title: Convective gas transport in the pulmonary acinus: comparing roles of convective and diffusive lengths.
abstract: To investigate the relative importance of convection and diffusion in the transport of oxygen in the pulmonary acinus, it is often useful to locate the transition from convection-dominated to diffusion-dominated transport. Traditionally, this is done by estimating the values of a Peclet number. This dimensionless number compares the bulk ductal flow velocity at an acinar generation with a diffusion velocity over a characteristic length scale. Here, we revisit the convection-diffusion transition by comparing the relative importance of convective and diffusive lengths. We introduce the ratio of such lengths (L(conv)/L(diff)) to quantify the extent of convective transport in the acinus over an inhalation phase. We distinguish between convection along the acinar airways and within alveoli, respectively. Results for L(conv)/L(diff) suggest that convection in acinar ducts may play a potential role in more peripheral airways compared with values obtained for a Peclet number. Within alveoli, however, independent of acinar depth, oxygen transport is governed by diffusion as soon as molecules enter within alveolar cavities.
authors.affiliation: Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA. sznitman@princeton.edu
authors.forename: Josué
authors.initials: J
authors.lastname: Sznitman
mesh_terms: D001692:Biological Transport; D004058:Diffusion; D005740:Gases / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*
chemical_list: D005740:Gases