Takashi Yamane

Tokyo University of Science, Edo, Tōkyō, Japan

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Publications (88)102.28 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have developed a hydrodynamically levitated centrifugal pump as a bridge-to-decision device. The purpose of the present study is to determine the optimal bearing gap of a multiarc radial bearing in the developed blood pump for the reduction of hemolysis. We prepared eight pump models having bearing gaps of 20, 30, 40, 80, 90, 100, 180, and 250 μm. The driving conditions were set to a pressure head of 200 mm Hg and a flow rate of 4 L/min. First, the orbital radius of the impeller was measured for the evaluation of the impeller stability. Second, the hemolytic property was evaluated in an in vitro hemolysis test. As a result, the orbital radius was not greater than 15 μm when the bearing gap was between 20 and 100 μm. The relative normalized index of hemolysis (NIH) ratios in comparison with BPX-80 were 37.67 (gap: 20 μm), 0.95 (gap: 30 μm), 0.96 (gap: 40 μm), 0.82 (gap: 80 μm), 0.77 (gap: 90 μm), 0.92 (gap: 100 μm), 2.76 (gap: 180 μm), and 2.78 (gap: 250 μm). The hemolysis tended to increase at bearing gaps of greater than 100 μm due to impeller instability. When the bearing gap decreased from 30 to 20 μm, the relative NIH ratios increased significantly from 0.95 to 37.67 times (P < 0.01) due to high shear stress. We confirmed that the optimal bearing gap was determined between 30 and 100 μm in the developed blood pump for the reduction of hemolysis.
    Artificial Organs 09/2014; 38(9). · 1.96 Impact Factor
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    ABSTRACT: The purpose of the present study is to establish an optimal design of the multi-arc hydrodynamic bearing in a centrifugal blood pump for the improvement of bearing stiffness and hemolysis level. The multi-arc bearing was designed to fulfill the required specifications: (i) ensuring the uniform bearing stiffness for various bearing angles; (ii) ensuring a higher bearing stiffness than the centrifugal force to prevent impeller whirl; and (iii) adjusting the bearing clearance as much as possible to reduce hemolysis. First, a numerical analysis was performed to optimize three design parameters of the multi-arc bearing: number of arcs N, bearing clearance C, and groove depth H. To validate the accuracy of the numerical analysis, the impeller trajectories for six pump models were measured. Finally, an in vitro hemolysis test was conducted to evaluate the hemolytic property of the multi-arc bearing. As a result of the numerical analysis, the optimal parameter combination was determined as follows: N = 4, C = 100 μm, and H ≥ 100 μm. In the measurements of the impeller trajectory, the optimal parameter combination was found to be as follows: N = 4, C = 90 μm, and H = 100 μm. This result demonstrated the high reliability of the numerical analysis. In the hemolysis test, the parameter combination that achieved the smallest hemolysis was obtained as follows: N = 4, C = 90 μm, and H = 100 μm. In conclusion, the multi-arc bearing could be optimized for the improvement of bearing stiffness and hemolysis level.
    Artificial Organs 08/2013; · 1.96 Impact Factor
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    ABSTRACT: A hydrodynamically levitated centrifugal blood pump with a semi-open impeller has been developed for mechanical circulatory assistance. However, a narrow bearing gap has the potential to cause hemolysis. The purpose of the present study is to optimize the geometric configuration of the hydrodynamic step bearing in order to reduce hemolysis by expansion of the bearing gap. First, a numerical analysis of the step bearing, based on lubrication theory, was performed to determine the optimal design. Second, in order to assess the accuracy of the numerical analysis, the hydrodynamic forces calculated in the numerical analysis were compared with those obtained in an actual measurement test using impellers having step lengths of 0%, 33%, and 67% of the vane length. Finally, a bearing gap measurement test and a hemolysis test were performed. As a result, the numerical analysis revealed that the hydrodynamic force was the largest when the step length was approximately 70%. The hydrodynamic force calculated in the numerical analysis was approximately equivalent to that obtained in the measurement test. In the measurement test and the hemolysis test, the blood pump having a step length of 67% achieved the maximum bearing gap and reduced hemolysis, as compared with the pumps having step lengths of 0% and 33%. It was confirmed that the numerical analysis of the step bearing was effective, and the developed blood pump having a step length of approximately 70% was found to be a suitable configuration for the reduction of hemolysis.
