[The convection and diffusion of oxygen and carbon dioxide in the human airway]

The convective-diffusive problems of oxygen and carbon dioxide in human airway at normal respiratory status were studied theoretically in the present paper. The human airway was idealized as a bifurcated(two-branch) trachea tree, based on the understanding of the physiological structure of the human airway, and on Horsfield-Wanner optimization analysis about the trachea system status. It was assumed that the gases in the airway were incompressible, viscous fluid, due mainly to the characteristics of the low pressure drop and low rate of the gases within the human airway. One dimensional, non-steady convective-diffusive equations of oxygen and carbon dioxide were solved using Lax-Wendroff finite difference method, i.e., the so called three-legged finite difference method. The boundary conditions were set up according to the two different situations, respectively. The computational results showed the reasonable distributions of the concentration of oxygen and carbon dioxide in the human airway, respectively.