A 4-Channel Piezo Transducer Based Flexible Hybrid Sensor for Respiratory Monitoring

Abstract

Monitoring of breathing under different physical conditions is important in personal health tracking. Many researchers showed the importance of respiratory rate (RR) monitoring as an early anticipation of a serious problem in hospitals [1] [2] . There are some solutions for respiratory monitoring that are not ideal as a wearable monitoring system due to their sensitivity to body motions [3] [4] . A novel method of ultrasound based respiratory monitoring was reported before [5] [7] . The system monitors the diaphragm motions using ultrasound waves. However, the device error was higher in tests where body was under big motions resulting in sensor displacements due to skin stretch. Arm abduction and adduction had the highest amount of skin artifacts. In this work, we show an advancement in a respiratory monitoring system based on diaphragm wall motion tracking which is less sensitive to motion artifacts. Diaphragm motions are measured by a designed flexible hybrid ultrasound sensory system with four ultrasound PZT5 piezo transducers. Use of flexible hybrid electronics allows integrating both rigid electronics and printed materials on a flexible substrate resulting in thin, lightweight and conformal device. Conformal interface to human skin significantly increases the signal-to-noise ratio for the measurement of our respiratory signal. We evaluate the accuracy and robustness of the sensory system. Measurements are referenced to an SPR-BTA spirometer. All tests are done in non-stationary human body situations to evaluate the sensor in a real life.