Mixing and deposition of Brownian particles in model alveolus.

Abstract

Inhaled submicron particles readily penetrate into alveolar regions of the human lung, where the behavior of these particles is largely influenced by mixing between inhaled air and residual air. In the present work, an experimental technique to study mixing and deposition of Brownian particles in an expanding/contracting balloon as a model alveolus was developed by employing a “wash-out” experimental technique. Further, applying a simple number balance equation of particles, the mixing volume and deposition coefficient during a breath were obtained. It was found that (i) there exists a critical value in the duration of balloon expansion/contraction over which Brownian diffusion of aerosol enhances mixing between aerosol and clean air, and the critical duration of balloon expansion/contraction is longer for a larger expansion/contraction volume of the balloon; and (ii) at the same expansion/contraction volume of the balloon, the deposition coefficient per breath is larger for a larger expansion/contraction volume.