The Experts below are selected from a list of 1536 Experts worldwide ranked by ideXlab platform

Takashi Yamane - One of the best experts on this subject based on the ideXlab platform.

  • Improvement of hemolysis performance in a hydrodynamically levitated Centrifugal Blood Pump by optimizing a shroud size
    Journal of Artificial Organs, 2021
    Co-Authors: Ryo Kosaka, Osamu Maruyama, Masahiro Nishida, Daisuke Sakota, Takashi Yamane
    Abstract:

    We have developed a hydrodynamically levitated Centrifugal Blood Pump. In the Blood Pump having hydrodynamic bearings, the narrow bearing gap has a potential for high hemolysis. The purpose of the this study is to improve hemolysis performance in a hydrodynamically levitated Centrifugal Blood Pump by optimizing a shroud size. The impeller was levitated passively at the position where the thrust forces acting on the impeller were balanced. We focused on a size of a bottom shroud with a hydrodynamic bearing that could change the bottom hydrodynamic force to balance the thrust force at the wide bearing gap for reducing hemolysis. Five test models with various shroud size were compared: 989 mm^2 (HH-10.5), 962 mm^2 (HH-12), 932 mm^2 (HH-13.5), 874 mm^2 (HH-16), and 821 mm^2 (HH-18). A numerical analysis was first performed to estimate the bearing gaps in the test model. The bearing gaps were then measured to validate the numerical analysis. Finally, an in vitro hemolysis test was performed. The numerical analysis revealed that the HH-13.5 model had the widest bearing gap of 129 µm. In the measurement test, the estimation error for the bearing gap was less than 10%. In the hemolysis test, the HH-13.5 model achieved the lowest hemolysis level among the five models. The present study demonstrated that the numerical analysis was found to be effective for determining the optimal should size, and the HH-13.5 model had the optimal shroud size in the developed hydrodynamically levitated Centrifugal Blood Pump to reduce hemolysis.

  • Plasma Skimming in a Spiral Groove Bearing of a Centrifugal Blood Pump
    Artificial organs, 2016
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    Plasma skimming is a phenomenon in which discharge hematocrit is lower than feed hematocrit in microvessels. Plasma skimming has been investigated at a bearing gap in a spiral groove bearing (SGB), as this has the potential to prevent hemolysis in the SGB of a Blood Pump. However, it is not clear whether plasma skimming occurs in a Blood Pump with the SGB, because the hematocrit has not been obtained. The purpose of this study is to verify plasma skimming in an SGB of a Centrifugal Blood Pump by developing a hematocrit measurement method in an SGB. Erythrocyte observation using a high-speed microscope and a bearing gap measurement using a laser confocal displacement meter was performed five times. In these tests, bovine Blood as a working fluid was diluted with autologous plasma to adjust the hematocrit to 1.0%. A resistor was adjusted to achieve a pressure head of 100 mm Hg and a flow rate of 5.0 L/min at a rotational speed of 2800 rpm. Hematocrit on the ridge region in the SGB was measured using an image analysis based on motion image of erythrocytes, mean corpuscular volume, the measured bearing gap, and a cross-sectional area of erythrocyte. Mean hematocrit on the ridge region in the SGB was linearly reduced from 0.97 to 0.07% with the decreasing mean bearing gap from 38 to 21 μm when the rotational speed was changed from 2250 to 3000 rpm. A maximum plasma skimming efficiency of 93% was obtained with a gap of 21 μm. In conclusion, we succeeded in measuring the hematocrit on the ridge region in the SGB of the Blood Pump. Hematocrit decreased on the ridge region in the SGB and plasma skimming occurred with a bearing gap of less than 30 μm in the hydrodynamically levitated Centrifugal Blood Pump.

