Numerical investigation of the effects of respiratory modes and ablation lesions on airflow and particle deposition in a pulmonary acinar model

Understanding particle deposition patterns in the pulmonary acinus is essential for early intervention and treatment in acinar diseases. This study numerically investigated the effects of respiratory modes and emphysematous alveolar wall ablation on airflow and particle deposition in a physiologically representative pulmonary acinar model. A heterogeneous acinar model was developed, incorporating alveolar expansion and contraction via the dynamic meshing method, and its validity was confirmed by comparison with published particle deposition data. Airflow and particle transport patterns were then analyzed under varying respiratory modes and degrees of alveolar wall ablation. For particles smaller than 1 μm, deposition decreased with higher breathing frequency and increased with larger tidal volume. Smaller particles penetrated deeper and deposited more uniformly due to strong airflow coupling. Compared with the normal acinus, the lesioned acinus exhibited reduced airflow variability, lower expansion capacity, and a decreased deposition fraction. Alveolar wall ablation impaired lung expansion and restricted distal airflow penetration, leading to localized particle deposition near the acinar entrance. As lesion severity increased, the deposition progressively declined due to altered flow patterns and a reduced surface-to-volume ratio. The particle deposition declined nonlinearly with lesion severity. A 30% wall ablation reduced total deposition by over 40%, whereas further increases to 60% and 90% caused only minor additional decreases, indicating a nonlinear response in which early structural damage disproportionately affects acinar particle deposition. These findings underscore the importance of early intervention to preserve alveolar drug deposition efficiency and improve therapeutic outcomes in patients with progressive pulmonary diseases such as emphysema.