Particle Deposition in Volumetric Regions of the Human Respiratory Tract

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Abstract
An aerosol bolus technique was used to estimate where inspired particles deposit in the human respiratory tract. Aerosol boli were introduced at preselected points during an inspiration of 1 litre of air and thus penetrated to different depths in the lungs. Di-2-ethylhexyl sebacate droplets of 1 μm diameter served as aerosol particles. Particle losses in the respiratory tract were calculated from recorded instantaneous particle number concentration and respired volume. The deeper a bolus penetrated into the lungs the larger was dispersion and the larger was the fraction of inspired particles which deposited. Dispersion and deposition could be described by a matrix formalism which revealed that dispersion can be neglected for the estimation of deposition when the entire tidal air contains particles. That portion of the respiratory tract ventilated by a tidal volume of 1 litre was then considered as a series of 10 particle collecting regions. The collection efficiency of a region was found to be larger the deeper the region was located in the lungs. However, particle deposition from a single tidal inspiration of an aerosol increased in the first 4 regions and decreased in the last 4 regions. These data are comparable to data that were computed from mathematical deposition models and may be used to evaluate their accuracy.

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