Effects of airway deformation and alveolar pores on particle deposition in the lungs

The distal lung (G14-G23), which are composed of alveoli and bronchi, are responsible for almost all gas exchange and micro-and nanoparticle deposition in the lungs. In the existing research using computational fluid dynamics, the geo-metric modeling accuracy of the bronchial bifurcation structure is given priority, and then the alveoli are attached to bronchi as discrete spherical crowns. This method ignores the correlation between alveoli. In fact, the alveoli have a tessellated distribution, and adjacent alveoli are connected by several alveolar pores. Due to the huge number of alve-oli, this seemingly small difference will be greatly amplified, which may lead to a large deviation in the prediction of the overall flow. Accordingly, the objective of this study is to construct a two-dimensional distal lung model including the bronchi, acini, and alveolar pores by using the methods of regular hexagonal tessellational subdivision, fusion, and coordinate transformation. A moving boundary is introduced to simulate the process of airflow and particle deposition in the distal lung, and the effects of bronchial deformation, respiratory frequency, and alveolar pores are obtained. The results show that there are significant differences in intrapulmonary flow patterns with and without alveolar pores. Al-veolar pores can establish bypass ventilation downstream of a blockage, thus providing a pathway for particles to enter the airways downstream of the blockage. Changing the respiratory frequency and the amplitude of bronchial deforma-tion will change the relative velocity between particles and moving wall, which, in turn, will change the particle depo-sition efficiency in the distal lung. To summarize this study, a geometric modeling method for the distal lung with alveolar pores is established, and the important roles of detailed characteristics of the distal lung are revealed. The find-ings of this study provide a reasonable hydrodynamic mechanism for the prevention of related respiratory diseases.

Automated summary

This study aims to construct a two-dimensional model of the distal lung including bronchi, acini, and alveolar pores, and reveals the important roles of alveolar pores in intra-pulmonary flow patterns and particle deposition.