A Feasible Computational Fluid Dynamics Study for Relationships of Structural and Functional Alterations with Particle Depositions in Severe Asthmatic Lungs

Tis study aims to investigate the efect of altered structures and functions in severe asthma on particle deposition by using computational fuid dynamics (CFD) models. Airway geometrical models of two healthy subjects and two severe asthmatics were reconstructed from computed tomography (CT) images. Subject-specifc fow boundary conditions were obtained by image registration to account for regional functional alterations of severe asthmatics. A large eddy simulation (LES) model for transitional and turbulent fows was applied to simulate airfows, and particle transport simulations were then performed for 2.5, 5, and 10 Dm particles using CFD-predicted fow felds. Compared to the healthy subjects, the severe asthmatics had a smaller air-volume change in the lower lobes and a larger air-volume change in the upper lobes. Both severe asthmatics had smaller airway circularity (Cr), but one of them had a signifcant reduction of hydraulic diameter (Dh). In severe asthmatics, the larger air-volume change in the upper lobes resulted in more particles in the upper lobes, especially for the small 2.5 Dm particles. Te structural alterations measured by Cr and Dh were associated with a higher particle deposition. Dh was found to be the most important metric which afects the specifc location of particle deposition. Tis study demonstrates the relationship of CT-based structural and functional alterations in severe asthma with fow and particle dynamics.