Anatomically based three-dimensional model of airways to simulate flow and particle transport using computational fluid dynamics

We have studied gas flow and particle deposition in a realistic three-dimensional (3D) model of the bronchial tree, extending from the trachea to the segmental bronchi (7th airway generation for the most distal ones) using computational fluid dynamics. The model is based on the morphometrical data of Horsfield et al. ( Horsfield K, Dart G, Olson DE, Filley GF, and Cumming G. J Appl Physiol 31: 207 - 217, 1971) and on bronchoscopic and computerized tomography images, which give the spatial 3D orientation of the curved ducts. It incorporates realistic angles of successive branching planes. Steady inspiratory flow varying between 50 and 500 cm(3)/s was simulated, as well as deposition of spherical aerosol particles (1 - 7 mum diameter, 1 g/cm(3) density). Flow simulations indicated nonfully developed flows in the branches due to their relative short lengths. Velocity flow profiles in the segmental bronchi, taken one diameter downstream of the bifurcation, were distorted compared with the flow in a simple curved tube, and wide patterns of secondary flow fields were observed. Both were due to the asymmetrical 3D configuration of the bifurcating network. Viscous pressure drop in the model was compared with results obtained by Pedley et al. ( Pedley TJ, Schroter RC, and Sudlow MF. Respir Physiol 9: 387 - 405, 1970), which are shown to be a good first approximation. Particle deposition increased with particle size and was minimal for similar to 200 cm(3)/s inspiratory flow, but it was highly heterogeneous for branches of the same generation.