Deposition of Fibrous Aerosol in a Model of a Human Lung Bifurcation Under Cyclic Flow Conditions

Abstract

Various lung diseases associated with exposure to fibrous materials have been pointed out by many authors. Pott (1978) proposed the well-known hypothesis that carcinogenic potency depends upon the length, diameter and aspect ratio of inhaled fibres. However, only a small number of experiments have been conducted on the deposition process of fibrous aerosols in airways (Timbrell, 1972; Petra, 1979, Kahn, 1982; Sussman et al., 1991) because of difficulties in the generation and measurement of fibrous aerosols compared to compact aerosols. Myojo (1987, 1990) observed deposited fractions of fibrous aerosols and presented profiles of deposition velocity on a simplified model of bifurcating tubes. The dimensions of the model bifurcation were based on the third and fourth generation of Weibel's lung model A (Weibel, 1963) and a steady inspiratory flow of glass fibre aerosol was employed. Deposited fraction and deposition velocity for a fibre length range were obtained by the direct observation of fibres deposited on the model bifurcation. The current paper presents additional data obtained using a unique breathing simulator (Myojo, 1989) to generate cyclic flow in the model bifurcating tubes. The relationships between fibre diameter, fibre length and deposited fractions were determined for cyclic and steady flow conditions.