Evaluation Of Pulmonary Ventilation Function Applied On Airway Diseases:A Computational Fluid Dynamics Study

Pulmonary function testing and computed tomography(CT)of the chest are the main tools used to examine functional and imaging changes in patients’ lungs,respectively.However,these tests fail to combine functional testing and imaging diagnostics together.In order to better quantitatively assess the changes in respiratory function and treat respiratory diseases,this paper uses computational fluid dynamics(CFD)techniques to perform numerical simulations of ideal models and patient-specific models to analyze the relationship between morphological and fluid dynamics factors and disease progression.Firstly,to investigate the relationship between morphology and fluid dynamics in patients with airway stenosis,ideal models of airway with different morphological parameters were established to investigate the impact of the geometric variations.The geometric variations included stenosis segment location,stenosis segment length and narrowness.The results showed that when the stenosis is in the central airway and stenosis degree is about 70%,the pressure drop in the stenosis segment and the shear stress at the cross-section at the most stenotic point increase significantly.We also selected clinical data of four cases suffering from central airway stenosis and reconstructed a three-dimensional airway tree model based on CT data and performed CFD numerical simulations.We found that the results were consistent with the findings in the ideal model.Secondly,in order to discuss the relationship between fluid dynamics parameters and disease regression,this paper retrospectively analyzed clinical data from five patients with severe COVID-19 admitted in Huangshi City who met the criteria,among which patients were divided into survival group and death group.A 3D airway tree model from the central airway to the 4th-5th level bifurcation was reconstructed from the patients’ CT data before and after treatment,and the volume changes of the bronchi were calculated.In addition,the changes of airflow resistance in the airway were analyzed by using CFD numerical simulation.A negative correlation was found between the volume change of the airway and the change in flow resistance in patients with severe COVID-19(r =-0.7025,p = 0.002).For total airway volume,the mean decrease in the death group was 11.41 ± 15.71%,while the mean increase in the survival group was 1.86 ± 10.80%(p = 0.0232).For lower lobe flow obstruction,the death group increased by 10.97 ± 77.66%,while the survival group decreased by 45.49 ± 42.04%(p= 0.0246).This shows that CFD can be used as a non-invasive assessment index for the diagnosis of patients with respiratory diseases,and the combination of imaging data and CFD analysis for virtual lung function testing is of great significance in revealing the pathogenesis of respiratory diseases.