Lung Morphometry and Particle Transport and Deposition: Overview of Existing Models

Abstract

Health effects of inhaled particulate matter in the human respiratory tract depend on the total number (or total mass) of particles deposited on human airway surfaces in a single breath or in a given period of time (“total deposition”). A characteristic feature of these effects, however, is their apparent site selectivity. For example, lung cancers in smokers have been detected primarily in bronchial airways. Consequently, the lung cancer incidence in smokers is more aptly related to bronchial deposition (“regional deposition”) rather than to total deposition. Furthermore, the majority of bronchial carcinomas has been found in the segmental and subsegmental bronchi (“differential deposition”), possibly originating at bronchial airway bifurcations (“localized deposition”). While total and regional deposition in human test subjects can be studied by various experimental methods, it is presently not possible to determine experimentally particle deposition in individual airways and within airway bifurcations in situ. Such information can only be provided by mathematical modeling.