Development of the next generation implantable pneumatic ventricular assist device for permanent use.

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The purpose of this work is to develop a next generation implantable pneumatic ventricular asist device(P-VAD) for permanent use. A diaphragm type blood pump for the implantable P-VAD has been developed. The mount angle of the inlet and outlet value affects the flow bahavior the blood pump and thrombus formation. The effect of the orifice direction of the inlet and outlet valve(ODIV, ODOV ; where direction toward the diaphragm-housing junction(DHJ) was defined as 0 degrees) was investigated by means of particle image velocimetry(PIV) visualization method. Monoleaflet mechanical valves(Medtronic-Hall Valve, (ρ23mm) was used. The observed flow velocity distribution was relatively low in the area between the inlet and outlet port roots, it was lowest(0.05m/s) at the 90 degrees ODIV. On the other hand, the flow velocity distribution in this area was highest(1.9m/s) at 135 degrees ODIV. Furthermore, the flow velocity of marginal area near the DHJ was relatively high at 135 degrees ODOV, and … More relatively low at 45 degree ODOV. The flow velocity in the proximal to the inlet port at 135 degrees ODOV(0.05m/s-0.65m/s) was always higher then that at 45 degrees ODOV(0.05m/s-0.22m/s) at any time of the beat cycle.The flow behavior inside the blood pump is significantly affected by the ODIV and ODOV, in terms of flow stagnation and thrombus formation.The cavitation which was generated with opening and closing of a valve causes erosion of the valve surface and hemolyzed blood. The effect of the valve orientation angle on a bileaflet mechanical heart valve(MHV) cavitations was investigated. A23mm Edwards MIRA bileaflet valve was used and the valve was rotated from o to 90 degrees on an inclined horizontal plane. The valve-closing motion was measured by means of a CCD laser displacement sensor. Images of MHV cavitation bubbles were recorded using a high-speed video camera. The contact delay time ranged from 0.88+/-0.41 to 0.50+/-0.27ms, and the time for the valve orientation angles of 0 and 30 degrees was longer than of the angle of 45, 60 and 90 degrees. The cavitation bubbles were caused by the first valve closure, valve rebound and the second valve closure, and were concentrated along the tip of the leaflet. The cavitation bubbles of the left side leaflet were caused by the first valve closure only at orientation angles of 45, 60, 90 degrees. The observation time of the cavitation bubbles caused by the first valve closure at 45, 60 and 90 degrees was longer that that of the bubbles caused by the valve rebound. The mechanism for the occurrence of MHV xcavitation differs from the valve closure motion. Valve orientation was found to affect the asynchronous closure motion of the two leaflet and the cavitation mechanism.Driveline infection is a serious major problem for the patients with an implantable VAD system. The novel percutaneous system to connect between an outer surface of percutaneous driveline and subcutaneous tissue was developed. This system mainly consists of porous segmented polyurethane with the three-dimensional reticulated structure which has tissue-like flexibility and sufficient mechanical strength. The test materials which inserted into the silicone tube implanted into subcutaneous tissue of an adult goat and tissue-compatibility of this material was investigated. The granulated tissue infiltrated into the test tube after 30 days implantation. Infiltrated tissue included the mature connective tissue, and did not include inflammatory or necrotic foci in the test tubes. The newly developed material has a sufficient ability to connect the percutanelus driveline and subcutaneous tissue in destination therapy with implantable VAD.A compact wearable pneumatic drive unit for ventricular assist device was developed. The drive unit consists of a brushless DC motor, a crankshaft, a cylinder piston, noncircular gears and air pressure regulation valves. Driving air pressure is generated by the cylinder piston. The noncircular gears generate the systolic ratio and the air pressure regulation valves limit the maximum and minimum pressure. The weight of the drive unit is approximately 1.8kg. The drive unit of 44% systolic ratio using a blood pump of 70mL stroke volume achieved more than 7L/min of pump output at 100bpm against after-load of 120mmHg in an overflow type mock circulation. The average electric power consumption varied from 8.6 to 17.7W with the beating rate and the after-load. The chronic animal tests using 2 Holstein calves weighing 62kg and 74kg with the drive units of 45 and 53% systolic ratio terminated on 30 and 39days without any malfunction. In the first animal test, the mean aortic pressures, bypass flows and electric power consumptions were maintained at 90+/-13mm Hg, 3.9+/-0.9L/min and 12+/-1W, respectively. In the second animal test, those values were maintained at 88+/-13mmHg, 5.0+/-0.5L/min and 16+/-2W. These results indicate that the newly developed drive unit has a potential to become a wearable drive unit. Less