STABLE BLOOD LUBRICATED HYDRODYNAMIC JOURNAL BEARING WITH MAGNETIC LOADING

The Cleveland Clinic Foundation's Innovative Ventricular Assist System (IVAS) is distinguished by the use of a special hydrodynamic journal bearing to support the rotating assembly of the blood pump. In a perma nently implanted blood pump, this bearing's characteristics of long li fe and high reliability are of paramount importance. In addition, this bearing's inherent self-pumping flow and the axial through flow cause d by an imposed end-to-end pressure difference provides good washing, thus guarding against deposition. The basic computer analysis and prel iminary testing results of this bearing were previously presented. Thi s article reports the ongoing studies (both analytic and in vitro test s) on this innovative bearing as a component of the IVAS in general, w ith particular emphasis on its stable operating characteristics and re liability. The absence of vibration attributable to hydrodynamic insta bilities related to the thick fluid film are both calculated and demon strated during testing. A stable operating center of the rotor is show n to be inherent under magnetic side loads and resulting hydrodynamic bearing forces. A low shear as a result of large fluid-film thicknesse s has been calculated, and low hemolysis has been shown by in vitro te sting. Several unique design features of the bearing are believed to b e responsible for this high level of performance.