  • Evaluation of a Spiral Groove Geometry for Improvement of Hemolysis Level in a Hydrodynamically Levitated Centrifugal Blood Pump
    Artificial organs, 2015
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    The purpose of this study is to evaluate a spiral groove geometry for a thrust bearing to improve the hemolysis level in a hydrodynamically levitated Centrifugal Blood Pump. We compared three geometric models: (i) the groove width is the same as the ridge width at any given polar coordinate (conventional model); (ii) the groove width contracts inward from 9.7 to 0.5 mm (contraction model); and (iii) the groove width expands inward from 0.5 to 4.2 mm (expansion model). To evaluate the hemolysis level, an impeller levitation performance test and in vitro hemolysis test were conducted using a mock circulation loop. In these tests, the driving conditions were set at a pressure head of 200 mm Hg and a flow rate of 4.0 L/min. As a result of the impeller levitation performance test, the bottom bearing gaps of the contraction and conventional models were 88 and 25 μm, respectively. The impeller of the expansion model touched the bottom housing. In the hemolysis test, the relative normalized index of hemolysis (NIH) ratios of the contraction model in comparison with BPX-80 and HPM-15 were 0.6 and 0.9, respectively. In contrast, the relative NIH ratios of the conventional model in comparison with BPX-80 and HPM-15 were 9.6 and 13.7, respectively. We confirmed that the contraction model achieved a large bearing gap and improved the hemolysis level in a hydrodynamically levitated Centrifugal Blood Pump.

  • EMBC - Evaluation of erythrocyte flow at a bearing gap in a hydrodynamically levitated Centrifugal Blood Pump
    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2015
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    We have developed a hydrodynamically levitated Centrifugal Blood Pump for extracorporeal circulatory support. In the Blood Pump, a spiral groove bearing was adopted for a thrust bearing. In the spiral groove bearing, separation of erythrocytes and plasma by plasma skimming has been postulated to occur. However, it is not clarified that plasma skimming occurs in a spiral groove bearing. The purpose of this study is to verify whether plasma skimming occurs in the spiral groove bearing of a hydrodynamically levitated Centrifugal Blood Pump. For evaluation of plasma skimming in the spiral groove bearing, an impeller levitation performance test using a laser focus displacement meter and a microscopic visualization test of erythrocyte flow using a high-speed microscope were conducted. Bovine Blood diluted with autologous plasma to adjust hematocrit to 1.0% was used as a working fluid. Hematocrit on the ridge region in the spiral groove bearing was estimated using image analysis. As a result, hematocrits on the ridge region with gaps of 45 µm, 31 µm, and 25 µm were calculated as 1.0%, 0.6%, and 0.3%, respectively. Maximum skimming efficiency in this study was calculated as 70% with a gap of 25 µm. We confirmed that separation of erythrocyte and plasma occurred in the spiral groove bearing with decrease in bearing gap in a hydrodynamically levitated Centrifugal Blood Pump.

  • EMBC - Fluid dynamic design for low hemolysis in a hydrodynamically levitated Centrifugal Blood Pump
    Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and, 2013
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Katsuyuki Kuwana, Osamu Maruyama, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi
    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.

Masahiro Nishida - One of the best experts on this subject based on the ideXlab platform.

  • Improvement of hemolysis performance in a hydrodynamically levitated Centrifugal Blood Pump by optimizing a shroud size
    Journal of Artificial Organs, 2021
    Co-Authors: Ryo Kosaka, Osamu Maruyama, Masahiro Nishida, Daisuke Sakota, Takashi Yamane
    Abstract:

    We have developed a hydrodynamically levitated Centrifugal Blood Pump. In the Blood Pump having hydrodynamic bearings, the narrow bearing gap has a potential for high hemolysis. The purpose of the this study is to improve hemolysis performance in a hydrodynamically levitated Centrifugal Blood Pump by optimizing a shroud size. The impeller was levitated passively at the position where the thrust forces acting on the impeller were balanced. We focused on a size of a bottom shroud with a hydrodynamic bearing that could change the bottom hydrodynamic force to balance the thrust force at the wide bearing gap for reducing hemolysis. Five test models with various shroud size were compared: 989 mm^2 (HH-10.5), 962 mm^2 (HH-12), 932 mm^2 (HH-13.5), 874 mm^2 (HH-16), and 821 mm^2 (HH-18). A numerical analysis was first performed to estimate the bearing gaps in the test model. The bearing gaps were then measured to validate the numerical analysis. Finally, an in vitro hemolysis test was performed. The numerical analysis revealed that the HH-13.5 model had the widest bearing gap of 129 µm. In the measurement test, the estimation error for the bearing gap was less than 10%. In the hemolysis test, the HH-13.5 model achieved the lowest hemolysis level among the five models. The present study demonstrated that the numerical analysis was found to be effective for determining the optimal should size, and the HH-13.5 model had the optimal shroud size in the developed hydrodynamically levitated Centrifugal Blood Pump to reduce hemolysis.

