Particle deposition in the human tracheobronchial airways due to transient inspiratory flow patterns

Considering realistic tracheobronchial airways, transient airflow structures and micro-particle deposition patterns were simulated with an in-house finite-volume code for typical inhalation waveforms and Stokes numbers, i.e., the average flow rates at the trachea inlet, Qin,av, are 15 and and the mean Stokes number at the trachea inlet, Stmean,trachea, is in the range of 0.0229 Stmean,trachea 0.0915, respectively. While the overall airflow fields exhibit similar characteristics, the local flow patterns which influence particle deposition are largely affected by secondary flows (for both Qin,av=15 and ) as well as airflow turbulence (when ). The particle deposition fraction is a strongly transient function according to a given inhalation waveform. In light of the importance of targeted drug-aerosol delivery, it is shown that the relation between particle-release positions at the trachea inlet and particle depositions at specific lung sites are greatly influenced by the complex airway geometry and the flow-rate magnitude. For laminar flow, the particle-release points are deterministic and unique, as required for optimal drug-aerosol targeting.