[A cone shaped one-way valve for an extracorporeal bypass circuit]

For an extracorporeal circulation, either a unidirectional pump or a one-way valve is required. Most of the one-way valves developed so far for a cardiac valve operation have excellent rheological features. But, they are too expensive to be thrown away after a short usage in a disposable bypass circuit. Though a ball valve is simple to make and not expensive, the spherical float inside the valve causes a turbulence in the down stream. This turbulence in the blood stream will become a cause of hematological side effects during the extracorporeal circulation. To prevent this turbulence, we designed a cone shape float with a hemispherical head and a tapered tail. The valve chamber was also changed to a similar shape with a diameter 4 mm larger than that of the float. Three small notch-like spacers were made near the head of the float to prevent wedging of the float into the cone shape region of the valve chamber. Water passed through the valve with a laminar flow without much resistance. Regurgitation at the valve by reversing pressure was insignificant. But, the valve sometimes fell into dysfunction suddenly. Observation with a videocamera revealed that the float often began a long axis rotation and tail swung in the flow. Then the valve suddenly fell in to dysfunction due to the oblique fixation of the float in the valve chamber. A gentle knock of the valve could resume the valve function. However, the cone shaped valve will not be suitable for an extracorporeal life support system where any hazard must be avoided.