Tracheobronchial Airway Deposition of Ultrafine Particles

Abstract
Experimental deposition data have recently been reported for monodisperse aerosols of 0.04, 0.15 and 0.2 μm diameter in the airways of replicate hollow casts of the upper human airways. Because deposition in this particle size range is controlled by diffusion, empirical formulas are derived from the data for deposition efficiency in the trachea and bronchial airways based upon a similarity analysis of the convective diffusion equation. It is found that deposition efficiency is a function of Reynolds number, Schmidt number, the aspect ratio of the airway and the branch angle. The experimental data as well as the new formulas show that deposition is significantly greater than that predicted by the formula using a parabolic velocity profile. This is a result of enhanced convective diffusion due to the presence of turbulence, secondary flow and developing flow in the airways.

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