  • Plasma Skimming in a Spiral Groove Bearing of a Centrifugal Blood Pump
    Artificial organs, 2016
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    Plasma skimming is a phenomenon in which discharge hematocrit is lower than feed hematocrit in microvessels. Plasma skimming has been investigated at a bearing gap in a spiral groove bearing (SGB), as this has the potential to prevent hemolysis in the SGB of a Blood Pump. However, it is not clear whether plasma skimming occurs in a Blood Pump with the SGB, because the hematocrit has not been obtained. The purpose of this study is to verify plasma skimming in an SGB of a Centrifugal Blood Pump by developing a hematocrit measurement method in an SGB. Erythrocyte observation using a high-speed microscope and a bearing gap measurement using a laser confocal displacement meter was performed five times. In these tests, bovine Blood as a working fluid was diluted with autologous plasma to adjust the hematocrit to 1.0%. A resistor was adjusted to achieve a pressure head of 100 mm Hg and a flow rate of 5.0 L/min at a rotational speed of 2800 rpm. Hematocrit on the ridge region in the SGB was measured using an image analysis based on motion image of erythrocytes, mean corpuscular volume, the measured bearing gap, and a cross-sectional area of erythrocyte. Mean hematocrit on the ridge region in the SGB was linearly reduced from 0.97 to 0.07% with the decreasing mean bearing gap from 38 to 21 μm when the rotational speed was changed from 2250 to 3000 rpm. A maximum plasma skimming efficiency of 93% was obtained with a gap of 21 μm. In conclusion, we succeeded in measuring the hematocrit on the ridge region in the SGB of the Blood Pump. Hematocrit decreased on the ridge region in the SGB and plasma skimming occurred with a bearing gap of less than 30 μm in the hydrodynamically levitated Centrifugal Blood Pump.

  • Evaluation of a Spiral Groove Geometry for Improvement of Hemolysis Level in a Hydrodynamically Levitated Centrifugal Blood Pump
    Artificial organs, 2015
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    The purpose of this study is to evaluate a spiral groove geometry for a thrust bearing to improve the hemolysis level in a hydrodynamically levitated Centrifugal Blood Pump. We compared three geometric models: (i) the groove width is the same as the ridge width at any given polar coordinate (conventional model); (ii) the groove width contracts inward from 9.7 to 0.5 mm (contraction model); and (iii) the groove width expands inward from 0.5 to 4.2 mm (expansion model). To evaluate the hemolysis level, an impeller levitation performance test and in vitro hemolysis test were conducted using a mock circulation loop. In these tests, the driving conditions were set at a pressure head of 200 mm Hg and a flow rate of 4.0 L/min. As a result of the impeller levitation performance test, the bottom bearing gaps of the contraction and conventional models were 88 and 25 μm, respectively. The impeller of the expansion model touched the bottom housing. In the hemolysis test, the relative normalized index of hemolysis (NIH) ratios of the contraction model in comparison with BPX-80 and HPM-15 were 0.6 and 0.9, respectively. In contrast, the relative NIH ratios of the conventional model in comparison with BPX-80 and HPM-15 were 9.6 and 13.7, respectively. We confirmed that the contraction model achieved a large bearing gap and improved the hemolysis level in a hydrodynamically levitated Centrifugal Blood Pump.

