title: A theory of predicting respiratory tract deposition of inhaled particles in man.
abstract: The respiratory tract deposition of inhaled aerosol particles is due to three principal mechanisms: inertia impaction, Brownian diffusion and gravitational settling. A theory is developed to predict the particle deposition and its distribution in human respiratory tract for any breathing condition. A convection-diffusion equation for the particle concentration with a particle-loss term is used to describe the transport and deposition of particles. In this equation, an apparent diffusion coeffcient due to the velocity nonuniformities in the lung is introduced and is found to be the dominant diffusion mechanism. Expressions for deposition by various mechanisms in dead-space airways and alveolated airways are alo derived. The governing equation is solved numerically with Weibel's lung model A. The airway dimensions, however, are scaled to account for the average lung volume. The total depositions in the lung for particle sizes ranging from 0.2 micron to to 3.0 micron are computed for various steady breathing conditions. The results agree well with recent measurements using bis(2-ethylhexyl) sebacate particles and are less than the previous theoretical predictions. The regional depositions as well as the detailed deposition profiles along the airways are also calculated and discussed.
mesh_terms: D000336:Aerosols; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D010316:Particle Size; D012119:Respiration; D012137:Respiratory System; D013990:Tidal Volume
chemical_list: D000336:Aerosols