Characterization of Regional and Local Deposition of Inhaled Aerosol Drugs in the Respiratory System by Computational Fluid and Particle Dynamics Methods

The present work describes the local deposition patterns of therapeutic aerosols in the oropharyngeal airways, healthy and diseased bronchi and alveoli using computational fluid and particle dynamics techniques. A user-enhanced computational fluid dynamics commercial finite- volume software package was used to compute airflow fields, deposition efficiencies, and deposition patterns of therapeutic aerosols along the airways. Adequate numerical meshes, generated in different airway sections, enabled us to more precisely define trajectories and local deposition patterns of inhaled particles than before. Deposition patterns show a high degree of heterogeneity of deposition along the airways, being more uniform for nanoparticles compared to micro-particles in the whole respiratory system at all inspiratory flow rates. Extrathoracic and tracheobronchial deposition fractions of nanoparticles decrease with increasing flow rates. However, vice versa happens to the micron-size particles, that is, the deposition fraction is higher at high flow rates. Both airway constrictions and the presence of tumors significantly increased the deposition efficiencies compared to the deposition efficiencies in healthy airways by a factor ranging from 1.2 to 4.4. In alveoli, the deposition patterns are strongly influenced by particle size and direction of gravity. This study demonstrated that numerical modeling can be a powerful tool in the aerosol drug delivery optimization. Present results may be integrated in future aerosol drug therapy protocols.