  • EMBC - Evaluation of erythrocyte flow at a bearing gap in a hydrodynamically levitated Centrifugal Blood Pump
    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2015
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi, Daisuke Sakota, Osamu Maruyama
    Abstract:

    We have developed a hydrodynamically levitated Centrifugal Blood Pump for extracorporeal circulatory support. In the Blood Pump, a spiral groove bearing was adopted for a thrust bearing. In the spiral groove bearing, separation of erythrocytes and plasma by plasma skimming has been postulated to occur. However, it is not clarified that plasma skimming occurs in a spiral groove bearing. The purpose of this study is to verify whether plasma skimming occurs in the spiral groove bearing of a hydrodynamically levitated Centrifugal Blood Pump. For evaluation of plasma skimming in the spiral groove bearing, an impeller levitation performance test using a laser focus displacement meter and a microscopic visualization test of erythrocyte flow using a high-speed microscope were conducted. Bovine Blood diluted with autologous plasma to adjust hematocrit to 1.0% was used as a working fluid. Hematocrit on the ridge region in the spiral groove bearing was estimated using image analysis. As a result, hematocrits on the ridge region with gaps of 45 µm, 31 µm, and 25 µm were calculated as 1.0%, 0.6%, and 0.3%, respectively. Maximum skimming efficiency in this study was calculated as 70% with a gap of 25 µm. We confirmed that separation of erythrocyte and plasma occurred in the spiral groove bearing with decrease in bearing gap in a hydrodynamically levitated Centrifugal Blood Pump.

  • EMBC - Fluid dynamic design for low hemolysis in a hydrodynamically levitated Centrifugal Blood Pump
    Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and, 2013
    Co-Authors: Tomotaka Murashige, Ryo Kosaka, Katsuyuki Kuwana, Osamu Maruyama, Takashi Yamane, Masahiro Nishida, Yasuo Kawaguchi
    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.

Yukihiko Nosé - One of the best experts on this subject based on the ideXlab platform.

  • Mapping of Pump Efficiency on the Pressure‐Flow Curve of a Centrifugal Blood Pump
    Artificial Organs, 2008
    Co-Authors: Yoshiyuki Takami, Tadashi Nakazawa, Kenzo Makinouchi, Julie Glueck, Robert Benkowski, Yukihiko Nosé
    Abstract:

    : Because Pump efficiency is closely related to heat generation and Blood trauma in a Centrifugal Blood Pump, it is quite important to study Pump efficiencies in a variety of conditions. In the present study, Pump efficiencies were mapped on the pressure head-flow rate curves of 4 different Pumps; Bio Medicus Bio Pump (BP-80), Nikkiso (NK), Gyro C1E3, and Gyro PI601 (diameter of the impeller, NK: 50 mm, ClE3: 65 mm, and PI601: 50 mm). The mapping of Pump efficiency revealed the following findings. First, the cone type (BP-80) has less Pump efficiency than the impeller type (NK and ClE3); second, the miniaturization of the C1E3 to the PI601 has resulted in an increase in Pump efficiency; and third, the diameter of the impeller may contribute to the Pump efficiency of an impeller type Pump. The mapping of the Pump efficiency, as demonstrated in this study, is useful for the analysis of hydraulic Pump performance in a wide range of clinically applied conditions.

  • mapping of Pump efficiency on the pressure flow curve of a Centrifugal Blood Pump
    Artificial Organs, 2008
    Co-Authors: Yoshiyuki Takami, Tadashi Nakazawa, Kenzo Makinouchi, Julie Glueck, Robert Benkowski, Yukihiko Nosé
    Abstract:

    : Because Pump efficiency is closely related to heat generation and Blood trauma in a Centrifugal Blood Pump, it is quite important to study Pump efficiencies in a variety of conditions. In the present study, Pump efficiencies were mapped on the pressure head-flow rate curves of 4 different Pumps; Bio Medicus Bio Pump (BP-80), Nikkiso (NK), Gyro C1E3, and Gyro PI601 (diameter of the impeller, NK: 50 mm, ClE3: 65 mm, and PI601: 50 mm). The mapping of Pump efficiency revealed the following findings. First, the cone type (BP-80) has less Pump efficiency than the impeller type (NK and ClE3); second, the miniaturization of the C1E3 to the PI601 has resulted in an increase in Pump efficiency; and third, the diameter of the impeller may contribute to the Pump efficiency of an impeller type Pump. The mapping of the Pump efficiency, as demonstrated in this study, is useful for the analysis of hydraulic Pump performance in a wide range of clinically applied conditions.

