Theoretical analysis of effects of blood substitute affinity and cooperativity on organ oxygen transport

Hemoglobin-based O(2) carriers (HBOCs), which are developed as an alternative to blood transfusion, provide O(2) delivery. At present, there is no model to predict the O(2) transport for a red blood cell-HBOC mixture on a whole organ basis. On the basis of the first principles of mass balance, a model of O(2) transport for an organ was derived to calculate venous Po(2) (Pv(O(2))) for a given inlet arterial Po(2) (Pa(O(2))), blood flow, and oxygen consumption. The model was validated by using several in vivo animal studies on HBOC administration for a wide range of HBOC oxygen-binding parameters and predicted Pv(O(2)) for various Pa(O(2)) in the same species. The model was also used to predict the effect of HBOC affinity and cooperativity on Pv(O(2)) for humans. The results indicate that Pv(O(2)) can be increased at a constant blood flow-to-oxygen consumption ratio by reducing the affinity of HBOC for normoxia and mild hypoxia; however, a high-affinity HBOC would be more efficient in maintaining higher Pv(O(2)) for severe hypoxia (Pa(O(2)) < 40 Torr).