Effects of red cell spacing and red cell movement upon oxygen release under conditions of maximally working skeletal muscle.

RBC spacing in capillaries plays an important role in that it determines the total number of RBCs contained in a capillary and, therefore, the total O2 flux out of the capillary. The detrimental effects of increased RBC spacing upon capillary O2 release are in part compensated for by enhanced O2 release out of single RBCs due to improved diffusion geometry and RBC movement. Non-uniformity of O2 flux brought about by the particulate nature of blood is considerably smaller than calculations which do not consider RBC movement indicate. It creates oscillations in the O2 supply to the tissue, the periodicity of which is fast, however, compared to the time constant of the PO2 decay in a temporarily unsupplied tissue. We conclude that non-uniformity of O2 flux out of capillaries due to large inter-erythrocytic plasma gaps does not play an important role for tissue O2 supply as long as average RBC spacing is sufficiently small to guarantee an appropriate overall capillary O2 flux.