  • The fourth-generation Centrifugal Blood Pump
    Journal of Artificial Organs, 2002
    Co-Authors: Seiji Ichikawa, Kuniyoshi Watanabe, Yukihiko Nosé
    Abstract:

    The NEDO Gyro permanently implantable (PI) Centrifugal Blood Pump has been developed as a simple, durable, Centrifugal Blood Pump without a complex magnetic suspension system. In vitro studies were performed using a Gyro PI Pump with the transparent Pump housing in a mock circuit. These studies revealed that the impeller transfers to a floating or a top contact condition, which was dependent on the revolutions per minute (RPM). This Pump can be easily converted from a left ventricular assist device (LVAD) to a right ventricular assist device (RVAD) by simply adding a spacer between the Pump and the actuator. In order to optimize the impeller suspension for the LVAD and RVAD, spacers of the proper thickness are inserted between both of the Pumps and the actuators to regulate the magnetic force. Two Gyro PI Pumps were implanted in a bovine model in a 3-month biventricular assist device (BVAD) animal study. This experiment was electively terminated 90 days after implantation. All of the parameters, including Pump flow rate, power consumption, and plasma free hemoglobin, were in acceptable ranges. No thrombus formation was observed in either Pump. Antithrombogenesis and effectiveness were demonstrated in this animal study. The NEDO Gyro PI Pump is ready to move on to the 3-month preclinical system evaluation.

  • Biocompatibility of alumina ceramic and polyethylene as materials for pivot bearings of a Centrifugal Blood Pump.
    Journal of biomedical materials research, 1997
    Co-Authors: Yoshiyuki Takami, Tadashi Nakazawa, Kenzo Makinouchi, Julie Glueck, Yukihiko Nosé
    Abstract:

    The double pivot bearings in the Gyro C1E3 Centrifugal Blood Pump incorporate a high-purity alumina (Al2O3) ceramic and an ultra-high-molecular-weight polyethylene (UHMWPE). This Centrifugal Pump has been developed as a completely sealless Pump for long-term usage. The combination of Al2O3 and UHMWPE are the materials of choice for the acetabular bearing in artificial joints, which have proven to be clinically reliable for over 10 years. Previous studies have examined the biocompatibility of Al2O3 and UHMWPE as bulky implant materials. The present study investigated this material as a Blood-contacting material using a standard assessment in vitro and in vivo analysis. The examined items were systemic toxicity, sensitization (guinea pig maximization test), cytotoxicity (elution test), mutagenicity (Ames test), direct contact hemolysis, and thrombogenicity. The studies were performed according to the United States Pharmacopoeia and published previous studies. The samples of both Al2O3 and UHMWPE demonstrated no differences from the negative controls in all tests. These findings indicate that both Al2O3 and UHMWPE are biocompatible materials for double-pivot bearings in the Centrifugal Blood Pump. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 381–386, 1997.

  • Flow visualization evaluation of secondary flow in a Centrifugal Blood Pump.
    ASAIO journal (American Society for Artificial Internal Organs : 1992), 1993
    Co-Authors: Ichiro Sakuma, Kenzo Makinouchi, Setsuo Takatani, Yasuhiro Fukui, Yasuhisa Ohara, Yukihiko Nosé
    Abstract:

    To design a less hemolytic and more antithrombogenic Centrifugal Blood Pump, secondary flow, i.e., vortex and turbulent flow, must be properly controlled. An irregular stream pattern is a cause of hemolysis, and good wash-out around the shaft minimizes thrombus formation. In this study, flow visualization methods were applied to evaluate secondary flow in a Centrifugal Blood Pump. Correlation with results of in vitro hemolysis tests was investigated. Separation of the stream lines from the vanes and patterns implying the existence of vortices were observed in the impeller that showed high hemolysis. By adjustment of vane angles, these irregular patterns could be minimized, and hemolysis decreased as well. Using a similar technique, the flow pattern at the back of the impeller could be visualized, which enabled further investigation of the effects of secondary flow on thrombus formation. This flow visualization was effective in examining secondary flow patterns.

