Affiliations: Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan | Department of Medical Engineering and Cardiology, Institute of Development, Aging and Cancer, Tohoku University, Miyagi, Japan | Department of Biomedical Engineering, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan | Department of Mechanical Engineering, Kobe University, Hyogo, Japan
Note: [] Address for correspondence: Ryo Kosaka, PhD, Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan. Tel.: +81 298 61 7016; Fax: +81 298 61 7848; E-mail: ryo.kosaka@aist.go.jp
Abstract: We have developed a hydrodynamically levitated centrifugal blood pump with a semi-open impeller for long-term circulatory assist. The pump uses hydrodynamic bearings to enhance durability and reliability without additional displacement-sensors or control circuits. However, a narrow bearing gap of the pump has a potential for hemolysis. The purpose of this study is to develop the hydrodynamically levitated centrifugal blood pump with a semi-open impeller, and to evaluate the effect of a bearing gap on hemolytic property. The impeller levitates using a spiral-groove type thrust bearing, and a herringbone-groove type radial bearing. The pump design was improved by adopting a step type thrust bearing and optimizing the pull-up magnetic force. The pump performance was evaluated by a levitation performance test, a hemolysis test and an animal experiment. In these tests, the bearing gap increased from 1 to 63 μm. In addition, the normalized index of hemolysis (NIH) improved from 0.415 to 0.005 g/100 l, corresponding to the expansion of the bearing gap. In the animal experiment for 24 h, the plasma-free hemoglobin remained within normal ranges (<4.0 mg/dl). We confirmed that the hemolytic property of the pump was improved to the acceptable level by expanding the bearing gap greater than 60 μm.
