I:E Ratio Estimation Using a Patch-Type Multimodal Sensor for Pulmonary Function Screening of COPD

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the world, and doctors expect the number of patients to increase by 23% in 2050. Patients experience dyspnea during physical exertion due to compromised pulmonary gas exchange capacity. Deterioration of pulmonary function is expected to appear in the Inspiratory to Expiratory ratio (I:E ratio). However, the I:E ratio is often unmonitored even in hospitals. The I:E ratio is not yet a standard index for health monitoring; therefore, it remains untouched by most studies. Therefore, we aim to estimate the I:E ratio from the proposed patch-type multimodal sensor for pulmonary function screening of prediagnosed COPD patients. We conducted experiments with three types of I:E ratios on 14 healthy participants. The first objective was a trend analysis of photoplethysmography (PPG) and three-axis acceleration respiratory signals acquired from the proposed multimodal sensor. From the results, the best results of the four signals differed depending on signal amplitude, baseline wander, inconsistency, and vibration. Hence, by formulating a signal quality evaluation step, we proposed a signal selection method to systematically determine the best of the four signals for I:E ratio estimation.