COMPUTATION OF LOCAL ENHANCEMENT FACTORS FOR THE QUANTIFICATION OF PARTICLE DEPOSITION PATTERNS IN AIRWAY BIFURCATIONS

Spatial deposition patterns in two different geometric models of bronc hial airway bifurcations were computed by solving numerically the 3D N avier-Stokes equations and simulating particle trajectories under the simultaneous action of impaction, sedimentation, diffusion, and interc eption by Monte Carlo techniques. To quantify the inhomogeneities of t he predicted deposition patterns the whole surface of the bifurcation was scanned with a prespecified surface area element to determine the number of particles deposited per unit surface area. The local deposit ion density in a given surface element, relative to the average deposi tion density, was then defined as the local deposition enhancement fac tor. In the present study, the computation of local deposition enhance ment factors focused on inspiratory particle deposition patterns. Our results revealed that the distributions of local deposition enhancemen t Factors along the surface of a bifurcation exhibit strong inhomogene ities for all particle sizes and bifurcation geometries considered her e. The maximum enhancement factor in a bifurcation was found to be abo ut 100 in the upper bronchial airways for any particle size in the dia meter range from 0.01 to 10 mu m, obtained with a 100 mu m x 100 mu m scanning element. These numerically computed local deposition enhancem ent factors can be directly applied to inhalation health effect protoc ols to consider the effects of highly localized doses. (C) 1998 Elsevi er Science Ltd. All rights reserved.