Setsuo Takatani - One of the best experts on this subject based on the ideXlab platform.

  • a cost effective extracorporeal magnetically levitated Centrifugal Blood Pump employing a disposable magnet free impeller
    Proceedings of the Institution of Mechanical Engineers Part H: Journal of Engineering in Medicine, 2011
    Co-Authors: Wataru Hijikata, Tadahiko Shinshi, Taichi Mamiya, Setsuo Takatani
    Abstract:

    In the field of rotary Blood Pumps, contactless support of the impeller by a magnetic bearing has been identified as a promising method to reduce Blood damage and enhance durability. The authors developed a two-degrees-of-freedom radial controlled magnetic bearing system without a permanent magnet in the impeller in order that a low-cost disposable Pump-head for an extracorporeal Centrifugal Blood Pump could be manufactured more easily. Stable levitation and contactless rotation of the ‘magnet-free’ impeller were realized for a prototype Blood-Pump that made use of this magnetic bearing. The run-out of the impeller position at between 1000 r/min and 3000 r/min was less than 40 µm in the radial-controlled directions. The total power consumption of the magnetic bearing was less than 1 W at the same rotational speeds. When the Pump was operated, a flow rate of 5 l/min against a head pressure of 78.66 kPa was achieved at a rotational speed of 4000 r/min, which is sufficient for extracorporeal circulation supp...

  • development of a compact maglev Centrifugal Blood Pump enclosed in a titanium housing
    Journal of Advanced Mechanical Design Systems and Manufacturing, 2008
    Co-Authors: Chi Nan Pai, Jun Ichi Asama, Tadahiko Shinshi, Setsuo Takatani, Akira Shimokohbe
    Abstract:

    A compact Centrifugal Blood Pump consisting of a controlled two-degrees-of-freedom radial magnetic bearing and a brushless DC motor enclosed in a titanium housing has been developed for use as an implantable ventricular assist device. The magnetic bearing also supports axial and angular motions of the impeller via a magnetic coupling. The top housing is made of pure titanium, while the impeller and the stator are coated with pure titanium and Ti-6Al-7Nb, respectively, to improve the biocompatibility of the Pump. The combination of pure titanium and titanium alloy was chosen because of the sensitivity of eddy current type displacement sensors through the intervening conducting wall. The dimensions of the Pump are 69.0 mm in diameter and 28.5 mm in height. During a Pump performance test, axial shifting of the impeller due to hydraulic forces led to variations in the rotational positioning signal, causing loss of control of the rotational speed. This problem was solved by conditioning the rotational positioning signal. With a flow rate of 5 l/min against a head pressure of 100 mmHg, the power consumption and efficiency of the Pump were 5.5 W and 20%, respectively. Furthermore, the hemolysis of the Blood Pump was 43.6% lower when compared to that of a commercially available Pump.

  • Computational fluid dynamics analysis of the pediatric tiny Centrifugal Blood Pump (TinyPump).
    Artificial Organs, 2006
    Co-Authors: K Kido, Jun Ichi Asama, Hideo Hoshi, Katsuhiro Ohuchi, Tadahiko Shinshi, Nobuo Watanabe, H Kataoka, Masaharu Yoshikawa, Setsuo Takatani
    Abstract:

