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Research paper : Research and development of a monopivot centrifugal blood pump for clinical use (T. Yamane et al.)−19−Synthesiology - English edition Vol.5 No.1 (2012) holes, penetrating the impeller to recirculate the fluid in a pump and to prevent thrombus formation, because the fluid behind the centrifugal impeller would not exchange automatically. The results of flow visualization verified that washout holes should be concentrated to a single hole with a small area compared to separate large holes[3] (Fig. 2).Hemolysis testing using bovine blood revealed that the contact area governed the level of hemolysis; namely the smaller the contact area is, the lower the hemolysis level becomes[4] (Fig. 3).Based on these evidences of flow visualization experiments and hemolysis testing animal experiments were conducted at University of Tsukuba, and the results were verified. 3 Reset of the goal of development based on clinical needsWhen we were conducting animal experiments, a company, Senko Medical Instruments Mfg.Co.Ltd., joined the research collaboration. Generally medical device companies are often small/medium scale businesses, and they often join the development after animal experiments from the view point of risk management. Selecting AIST as a partner may be because the AIST team was not deeply connected to any companies then. Then the goal of development was switched from an implantable VAD of NEDO goal to a circulatory assist/extracorporeal pump for 4-week use based on the proposal of the company. The concept of monopivot centrifugal pump proposed by AIST was adopted for the product.Clinically available blood pumps for cardiac surgery and cardiac assist at present can be classified into four categories as follows:(1) Short term use (made of polymer, structure with seal, usable for 6 hours)The pharmaceutical price is around 60,000 yen and the total number of production is 40,000 in Japan.(2) Long term use (made of polymer, structure without seal, usable for 4 days)The pharmaceutical price is around 100,000 yen though insurance does not cover the open-heart surgery use.(3) Paracorporeal pulsatile VAD (placed outside the body, made of polyurethane, usable within a month)The pharmaceutical price is 3,160,000 yen though the durability proof is within a month.(4) Implantable VAD (made of Titanium, no limitation for period of use)The pharmaceutical price is 18,100,000 yen and the insurance covers for implantation.As an economic estimation, if an extracorporeal pump of 60,000 yen covers 25 % of the share of the market of 40,000 sales a year, the total sale would be 600,000,000 yen. In contrast, if an implantable VAD of 18,100,000 yen covers 50 % of the share of the market of 100 sales a year, the total sale would be 900,000,000 yen a year, which is almost the same as that of the extracorporeal pumps. Therefore, the former was selected as the goal of the development. The present pump features the cost of 60,000 yen and realizes a similar performance as the pneumatic VAD for one-month use of 3,160,000 yen. The goal of the product was set not only for surgical use but also for bridge-to-bridge use before long-term implanatble VAD, namely the performance is over (2) and the cost is (1).The product of the monopivot centrifugal pump is composed of an impeller of 50 mm in diameter with straight paths, a monopivot bearing of a 3 mm sphere made of stainless steel/ultrahigh molecular weight polyethylene, and a washout hole Fig. 2 Comparison of wash by washout hole through flow visualization for improvement of antithrombogenicityFlow VisualizationAnimal Experiment(d) 6 mm Hole(c)7 mm Hole(b) 8 mm Hole(a) 9 mm HoleImpeller Pivot Rear Casing Rear Casing Rear Casing Rear Casing Rear Casing Rear Casing Rear Casing Rear Casing Impeller Pivot Pivot Impeller Impeller Pivot φ50

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