Material of the Double Pivot Bearing System in the Gyro C1E3 Centrifugal Pump

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Abstract
A double pivot bearing system is adopted for the Gyro C1E3 centrifugal blood pump to achieve a completely sealless structure that prevents blood leakage and thrombus formation around the shaft. The double pivot bearing system is also a critical factor for blood trauma and durability of the C1E3 pump. This study focuses on the double pivot bearing material. The pump with the male ceramic and female polyethylene pivots (PE) was compared with the pump with the male ceramic and female ceramic pivots (CRM), pertaining to stability of the impeller spinning motion, hemolysis, and durability. At first, the wear rate of the pivots was recorded after operating the pumps in various rotational speeds. As for hemolysis, in vitro tests were carried out using fresh bovine blood in 2 conditions (5 L/min, 350 mm Hg and 5 L/min, 100 mm Hg). Then, stability of the spinning motion was investigated by evaluating the vibration of the pump. The two pumps with different female pivots were operated identically at 2,700 rpm, and the vibration signals were measured using an accelerometer that was mounted on the top of the pump housing. The following findings were obtained in this study. The wear sites were different between the PE and CRM. Most of the wear occurred at the top female polyethylene pivot in the PE. In contrast, most of the wear occurred at the top male ceramic pivot in the CRM. In addition, the amount of the initial wear was less and the wear rate was lower in the PE than in the CRM. The hemolysis caused by the PE was less than the hemolysis caused by the CRM. The vibration signals of the PE had less amplitude and a narrower range of frequency than the vibration signals of the CRM. In conclusion, the combination of materials male ceramic‐female polyethylene are superior to the male ceramic‐female ceramic for the double pivot bearing system of the Gyro C1E3 centrifugal pump because of less vibration, less hemolysis, and less wear.