    Artificial Organs 07/2013; · 1.96 Impact Factor
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    ABSTRACT: The effect of a cutout on the pump pressure-flow characteristics and the impeller stability was quantified using computational fluid dynamics analysis in order to provide good hemocompatibility of the monopivot extracorporeal circulation pump. As a result, the following findings were clarified. The pump pressure is lower in the cutout model than in the no-cutout model. The impeller stability with respect to the buoyancy of the impeller is better in the cutout model than in the no-cutout model. The impeller stability with respect to the impeller tilt is better in the cutout model than in the no-cutout model. Therefore, the cutout model, in which the geometry corresponds to the commercialized pump, was likely to be better than the no-cutout model because the stability that has the possibility to decrease the gap instantaneously to increase hemolysis despite the impeller rotational speed slightly.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:2736-2739.
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    ABSTRACT: We have developed a hydrodynamically levitated centrifugal blood pump for extracorporeal circulatory support as a bridge to decision pump. The impeller is levitated using hydrodynamic bearings without any complicated control circuit or displacement sensor. However, the effect of the outer circumferential velocity and the bearing area on the hemolytic property has not been clarified, even if the bearing gap is same size. The purpose of this study is to experimentally evaluate the effect of the outer circumferential velocity and the bearing area in the bearing gaps on the hemolytic property in a hydrodynamically levitated centrifugal blood pump. We prepared three models for testing. These models have the same bearing gap size by adjusting the impeller levitation position. However, the outer circumferential velocity of the impeller and the bearing area in the minimum bearing gaps are different. The outer circumferential velocity of the impeller and the bearing area were assumed to be related to the maximum shear rate and the exposure time. For the evaluation, we conducted an impeller levitation performance test and an in vitro hemolysis test. As a result, the normalized index of hemolysis (NIH) was reduced from 0.084 g/100L to 0.040 g/100L corresponding to a reduction in the outer circumferential velocity and a reduction in the bearing area, even if the minimum bearing gaps were same size. We confirmed that, even if the bearing gap was same size under the stably levitated condition, the outer circumferential velocity and the bearing area should be decreased in order to improve the hemolytic property.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:2732-2735.
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    ABSTRACT: Monitoring of thrombogenic process is very important in ventricular assistance devices (VADs) used as temporary or permanent measures in patients with advanced heart failure. Currently, there is a lack of a system which can perform a real-time monitoring of thrombogenic activity. Electrical signals vary according to the change in concentration of coagulation factors as well as the distribution of blood cells, and thus have potential to detect the thrombogenic process in an early stage. In the present work, we have made an assessment of an instrumentation system exploiting the electrical properties of blood. The experiments were conducted using bovine blood. Electrical resistance tomography with eight-electrode sensor was used to monitor the spatio-temporal change in electrical resistivity of blood in thrombogenic and non-thrombogenic condition. Under non-thrombogenic condition, the resistivity was uniform across the cross-section and average resistivity monotonically decreased with time before remaining almost flat. In contrary, under thrombogenic condition, there was non-uniform distribution across the cross-section, and average resistivity fluctuated with time.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:4086-4089.
