The impact of asymmetric branching on particle deposition in conducting airways

Abstract

Inhalation exposes individuals to a diverse range of airborne particles carrying potential health risks. Airflow and particle transport behavior is highly sensitive to airway geometry. Therefore, it is a huge source of inter-subject variability — in both disease development as well as inhalation therapy outcomes. Numerical simulations of multi-phase flow of particle-laden air within the respiratory system has emerged as a key tool in assessing these complex physical phenomena. This study investigates the implications of bifurcation asymmetry in airway geometry on the fate of inhaled particles by employing Computational Fluid Dynamics (CFD) calculations. To that end, we use single generation ‘Y-units’. Then we extend the study to multi-generation (G5−G11) bronchial tree networks, both symmetric and asymmetric. An Eulerian–Eulerian approach was employed to solve for the coupled air-flow and particle transport equations, utilizing the OpenFOAM® CFD package. The relationship between lung structure and particle dynamics is revealed by analyzing the effects of asymmetry on particle transport and deposition. Our results show that although geometric asymmetry may not have a significant impact on the deposition fractions of single Y-units, its effects keep accumulating over multiple generations. This study also sheds light on local deposition patterns, identifying the specific deposition hot spots, leading to a comprehensive understanding of inhaled particle behavior in distinct lung geometries.