Assessment of pulmonary function using an infrared Time-of-Flight depth image sensor in patients with COPD

<bold>Background</bold> Chronic Obstructive Pulmonary Disease (COPD) is characterized by irreversible airflow obstruction and is commonly assessed by pulmonary function tests (PFT). However, PFTs are effort dependent and require forced exhalation by the patient. Performing pulmonary function tests during the coronavirus disease-2019 (COVID-19) pandemic had to be considered carefully due to the potential for aerosol transmission. Therefore, a non-contact test option to assess COPD would be beneficial. <bold>Aims and Objectives</bold> To validate an infrared Time-of-Flight (ToF) depth image sensor of a smartphone to estimate pulmonary function during spirometry in COPD patients. <bold>Methods</bold> All subjects simultaneously performed spirometry maneuvers and thoracic volume movement by analyzing the ToF sensor images. Pulmonary function tests included forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). FEV1/FVC ratio was also calculated. We then compared thoracic volume movement and spirometry measurements including FEV1, FVC, and the FEV1/FVC ratio. <bold>Results</bold> A total of 48 COPD patients were included. The mean age was 77.6 (59-87), and 43 (90%) were male. The thoracic volume movements were significantly correlated with FEV1 (r=0.729, P<0.0001), FVC (r=0.675, P<0.0001), and FEV1/FVC (r=0.772, P<0.0001). <bold>Conclusions</bold> Thoracic volume measurements by ToF sensor images were able to predict the pulmonary function values in patients with COPD. Three-dimensional surface scanning technologies appear promising as an efficient non-contact screening tool for the detection of COPD.