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    ABSTRACT: In order to monitor the condition of a patient using a left ventricular assist system (LVAS), blood flow should be measured. However, the reliable determination of blood-flow rate has not been established. The purpose of the present study is to develop a noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump. The flow meter uses the centrifugal force generated by the flow rate in the curved cannula. Two strain gauges served as sensors. The first gauges were attached to the curved area to measure static pressure and centrifugal force, and the second gauges were attached to straight area to measure static pressure. The flow rate was determined by the differences in output from the two gauges. The zero compensation was constructed based on the consideration that the flow rate could be estimated during the initial driving condition and the ventricular suction condition without using the flow meter. A mock circulation loop was constructed in order to evaluate the measurement performance of the developed flow meter with zero compensation. As a result, the zero compensation worked effectively for the initial calibration and the zero-drift of the measured flow rate. We confirmed that the developed flow meter using a curved cannula with zero compensation was able to accurately measure the flow rate continuously and noninvasively.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:4090-4093.
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    ABSTRACT: We have developed a hydrodynamically levitated centrifugal blood pump with a semi-open impeller for long-term circulatory assist. The pump uses hydrodynamic bearings to enhance durability and reliability without additional displacement-sensors or control circuits. However, a narrow bearing gap of the pump has a potential for hemolysis. The purpose of this study is to develop the hydrodynamically levitated centrifugal blood pump with a semi-open impeller, and to evaluate the effect of a bearing gap on hemolytic property. The impeller levitates using a spiral-groove type thrust bearing, and a herringbone-groove type radial bearing. The pump design was improved by adopting a step type thrust bearing and optimizing the pull-up magnetic force. The pump performance was evaluated by a levitation performance test, a hemolysis test and an animal experiment. In these tests, the bearing gap increased from 1 to 63 μm. In addition, the normalized index of hemolysis (NIH) improved from 0.415 to 0.005 g/100 l, corresponding to the expansion of the bearing gap. In the animal experiment for 24 h, the plasma-free hemoglobin remained within normal ranges (<4.0 mg/dl). We confirmed that the hemolytic property of the pump was improved to the acceptable level by expanding the bearing gap greater than 60 μm.
    Bio-medical materials and engineering 01/2013; 23(1):37-47. · 1.09 Impact Factor
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    ABSTRACT: The hemocompatibility for the recently approved ventricular assist device EVAHEART(®) was examined through flow visualization with a 300 % scale-up model. The absence of flow separations around the centrifugal vanes indicated that the curvature of the open vanes was suitable. The flow in the vane-shaft clearance was found to effectively produce sufficient shear stresses along the stationary shaft surface. The hemocompatibility was verified for a wide range of flow conditions.
    Journal of Artificial Organs 10/2012; · 1.41 Impact Factor
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    ABSTRACT: The MERA monopivot centrifugal pump has been developed for use in open-heart surgery, circulatory support, and bridge-to-decision for up to 4 weeks. The pump has a closed-type, 50-mm diameter impeller with four straight paths. The impeller is supported by a monopivot bearing and is driven by a radial-flux magnet-coupling motor. Because flow visualization experiments have clarified sufficient pivot wash and stagnation at the sharp corner of the pivot support was suggested, sharp corners were removed in the design stage. The index of hemolysis of the pump operating at more than 200 mm Hg was found to be lower than that of a commercial pump. Four-week animal tests were then conducted two times; improvement of thrombus formation was seen in the female pivot through modification of female pivot geometry. Overall antithrombogenicity was also recorded. Finally, to assure mid-term use, an additional 4-week durability test revealed that the rate of the axial pivot wear was as small as 1.1 µm/day. The present in vitro and in vivo studies revealed that the MERA monopivot centrifugal pump has sufficient hemocompatibility and durability for up to 4 weeks.
