The influence of fibre shape in lung deposition-mathematical estimates.

Inhaled fibres deposit by sedimentation, diffusion, impaction, and interception in airways of the respiratory system. Long straight fibres may exhibit periodic motiion with ordered orientation in those airways having laminar flow. We assume that irregular fibres are randomly oriented in airways. Mathematical models based on respiratory system architecture, respiratory airflow, and mathematical expressions for deposition mechanisms have been developed to predict deposition in respiratory compartments of fibres in ordered orientation and of various fibre confirgurations in random orientations. The size and shape characteristics of chamber aerosols generated with U.I.C.C. asbestos specimens have been determined. Combinations of the chamber aerosol data with mathematical estimates of deposition suggest that fibre shape as well as size influences the magnitude of deposition in pulmonary spaces. For size distributions such as those of the U.I.C.C. asbestos chamber aerosols, the mathematical models predict pulmonary spaces deposition for straight fibres in ordered orientation about twice as great as for irregular fibres in random orientation.