Towards Wearable-based Lung Sound Intensity Assessment Leveraging Impedance Pneumography

Respiratory diseases are a leading cause of mortality. Lung sound (LS) intensity is an important auscultation component that relates to sound transmission and generation in health and disease. The assessment of LS intensity outside laboratory and clinical settings remains understudied due to its dependency on auscultation location, respiratory phase, and airflow rate. Simultaneous Impedance Pneumography (IP) and multi-channel LS measurement presents a unique opportunity to provide such context. In this study, we evaluated the feasibility of fusing IP and LS to quantify the relationship between airflow and LS amplitude, and the effectiveness of continuous flow-correction. Wearable-based IP and LS at three different locations were measured simultaneously with spirometer airflow signals on 10 healthy volunteers while performing breathing maneuvers. The relationship between calibrated IP peak inspiratory flow (PIF) and inspiratory LS amplitude features, with and without flow-correction, was evaluated with correlation analysis. Our results confirmed the well-established significant relationship between LS amplitude and airflow (R-2 >= 0.93, p < 0.001) and demonstrated the flow-correction effectiveness in the 0.5-2.8 L/s PIF range. As such, this work may pave the way for a wearable-based quantitative LS intensity assessment.