Numerical study on the deposition distribution and mechanism of inhaled drug particles in various regions of the realistic inhaler-airway model

Inhaled drug delivery is widely used in the treatment of respiratory diseases. Understanding the deposition mechanisms of dry powder inhalers (DPIs) in different regions of the airway is crucial for inhaler development and prediction of the deposition distribution of drug particles. And the insertion of the inhaler will significantly alter the pattern of airflow in the airway. The main objective of this study is to systematically investigate the distribution and mechanism of aerosol particle deposition in various regions of the inhaler-airway model. Computational fluid dynamics (CFD) was used to simulate the effect of inhalation flow rate on the deposition of drug particles in various regions of the airway. The discrete phase model (DPM) was adopted to track the deposition trajectories of drug particles. Three different inhalation flow rates together with six particle sizes and five particle densities were analyzed. The results indicated that the overall deposition fraction of drug particles gradually increased with particle size and density. The pattern of depositional distribution in other local areas is quite different from the overall pattern except in the oral. The deposition fraction in the pharynx was much larger than in the other local regions, the deposition fractions in the larynx, trachea, carina and bronchi were less than 5 %. The increase in density increases the deposition fraction of particles in various regions throughout the respiratory tract when the inhalation flow rate is 30 L/min. Most of the particles in the oral are deposited on the tongue, and the particles in the bronchus are more distributed in the main trunk, while deeper in the bronchus, particles are also deposited in the bifurcation region. The subject's inhalation posture also affects the local distribution of the airflow. The findings of present study can help to guide the optimization and in vitro-in vivo correlation of DPIs.