Simulation of fiber deposition in bronchial airways.

Penetration probabilities of inhaled man-made mineral fibers to reach central human airways were computed by a stochastic lung deposition model for different flow rates and equivalent diameters. Results indicate that even thick and long fibers can penetrate into the central airways at low flow rates. Deposition efficiencies and localized deposition patterns were then computed for man-made fibers with variable lengths in a three-dimensional physiologically realistic bifurcation model of the central human airways by computational fluid dynamics (CFD) techniques for characteristic breathing patterns. The results obtained for inspiratory flow conditions indicate that deposition efficiencies were highest for parallel orientation of the fibers, increasing with rising flow rate, branching angle, and fiber length at all orientations. Furthermore, deposition patterns were highly inhomogeneous and their localized distributions showed hot spots in the vicinity of the carinal ridge and at the inner sides of the daughter airways. Comparisons with other theoretical results demonstrate that the equivalent diameter concept, if including interception, presents a reasonable approximation for the parameter ranges employed in the present study.