Deposition of fibrous aerosol in model bifurcating tubes

Abstract

A model of the third lung bifurcation with dimensions based on the symmetric model A of Weibel was designed to study lung deposition of fibrous aerosols. The fibrous aerosols were drawn at a steady inspiratory flow. Glass fibers deposited on the daughter tubes and penetrating the tubes were observed by means of scanning electron microscopy (SEM) and were classified into three parts according to their length, i.e. 10–20 μm, 20–40 μm, and 40–80 μm. Then the deposition velocities and fraction of deposited fibers were calculated for these bifurcating tubes. The results indicated that the deposition ‘hot spot’ of the fibers was located at the carinal ridge. The fibers on the tube surface were clearly oriented parallel to the direction of the flow. The secondary flow in daughter tubes was also observed. In agreement with the theoretical values predicted by Harris and Fraser [(1976) Am. ind. Hyg. Ass. J. 37, 73], the deposited fraction presented in this study increased with an increase in fiber length, but the deposited fractions had much smaller values than their calculated results for each fiber length.