    Artificial Organs 09/2012; · 1.96 Impact Factor
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    ABSTRACT: A centrifugal blood pump for artificial heart has to have low hemolysis and no thrombus formation. For finding and removing the fluid dynamic causes of the above mentioned phenomena, flow visualization was utilized, as flow visualization can identify the high shear and stagnation locations which relate to hemolysis and thrombus formation respectively. In the present paper, general fluid dynamic characteristics of centrifugal blood pumps will be extracted, through analyzing four typical centrifugal pumps with flow visualization technique. Finding shear in the volute and diffuser regions, confirming vortex formation at washout holes, and quantitative analysis of the flow in the inlet regions are the shown examples. The obtained results correspond well to hemolysis tests, which proves that flow visualization is a useful tool in developing and analyzing blood pumps for artificial hearts. Keywordsflow visualization-particle tracking velocimetry-centrifugal blood pump-shear evaluation-artificial heart IndexEvaluation of shear and recirculation in artificial heart
    Journal of Visualization 04/2012; 3(1):79-92. · 0.51 Impact Factor
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    ABSTRACT: Blood flow should be measured to monitor conditions of patients with implantable artificial hearts continuously and noninvasively. We have developed a noninvasive miniaturized mass-flow meter using a curved cannula for an axial flow blood pump. The mass-flow meter utilized centrifugal force generated by the mass-flow rate in the curved cannula. Two strain gauges served as sensors. Based on the numerical analysis, the first gauge, attached to the curved area, measured static pressure and centrifugal force, and the second, attached to the straight area, measured static pressure for static pressure compensation. The mass-flow rate was determined by the differences in output from the two gauges. To compensate for the inertia force under the pulsatile flow, a 0.75-Hz low-pass filter was added to the electrical circuit. In the evaluation tests, numerical analysis and an actual measurement test using bovine blood were performed to evaluate the measurement performances. As a result, in the numerical analysis, the relationship between the differential pressure caused by centrifugal force and the flow rate was verified. In the actual measurement test, measurement error was less than ± 0.5 L/min, and the time delay was 0.12 s. We confirmed that the developed mass-flow meter was able to measure mass-flow rate continuously and noninvasively.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:1343-6.
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    ABSTRACT: We have developed a hydrodynamic levitation centrifugal blood pump with a semi-open impeller for a mechanically circulatory assist. The impeller levitated with original hydrodynamic bearings without any complicated control and sensors. However, narrow bearing gap has the potential for causing hemolysis. The purpose of the study is to investigate the geometric configuration of the hydrodynamic step bearing to minimize hemolysis by expansion of the bearing gap. Firstly, we performed the numerical analysis of the step bearing based on Reynolds equation, and measured the actual hydrodynamic force of the step bearing. Secondly, the bearing gap measurement test and the hemolysis test were performed to the blood pumps, whose step length were 0 %, 33 % and 67 % of the vane length respectively. As a result, in the numerical analysis, the hydrodynamic force was the largest, when the step bearing was around 70 %. In the actual evaluation tests, the blood pump having step 67 % obtained the maximum bearing gap, and was able to improve the hemolysis, compared to those having step 0% and 33%. We confirmed that the numerical analysis of the step bearing worked effectively, and the blood pump having step 67 % was suitable configuration to minimize hemolysis, because it realized the largest bearing gap.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:1331-4.
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    ABSTRACT: In order to monitor the condition of patients with implantable left ventricular assist systems (LVAS), it is important to measure pump flow rate continuously and noninvasively. However, it is difficult to measure the pump flow rate, especially in an implantable axial flow blood pump, because the power consumption has neither linearity nor uniqueness with regard to the pump flow rate. In this study, a miniaturized mass-flow meter for discharged patients with an implantable axial blood pump was developed on the basis of computational analysis, and was evaluated in in-vitro tests. The mass-flow meter makes use of centrifugal force produced by the mass-flow rate around a curved cannula. An optimized design was investigated by use of computational fluid dynamics (CFD) analysis. On the basis of the computational analysis, a miniaturized mass-flow meter made of titanium alloy was developed. A strain gauge was adopted as a sensor element. The first strain gauge, attached to the curved area, measured both static pressure and centrifugal force. The second strain gauge, attached to the straight area, measured static pressure. By subtracting the output of the second strain gauge from the output of the first strain gauge, the mass-flow rate was determined. In in-vitro tests using a model circulation loop, the mass-flow meter was compared with a conventional flow meter. Measurement error was less than ±0.5 L/min and average time delay was 0.14 s. We confirmed that the miniaturized mass-flow meter could accurately measure the mass-flow rate continuously and noninvasively.
