A new mock circulatory loop was developed for
hemolysis studies associated with the Penn State electric
ventricular assist device (EVAD). This flow loop has several advantages over previously designed loops. It is small enough to accommodate experiments in which only single units of blood are available, it is made out of
biocompatible materials, it incorporates good geometry, and it provides normal physiological pressures and flows to both the aortic outlet and the venous inlet of the pumping device. Experiments with reduced aortic pressure but normal cardiac output showed that
hemolysis in a loop with normal aortic blood pressure was significantly higher than that in a loop with lowered aortic pressure, thereby illustrating the importance of maintaining loop pressures as close as possible to those found in vivo. This data also imply that blood traveling through the left ventricle in an
artificial heart may be subject to higher
hemolysis rates than that traversing the right ventricle. Another set of experiments to determine the effects of 4
hemolysis or drag-
reducing agents (
Pluronic F-68,
Dextran-40,
Polyox WSR-301, and Praestol 2273TR) on blood
trauma due to the EVAD and associated valves was performed. Results indicated that none of the additives significantly reduced
hemolysis under the conditions found in the mock loop. Finally, a compilation of data gathered in these experiments showed that the index of
hemolysis (IH) is dependent on hematocrit (HCT), which suggests that another parameter, IH/HCT, may be more suited to the quantification of
hemolysis.