Effect of the laryngeal jet on particle deposition in the human trachea and upper bronchial airways

Preferential sites of particle deposition within the human respiratory system are known to correlate with primary cancer sites, and are therefore important in the etiology of neoplastic respiratory diseases. In this study, we characterized the intrabronchial and intratracheal patterns of deposition in a hollow cast of a human larynx-tracheobronchial tree, and examined the effects of airflow and turbulence on particle deposition by performing airflow measurements in the hollow cast and an “ideal” airway bifurcation model.

Experimental results revealed a deposition “hot spot” for particles greater than 2 μm in mass median aerodynamic diameter in the trachea at 2 cm below the larynx. The enhancement of deposition in the trachea was studied by making comparative airflow and detailed morphometry measurements in a hollow lung cast and in an “ideal” model. The larynx had a significant effect on the local flow field in the trachea of the hollow cast and this effect extended to and beyond the tracheal bifurcation. This accounted for some of the difference in flow field at the bifurcation between the cast and an “ideal” model. Additional differences were related to the different shapes of the transitional regions near the bifurcation.