were used in the Wheatstone bridge, V was twice of (9) Hence, to obtain a 1-V magnitude on the output of the chip (V in Fig. 3), the total gain of the signal processing circuits of the three MEMS sensors should be 250, 33.3, and 14.3, respectively.…”

“…However, most respiration-related instruments are large and expensive, rendering them only affordable for hospitals. To make respiration monitoring available for homecare patients, one solution is to embed sensors in a bed and sense respiration indirectly by detecting body movements [7]- [9]. However, respiration can only be monitored when patients lie on the bed.…”

Heart rate estimation from FBG sensors using cepstrum analysis and sensor fusion

“…There have been different ways of fusing the multichannel BCG signals. In [3], signals from sensors are summed together before A/D conversion. In [4], spectra from different sensors are averaged, before cepstrum is derived.…”