Numerical modelling of airflow and aerosol particle delivery in cats with bronchial and non-bronchial disease.

Feline lower airway disease comprises a spectrum of inflammatory conditions, including asthma, which is commonly treated with inhaled glucocorticoids. This study employs computed tomography (CT)-based computational fluid dynamics (CFD) models to characterize airflow dynamics in feline lower airways with and without bronchial disease (BD and NBD), evaluating velocity, pressure, wall shear stress, and airway resistance under different flow conditions. In addition, deposition patterns of two aerosol particle sizes (1 µm and 10 µm) were assessed within the trachea and bronchi. Geometrical reconstructions of the trachea and lobar bronchi were generated from CT scans of 24 cats, classified into BD and NBD groups. Simulations were performed using two airflow conditions and two particle diameters. Airflow parameters and aerosol particle deposition were calculated for each model. A trend toward higher values of most airflow parameters was observed in the NBD group, except for expiratory resistance and velocity. However, no statistically significant differences in airflow parameters were identified between groups. Particle deposition analysis showed a higher deposition fraction for larger particles, with 10 µm particles depositing more frequently on bronchial walls than 1 µm particles in both groups. Overall, CT-based CFD analysis revealed no significant group differences in resistance, pressure, wall shear stress, or velocity. Nevertheless, particle size influenced deposition patterns, with larger particles showing increased bronchial trapping. Although the initial hypothesis was not confirmed, this feasibility and characterization study establishes a methodological framework for future in silico investigations of feline lower airway disease providing preliminary physiologically and clinically relevant insights.