의복착용형 무선 호흡모니터 시스템

Abstract

Respiration is induced by muscular contraction of the chest and abdomen, resulting in the abdominal volume change. Thus, continuous measurement of the abdominal dimension enables to monitor breathing activity. Conductive rubber cord has been previously introduced and tested to develop wearable application for respiratory measurements. The present study implemented wireless wearable respiratory monitoring system with the conductive rubber cord in the patient's pants. Signal extraction circuitry was developed to obtain the abdominal circumference changes reflecting the lung volume variation caused by respiratory activity. Wireless transmission was followed based on the zigbee communication protocol in a size of 65 mm×105 mm easily put in pocket. Successful wireless monitoring of respiration was performed in that breathing frequency was accurately estimated as well as different breathing patterns were easily recognized from the abdominal signal. CO2 inhalation experiment was additionally performed in purpose of quantitative estimation of tidal volume. Air mixed with 0 ~5% CO2 was inhaled by 4 normal males and the respiratory air flow rate, abdominal dimension change, and end tidal CO2 concentration were simultaneously measured in steady state. CO2 inhalation increased the tidal volume in normal physiological state with a correlation coefficient of 0.90 between the tidal volume and the end tidal CO2 concentration. The tidal volume estimated from the abdominal signal linearly correlated with the accurate tidal volume measured by pneumotachometer with a correlation coefficient of 0.88 with mean relative error of approximately 8%. Therefore, the tidal volume was accurately estimated by measuring the abdominal dimension change.