2017 Military Supplement: Perfluorocarbons, Oxygen Transport and Microcirculation in Low Flow States Mini-Review: Perfluorocarbons, Oxygen Transport and Microcirculation in Low Flow States
The in vivo study of microvascular oxygen transport requires accurate and challenging measurements of several mass transfer parameters. Although recommended, blood flow and oxygenation are typically not measured in many studies where treatments for ischemia are tested. Therefore, the aim of this communication is to briefly review cardinal aspects of oxygen transport, and the effects of perfluorocarbon treatment on blood flow and oxygenation based mostly on studies performed in our laboratory. Since physiologically relevant events in oxygen transport take place at the microvascular level, we implemented the phosphorescence quenching technique coupled with non-invasive intravital videomicroscopy for quantitative evaluation of these events in vivo. Rodent experimental models and various approaches have been employed to induce ischemia including hemorrhage, micro and macro-embolism, as well as microvessel occlusion. Measurements show decrease in microvascular blood flow as well as intravascular and tissue oxygen partial pressure (PO2) following these procedures. In order to minimize or reverse the effects of ischemia and hypoxia, artificial oxygen carriers such as different perfluorocarbons were tested. Well-defined end-points such as blood flow and tissue PO2 were measured since they have significant effect on tissue survival and outcome. In several cases, enhancement of flow and oxygenation could be demonstrated. Similar results were found in vitro: Perfluorocarbon emulsion mixed with blood (from healthy donors and sickle cell disease patients) enhanced oxygen transport. In summary, perfluorocarbons may provide beneficial effects in these models by mechanisms at the microvascular level including facilitated diffusion and bubble reabsorption leading to improved blood flow and oxygenation.