In silico modeling of asymmetric airways: in health and in disease

How do we get infected by diseases like COVID-19? How do atmospheric pollutants impact our health? How to optimize/customize inhalation therapy for specific patients? In order to answer these questions, understanding the physical mechanisms of fluid flow and aerosol transport in the lung becomes crucial. In spite of huge technological improvements in recent years, fully capturing the workings of the lung remains out of reach. Primary reasons behind this challenge are the huge variations in length scales (L ∼ 1 cm - 100 μm) and flow regimes (Re ∼ 1000 - 0.1), as well as the complicated geometry of the airways.

Our research explores the structure-function relationships in the airways through in-silico methods of varying complexities. We show that natural asymmetry of the human lung enhances particle filtration through tracheobronchial deposition by around 5%, while other parameters like gas exchange surface area, volume occupied by the airways and resistance to airflow deviate by more than 10% of their optimal value. Through our investigations of regional deposition in the lung, we show how asymmetry, particle size, breathing rate and bronchoconstriction (a common marker of several lung diseases) influence the distribution of deposition in the lung. On one hand, these insights shed light on airborne infection mechanisms. On the other hand, they guide precise dosage determination of medications as well as the choice and design of delivery devices.