    Journal of Artificial Organs 05/2011; 14(3):178-84. · 1.41 Impact Factor
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    ABSTRACT: To facilitate research and development (R&D) and to expedite the review processes of medical devices, the Ministry of Health, Labor and Welfare (MHLW) and the Ministry of Economy, Trade and Industry (METI) founded a joint committee to establish guidance for newly emerging technology. From 2005 to 2007, two working groups held discussions on ventricular assist devices and total artificial hearts, including out-of-hospital programs, based on previous guidance documents and standards. Based on this discussion, the METI published the R&D Guidelines for innovative artificial hearts in 2007, and in 2008 the MHLW published a Notification by Director regarding the evaluation criteria for emerging technology.
    Artificial Organs 09/2010; 34(9):699-702. · 1.96 Impact Factor
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    ABSTRACT: To grasp conditions of patients and implantable artificial hearts, it is important to measure the pump flow rate continuously and noninvasively. In this study, a miniaturized mass-flow meter for discharged patients with an implantable axial flow blood pump was developed. The mass-flow meter makes use of centrifugal force generated by mass-flow rate around the curved cannula. Based on the computational fluid dynamics (CFD) analysis, the prototype miniaturized mass-flow meter was developed. Two strain gauges were adopted as the sensor elements. The first strain gauge, attached to the straight area, measured static pressure. The second strain gauge, attached to the curved area, measured static pressure and the centrifugal force. By subtracting the output of the first strain gauge from the output of the second strain gauge, the mass-flow rate was determined. In the evaluation tests using the mock-up circulation loop, the mass-flow meter was compared to a commercial flow meter. As a result, measurement error was less than 1.0 L/min, and time delay was less than 0.2 s. We confirmed that the miniaturized mass-flow meter could accurately measure the mass-flow rate continuously and noninvasively.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:2513-6.
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    ABSTRACT: We have developed a noncontact-type centrifugal blood pump with hydrodynamic bearings and a semi-open impeller for mechanical circulatory assist. The impeller is levitated by an original spiral-groove thrust bearing and a herringbone-groove journal bearing, without any additional displacement-sensing module or additional complex control circuits. The pump was improved by optimizing the groove direction of the spiral-groove thrust bearing and the pull-up magnetic force between the rotor magnet and the stator coil against the impeller. To evaluate hemocompatibility, we conducted a levitation performance test and in vitro hemocompatibility tests by means of a mock-up circulation loop. In the hemolysis test, the normalized index of hemolysis was reduced from 0.721 to 0.0335 g/100 L corresponding to an expansion of the bearing gap from 1.1 to 56.1 microm. In the in vitro antithrombogenic test, blood pumps with a wide thrust bearing gap were effective in preventing thrombus formation. Through in vitro evaluation tests, we confirmed that hemocompatibility was improved by balancing the hydrodynamic fluid dynamics and magnetic forces.
    Artificial Organs 08/2009; 33(10):798-804. · 1.96 Impact Factor
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    ABSTRACT: We developed a simple in vitro antithrombogenic testing method using a mock circulation system as used in the hemolysis tests to evaluate the antithrombogenicity of centrifugal blood pumps. This method was not designed to substitute for animal experiments but was intended to be a screening test method for selecting pumps robust enough to operate properly during animal experiments. In this study, we were able to maintain an almost constant activated clotting time for test blood for 10 hours by using both trisodium citrate and calcium chloride. We carried out the in vitro antithrombogenic testing of monopivot type centrifugal blood pumps (models DD3 and DD6) and hydrodynamic bearing pumps (models HH2 and HH7), which were developed at Advanced Industrial Science and Technology. Thrombus formation was not observed in the DD3 or DD6 pumps but occurred in the HH2 and HH7 pumps. The HH2 pump generated thrombi during a 1.5-hour ex vivo test, and the test was terminated. We expect this in vitro testing method to be useful for undertaking evaluations before animal experiments.
