The effect of separate red blood cells on capillary tissue oxygenation calculated with a numerical model.

In simplified models that describe large quantities of capillaries the capillary content is considered to be homogeneous for oxygen transport; but, in reality, the capillaries contain discrete red blood cells (RBCs), and this discreteness will affect oxygen transport from the capillary to the tissue. This was previously investigated with an analytical model, where RBCs were modelled as point-like sources. A numerical approach is used in this investigation, and the results are compared with the analytical model. In both models the effect of the particulate nature of blood depends on the haematocrit and on the RBC velocity. There is only a minor difference between the two models. For rat hearts, the correction factor used in this study, the extraction pressure, can be up to 3 kPa (23 mmHg).