Analysis, Design, and Experiment of FVC Detection Device Using the Cross Four-Electrode Method

The early screening and prevention of chronic respiratory diseases are very important. To achieve the monitoring and management of chronic obstructive pulmonary disease (COPD), this article proposes a new lung impedance measurement method, which uses a cross four-electrode structure. It effectively solves the problems of noncompliance of traditional instruments, risk of cross-infection, and nononline monitoring. Compared with the traditional impedance measurement method, the measurement accuracy of lung function parameters is improved. Using the detection device, the equivalent impedance of the chest was rapidly measured from two orthogonal directions when the people were in the same breath state. The maximum expiratory and inspiratory thoracic impedance was obtained by analyzing 30 samples. The measurement of lung function parameters is realized by solving the change value of impedance and its relationship with the chest circumference. Experiments proved that the cross four-electrode method could consider the two directions of equivalent thoracic impedance, enrich the measurement parameters of thoracic impedance, and make the test results of pulmonary function parameters have good consistency with the results of standard methods. Correlation coefficients of test indexes forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were 0.967 and 0.955 respectively. The consistency boundary diagram showed that more than 95% of monitoring data of the subjects fell within the scope of the consistency boundary, and the maximum relative error of measurement was only 4.65%.