体外循環用ボール弁の開発

抄録

As a prosthetic heart valve for the pulsatile extracorporeal assist device, a ducted ball valve has been developed. A conventional ball valve, compared with disc- or leaflet valve, is rather simple in structure, but high in pressure loss. This poor hydrodynamic property is caused by its small valve-seat orifice and the generation of disturbed wake vortex. However, if the ball is installed in a well-contoured duct, the pressure loss is supposed to be much reduced.
So, we made three kinds of contour of the duct including a semi-straight tube. In a non-pulsatile flow, the pressure loss was measured and the flow pattern in the wake region of the ball was visualized by a dye tracer. Further, in a pulse duplicator, the flow rate, the pressure at the inlet and outlet of the valve, and the movement of the ball were observed.
The contour (type (C)), along which the pressure (velocity) is to be constsnt, was the most favorable; it proved to have the lowest pressure loss, the narrowest vortex region, the lowest regurgitant flow, and the most stable movement of the ball.
Therefore, this valve was chosen to compare with a Bjork-Shiely valve and a St.Jude Medical valve in a non-pulsatile flow and a pulse duplicator. This ducted ball valve proved to be as low in pressure loss as the SJM valve. And the regurgitant flow during the valve closing period and the impulsive pressure induced by water hammer effect at the instant of valve closure were both the lowest.
In conclusions, the ball valve installed in the well-contoured duct proved to have an excellent hydrodynamic performance. Therefore, this ducted ball valve may be expected to take the place of the present disc- and leafletvalves as a prosthetic valve for pulsatile extracorporeal assist device.