In vivo study of the performance of a mechanical seal involving a recirculating cooling water system used in a centrifugal blood pump

The integrity of the shaft seal is a critical factor in the success of an implantable centrifugal blood pump. A precision mechanical seal has been developed to address this requirement. The seal incorporates a recirculating cooling water system to provide lubrication and prevent deposition of blood elements. The objective of the current study was to experimentally evaluate the sealing properties of this mechanical seal in vivo. The leakage rate of plasma into the cooling water through the mechanical seal was measured by monitoring the infiltration of sodium ions from bovine blood. Measurement of the concentration of sodium ions was performed using inductively coupled plasma light emission analysis. The leakage rate of the cooling water into the blood through the mechanical seal was measured by monitoring the volume of the cooling water in the reservoir. Over a period of 153 days, the leakage rate of plasma was 0.022 ml/day and the leakage rate of the cooling water was 0.497 ml/day. In conclusion, the mechanical seal performed acceptably well to support its use in a centrifugal blood pump for chronic application.