    :  We have developed a tiny rotary Centrifugal Blood Pump for the purpose of supporting circulation of children and infants. The Pump is designed to provide a flow of 0.1–4.0 L/min against a head pressure of 50–120 mm Hg. The diameter of the impeller is 30 mm with six straight vanes. The impeller is supported by a hydrodynamic bearing at its center and rotated with a radial coupled magnetic driver. The bearing that supports rotation of the impeller of the tiny Centrifugal Blood Pump is very critical to achieve durability, and clot-free and antihemolytic performance. In this study, computational fluid dynamics (CFD) analysis was performed to quantify the secondary flow through the hydrodynamic bearing at the center of the impeller and investigated the effects of bearing clearance on shear stress to optimize hemolytic performance of the Pump. Two types of bearing clearance (0.1 and 0.2 mm) were studied. The wall shear stress of the 0.1-mm bearing clearance was lower than that of 0.2-mm bearing clearance at 2 L/min and 3000 rpm. This was because the axial component of the shear rate significantly decreased due to the narrower clearance even though the circumferential component of the shear rate increased. Hemolysis tests showed that the normalized index of hemolysis was reduced to 0.0076 g/100 L when the bearing clearance was reduced to 0.1 mm. It was found that the CFD prediction supported the experimental trend. The CFD is a useful tool for optimization of the hydrodynamic bearing design of the Centrifugal rotary Blood Pump to optimize the performance of the Pump in terms of mechanical effect on Blood cell elements, durability of the bearing, and antithrombogenic performance.

  • Quantification of the secondary flow in a radial coupled Centrifugal Blood Pump based on particle tracking velocimetry.
    Artificial organs, 2005
    Co-Authors: Nobuo Watanabe, H Kataoka, Masuda T, Tomoya Iida, Tetsuo Fujimoto, Setsuo Takatani
    Abstract:

    Secondary flow in the Centrifugal Blood Pump helps to enhance the washout effect and to minimize thrombus formation. On the other hand, it has an adverse effect on Pump efficiency. Excessive secondary flow may induce hemolytic effects. Understanding the secondary flow is thus important to the design of a compact, efficient, biocompatible Blood Pump. This study examined the secondary flow in a radial coupled Centrifugal Blood Pump based on a simple particle tracking velocimetry (PTV) technique. A radial magnetically coupled Centrifugal Blood Pump has a bell-shaped narrow clearance between the impeller inner radius and the Pump casing. In order to vary the flow levels through the clearance area, clearance widths of 0.25 mm and 0.50 mm and impeller washout holes with diameters of 0 mm, 2.5 mm, and 4 mm were prepared. A high-speed video camera (2000 frames per second) was used to capture the particle images from which radial flow components were derived. The flow in the space behind the impeller was assumed to be laminar and Couette type. The larger the inner clearance or diameter of washout hole, the greater was the secondary flow rate. Without washout holes, the flow behind the impeller resulted in convection. The radial flow through the washout holes of the impeller was conserved in the radial as well as in the axial direction behind the impeller. The increase in the secondary flow reduced the net Pump efficiency. Simple PTV was successful in quantifying the flow in the space behind the impeller. The results verified the hypothesis that the flow behind the impeller was theoretically Couette along the circumferential direction. The convection flow observed behind the impeller agreed with the reports of other researchers. Simple PTV was effective in understanding the fluid dynamics to help improve the compact, efficient, and biocompatible Centrifugal Blood Pump for safe clinical applications.

  • control of Centrifugal Blood Pump based on the motor current
    Artificial Organs, 1997
    Co-Authors: Tatsuhiko Iijima, Taro Inamoto, Masamichi Nogawa, Setsuo Takatani
    Abstract:

