Oxygen transport studies of normal and sickle red cell suspensions in artificial capillaries

Oxygen transport from normal and sickle red cells was studied under known and carefully controlled conditions simulating the microcirculation. Oxygenated red cell suspensions became deoxygenated as they traversed silicone rubber artificial capillaries of 27 microns diameter. Oxygen saturation values of the flowing red cell suspensions were measured at several axial positions along the artificial capillary by use of a microspectrophotometric technique. Oxygen saturation decreased with increasing distance from the entrance of the artificial capillary and was influenced strongly by the flow rate. Under the same hematocrit and flow conditions, the rate of oxygen saturation decrease was significantly higher for the sickle red cells than that for the normal red cells. Similar results were obtained by use of a mathematical simulation of oxygen transport in the microcirculation for both normal and sickle red cells. Sickle red cells would be expected to have a higher diffusional resistance to oxygen transport than would normal red cells. However, the higher diffusional resistance is more than offset by the lower oxygen affinity of the sickle cells. The difference in oxygen affinity appears to account for the difference in oxygen transport rates between normal and sickle red cells.