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.
Bronchi ; physiology ; Carbon Dioxide ; metabolism ; Convection ; Diffusion ; Humans ; Models, Biological ; Oxygen ; metabolism ; Trachea ; physiology

Based on the principles of the sheet-flow model, oxygen transport in pulmonary capillaries was considered as a process in which oxygen first enters plasma through the respiratory membranes, and then combines with the Hbc. A novel mathematical model about oxygen transport in pulmonary capillaries was established according to the relationship of the oxygen concentration inside the red blood cells with the concentration of haemoglobin and the blood saturation, and according to the basic formula for the correlation between blood saturation and oxygen partial pressure. Furthermore, we adopted the Lax-Wendroff Finite Difference Method and obtained certain valuable results under different physiological states. It was well concluded that the established model could be used to provide useful data for medical researchers as well as doctors.
Biological Transport ; physiology ; Capillaries ; physiology ; Humans ; Models, Biological ; Oxygen ; blood ; Partial Pressure ; Pulmonary Alveoli ; blood supply ; Pulmonary Circulation ; physiology ; Pulmonary Gas Exchange