Aerodynamic Simulation of Small Airway Resistance: A New Imaging Biomarker for Chronic Obstructive Pulmonary Disease

Di Zhang,1,&ast; Yu Guan,1,&ast; Xiuxiu Zhou,1 Mingzi Zhang,2 Yu Pu,1 Pengchen Gu,2 Yi Xia,1 Yang Lu,2 Jia Chen,2 Wenting Tu,1 Kunyao Huang,2 Jixin Hou,2 Hua Yang,2 Chicheng Fu,2 Qu Fang,2 Chuan He,2 Shiyuan Liu,1 Li Fan1 1Department of Radiology, Second Affiliated Hospital, Naval Medical University, Shanghai, People’s Republic of China; 2Scientific Research Department, Shanghai Aitrox Technology Corporation Limited, Shanghai, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Li Fan; Shiyuan Liu, Department of Radiology, Second Affiliated Hospital, Naval Medical University, 415 Fengyang Road, Shanghai, 200003, People’s Republic of China, Tel +13564684699 ; +13761304518, Fax +86 21 63587668, Email czyxfl@smmu.edu.cn; radiology_cz@163.comPurpose: To develop a novel method for calculating small airway resistance using computational fluid dynamics (CFD) based on CT data and evaluate its value to identify COPD.Patients and Methods: 24 subjects who underwent chest CT scans and pulmonary function tests between August 2020 and December 2020 were enrolled retrospectively. Subjects were divided into three groups: normal (10), high-risk (6), and COPD (8). The airway from the trachea down to the sixth generation of bronchioles was reconstructed by a 3D slicer. The small airway resistance (RSA) and RSA as a percentage of total airway resistance (RSA%) were calculated by CFD combined with airway resistance and FEV1 measured by pulmonary function test. A correlation analysis was conducted between RSA and pulmonary function parameters, including FEV1/FVC, FEV1% predicted, MEF50% predicted, MEF75% predicted and MMEF75/25% predicted.Results: The RSA and RSA% were significantly different among the three groups (p< 0.05) and related to FEV1/FVC (r = − 0.70, p < 0.001; r = − 0.67, p < 0.001), FEV1% predicted (r = − 0.60, p = 0.002; r = − 0.57, p = 0.004), MEF50% predicted (r = − 0.64, p = 0.001; r = − 0.64, p = 0.001), MEF75% predicted (r = − 0.71, p < 0.001; r = − 0.60, p = 0.002) and MMEF 75/25% predicted (r = − 0.64, p = 0.001; r = − 0.64, p = 0.001).Conclusion: Airway CFD is a valuable method for estimating the small airway resistance, where the derived RSA will aid in the early diagnosis of COPD.Keywords: COPD, small airway disease, CT, fluid dynamics