Contributions of oxygen dissociation and convection to the behavior of a compartmental oxygen transport model.

We previously derived a compartmental model for oxygen transport in vascular blood in which lumped terms, representing convective and oxygen dissociative effects, were obtained from a distributed model by space averaging. In this paper, we compare the results of this model and those of another compartmental model from the literature in which these terms were selected arbitrarily. The use of space-averaged parameters resulted in a more distinct difference in calculated partial pressures of oxygen between capillary and venule compartments, more accurate distribution patterns for partial pressures of oxygen through the venule compartments, and a capability to simulate conditions under which mean oxygen partial pressure in tissue is higher than in the venules. These results are supported by available experimental findings. Results also showed that the employment of space-averaged convective terms had a greater effect on the distribution of compartmental partial pressures than did the use of the cross-sectional averaged oxygen-hemoglobin binding function. The latter produced significant changes only for certain compartments, and only under extreme physiologic conditions. The results demonstrate our model's ability to reflect relationships among capillary, venule, and tissue compartmental partial pressures under varying conditions.