Oxygen delivery from fluorocarbon emulsions--aspects of convective and diffusive transport.

Perfluorocarbons (PFCs) deliver oxygen due to their physical characteristics and the convective delivery to tissues; this has been amply demonstrated in numerous animal models and in clinical trials. PFC emulsions have also been used for organ perfusion and augmentation of oxygenation to cell cultures. By reason of their small particle size, PFC emulsions penetrate collateral capillaries of an ischemic microcirculation, both supplying oxygenation and possibly restoring flexibility of acidotically stiffened erythrocytes by reinstituting aerobic metabolism. There is also evidence that PFCs can augment tissue oxygenation by increasing oxygen solubility in the plasma phase of blood; this improves diffusion gradients between plasma and tissues even at relatively low doses of PFC. This hypothesis is supported by the ability of PFCs to increase oxygen tensions in tissues such as blood, brain, liver, kidney, pancreas, skeletal muscle, retina etc. PFCs can also on occasions increase critical oxygen extraction coefficients and should therefore be effective in supporting oxidative metabolism in states of extreme cardio-respiratory insufficiency. This theory represents a new concept in oxygen delivery and may define a new class of therapeutic agents that can improve tissue oxygen supply in various pathological states involving low oxygen delivery and ischemia.