    : In this study, Centrifugal Pump performance was examined in a mock circulatory loop to derive an automatic Pump rotational speed (rpm) control method. The pivot bearing supported sealless Centrifugal Pump was placed in the left ventricular apex to aorta bypass mode. The pneumatic pulsatile ventricle was used to simulate the natural ventricle. To simulate the suction effect in the ventricle, a collapsible rubber tube was placed in the inflow port of the Centrifugal Pump in series with the apex of the simulated ventricle. Experimentally, the Centrifugal Pump speed (rpm) was gradually increased to simulate the suction effect. The Pump flow through the Centrifugal Pump measured by an electromagnetic flowmeter, the aortic pressure, and the motor current were continuously digitized at 100 Hz and stored in a personal computer. The analysis of the cross-spectral density between the Pump flow and motor current waveforms revealed that 2 waveforms were highly correlated at the frequency range between 0 and 4 Hz, with the coherence and phase angles being close to 1.0 and 0 degrees, respectively. The fast Fourier transform analysis of the motor current indicated that the second harmonic component of the motor current power density increased with the occurrence of the suction effect in the circuit. The ratio of the fundamental to the second harmonic component decreased less than 1.3 as the scction effect developed in the circuit. It is possible to detect and prevent the suction effect of the Centrifugal Blood Pump in the natural ventricle through analysis of the motor current waveform.

Balazs Asztalos - One of the best experts on this subject based on the ideXlab platform.

  • flow visualization measurement for shear velocity distribution in the impeller casing gap of a Centrifugal Blood Pump
    Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing, 1999
    Co-Authors: Takashi Yamane, Masahiro Nishida, Balazs Asztalos, Helen Clarke, Toshio Kobayashi
    Abstract:

    A flow visualization study of a Centrifugal Blood Pump was conducted to find the shear and velocity profiles in the back gap between the impeller and the casing. For a wide range of Reynolds numbers and specific speeds, it was found that high shear exists only in the boundary layers of the moving and stationary walls. The velocity profile was essentially laminar. It was also found that the total thickness of the high shear regions is 0.3-0.6mm for conditions of artificial heart and the thickness is determined only by Reynolds number. Hence, it can be concluded that reducing the impeller velocity is the only way to reduce wall shear stress and that increasing the gap width is not effective.

  • development of design methods for a Centrifugal Blood Pump with a fluid dynamic approach results in hemolysis tests
    Artificial Organs, 1999
    Co-Authors: Toru Masuzawa, H. Takano, Eisuke Tatsumi, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Masahiro Nishida, Seiko Endo, Balazs Asztalos, Yuki Miyazoe
    Abstract:

    : The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for Centrifugal Blood Pumps with lower levels of hemolysis. The Nikkiso Centrifugal Blood Pump was used as a standard model, and Pumps with different values of 3 geometrical parameters were tested. The studied parameters were the radial gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow radial gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected Blood trauma in so far as the Nikkiso Centrifugal Blood Pump was concerned. The radial gap should be considered as a design parameter of a Centrifugal Blood Pump to reduce Blood trauma.

  • computational fluid dynamics analysis to establish the design process of a Centrifugal Blood Pump second report
    Artificial Organs, 1999
    Co-Authors: Yuki Miyazoe, Toru Masuzawa, Tomonori Tsukiya, Takashi Yamane, Masahiro Nishida, Balazs Asztalos, Yoshiaki Konishi, Kazuyuki Ito, Toshio Sawairi, Seiko Endo
    Abstract:

    To establish an efficient design process for Centrifugal Blood Pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso Centrifugal Blood Pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing Blood Pumps in comparison to flow visualization tests and hemolysis tests.

  • flow visualization study to improve hemocompatibility of a Centrifugal Blood Pump
    Artificial Organs, 1999
    Co-Authors: Masahiro Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki Konishi
    Abstract:

    A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a Centrifugal Blood Pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

  • flow visualization measurement of velocity profiles in the impeller housing gap of a Centrifugal Blood Pump
    Journal of Life Support Engineering, 1998
    Co-Authors: Takashi Yaman, Masahiro Nishida, Balazs Asztalos, Helen Clark, Toshio Kobayashi
    Abstract:

    A flow visualization study of a Centrifugal Blood Pump was conducted to find velocity profiles in the gap between the impeller and the housing. Investigating a wide range of Reynolds numbers and specific speeds, it was found that high shear is found only in the boundary layers of the moving and stationary walls and that the total thickness of the boundary layers is 0. 3-0. 6mm depending the Reynolds number.