    ASAIO journal (American Society for Artificial Internal Organs: 1992) 06/2009; 55(4):314-22. · 1.39 Impact Factor
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    ABSTRACT: The hemocompatibility of a newly developed monopivot circulatory assist pump was evaluated by the computational fluid dynamic (CFD) analyses with the particle tracking velocimetry measurement. Results were compared with those of the hemolysis test and in vitro antithrombogenic test to prevent hemolysis and thrombus formation inside the pump. The results of the CFD analysis and the particle tracking velocimetry had a good agreement with each other. The flow distributions by the CFD analysis indicated that the radial jet out of the impeller was adequately weak so that the wall shear stress was lower than 300 Pa on the volute casing wall. It corresponded with the hemolysis tests results, indicating that the hemolysis level was lower than that of the commercially available pump. However, the flow distributions also indicated that the pivot that was easy to stagnate was washed out, not only by the secondary flow through the back gap of the impeller, but also by the vortices generated by the secondary vanes. It corresponded with the in vitro antithrombogenic test results, indicating that thrombus formation could be removed only by redesigning the geometry of the secondary vanes.
    Artificial Organs 05/2009; 33(4):378-86. · 1.96 Impact Factor
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    ABSTRACT: As for artificial hearts generally used in short term, thrombus formation is still a serious issue. To realize effective medical treatment for patients with the artificial heart without increase of anticoagulant agent, it is essential to detect and even predict thrombus formations. The purpose of this study is to develop a noninvasive thrombus detection system for artificial hearts. Considering the difference from the optical characteristics of both thrombus and blood, we have developed a thrombus detection system with a near-infrared (NIR) laser and a photomultiplier. This developed system is composed of a light-emitting device with NIR laser (805 nm), a light receiver with photomultiplier for high measurement accuracy, and a thrombus detection algorithm based on probability statistics. This system is generally attached outside the tubing of the extracorporeal circuit. To confirm the effectiveness of this system, we performed a thrombus detection test by using this system (light intensity of 2 mW and light path of 6 mm) in the mock circulation loop consisting of the reservoir, the Tygon tubing, and a centrifugal blood pump with hydrodynamic bearings. This circulation loop was filled with sheep whole blood including acid-citratedextrose solution. When we intentionally generated thrombus by adjusting activated coagulation time with CaCl2, this thrombus detection system continuously detected floating thrombus, which seemed to be generated around the pump impeller and be moved from there. Moreover this system might have indicated prediction associated with a blood condition conductive to thrombus formation before the thrombus formation was supposed to be generated around the impeller. In conclusion, we have confirmed the developed thrombus detection system has enough performance to detect floating thrombus and may have the possibility to detect early stages of thrombus formation in the artificial hearts.
    12/2008: pages 635-638;

Publication Stats

455 Citations
102.28 Total Impact Points

Institutions

  • 2013
    • Tokyo University of Science
      Edo, Tōkyō, Japan
  • 2002–2013
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan
  • 2012
    • Tokyo University of Science, Suwa
      Kamisuwa, Nagano, Japan
  • 1999–2008
    • University of Tsukuba
      • Institute of Clinical Medicine
      Tsukuba, Ibaraki, Japan
  • 2005
    • Tokyo Medical and Dental University
      • Department of Artificial Organs
      Edo, Tōkyō, Japan
  • 1999–2000
    • Ibaraki University
      • Department of Mechanical Engineering
      Mito-shi, Ibaraki-ken, Japan
  • 1998
    • National Cerebral and Cardiovascular Center
      • Department of Cardiovascular Medicine
      Ōsaka, Ōsaka, Japan