Model analysis of local oxygen delivery with liposome-encapsulated hemoglobin

Liposome-encapsulated hemoglobins (LHs) are comparable to red blood cells (RBCs) in terms of oxygen (O2)-carrying capacity. The smaller particle size of LHs than of platelets allows their homogeneous dispersion in circulating plasma. In this study, we evaluated the effect of LH transfusion on arterial O2 delivery through vascular trees by simulation. A mathematical model was established on the basis of the coronary arterial anatomy, the conservation of flow and RBC flux, and Poiseuille’s law. The Fåhraeus-Lindqvist, Fåhraeus, and phase separation effects were considered in the model. By assuming steady perfusion, the arterial flow and O2 delivery were calculated for five model trees undergoing the isovolumic replacement of RBCs (0.3 mg hemoglobin (Hb)/mL) with LHs (0.2 mg Hb/mL) or a plasma volume expander (PVE). The RBC–LH exchange increased both the total flow and the total O2 flux but had almost no effect on the relative distribution of O2 flux. In contrast, the RBC–PVE exchange decreased the total O2 flux and increased the proportion of regions receiving a relatively low O2 supply. Thus, LH transfusion may compensate for an enhanced bias in RBC-associated O2 flux under hemodilution and is expected to be beneficial for both total and local O2 delivery.