Feasibility Study for Unconstrained Respiration Monitoring Based on Multi-Way Approach Using an Acceleration and Force Sensing Module

The purpose of this paper was to validate the feasibility of a proposed sensing module for multiway respiratory monitoring. The proposed monitoring system was implemented using an ultralow-power microcontroller, that included a three-axis accelerometer, an analog/digital input port to connect to an external sensor, and a Bluetooth module for wireless communication. We developed an accelerometer-equipped wireless sensing module and a layered-architecture external strip-type force sensor interface for respiration monitoring. In the feasibility experiment, the accelerometer-equipped module was inserted in a pillow and strip-type force sensors were placed under each of the head, chest, and abdomen to investigate the performance of the respiration measurement in terms of the measurement position. Twelve subjects participated in the experiment, and signals from the accelerometer and the strip-type force sensor were simultaneously recorded during sleep. The results of the experiment showed that the deviation in length of the respiration cycle was estimated with errors under 250 ms in the acceleration signal and the signal from the strip force sensors.