The Effect of Capillary Dimension on Gas Transport in Alveolar Region of the Lungs

Convection in blood capillary gas transport has been considered negligible for many years. For instance, blood flow effect on gas transport in capillaries was neglected in the recent work of Hsia et al. (1995) based on the seminal work by Aroesty and Gross (1970) who studied steady-state gas transfer in a straight muscle capillary including convection effects by assuming an axisymmetric (cylindrical capillary) model with cylindrical RBCs. The goal of the current study is to demonstrate the effects of red blood cell (RBC) shape and channel dimension on convective gas transport in an alveolar capillary. This report presents numerical simulations of carbon monoxide diffusion onto the alveolar region with capillary blood flow. The alveolar region involves three basic constituents namely the tissue (a region including the alveolar and capillary membranes and the interstitial fluid), the blood plasma (a liquid region), and the RBCs as shown in Figure 1. Simulations of a single, straight capillary with one parachute-shaped RBC is considered in this preliminary study.