Gyro Pump Research Articles

In Vitro Study to Estimate Particle Release From a Centrifugal Blood Pump

Centrifugal pumps have been increasingly used in clinical settings. Like roller pumps, centrifugal pumps can cause debris release due to mechanical stress. The objectives of this study were to evaluate in vitro the particle release from a centrifugal pump, Gyro Pump (Japan Medical Materials Co., Osaka, Japan), which is a pivot-bearing supported pump clinically used in Japan, and to identify the released particles. In the clean room Class 10,000, the pump was operated for 24 h at 4000 rpm and 6 L/min in a mock loop filled with lactated Ringer's solution. After 24 h, the sample fluid and a blank were filtered with a 0.45-microm membrane filter for microscopic counting, followed by observation with a scanning electron microscope and element analysis with an X-ray spectrometer. Microscopic countings were 128 +/- 42 in the test samples (n = 10) of the Gyro Pump and 98 +/- 42 in the blank samples (n = 10) (P = 0.12). The oxygen/carbon atomic ratio of the particles in the test samples was 0.32 +/- 0.06, which was similar to the ratio of the particles in the blank sample (0.34 +/- 0.06). The profiles of elements with an X-ray spectrometer showed that the released particles from the Gyro Pump were not derived from the pump materials. In conclusion, an in vitro test system has been established for estimation of particle release from a centrifugal pump. Based upon the results with the system, the Gyro Pump with a pivot-bearing system has little risk to release debris particles even in a severe condition.

Indirect Flow Rate Estimation of the NEDO PI Gyro Pump for Chronic BVAD Experiments

In totally implantable ventricular assist device systems, measuring flow rate of the pump is necessary to ensure proper operation of the pump in response to the recipient's condition or pump malfunction. To avoid problems associated with the use of flow probes, several methods for estimating flow rate of a rotary blood pump used as a ventricular assist device have been studied. In the present study, we have performed a chronic animal experiment with two NEDO PI gyro pumps as the biventricular assist device for 63 days to evaluate our estimation method by comparing the estimated flow rate with the measured one every 2 days. Up to 15 days after identification of the parameters, our estimations were accurate. Errors increased during postoperation days 20 to 30. Meanwhile, their correlation coefficient r was higher than 0.9 in all the acquired data, and estimated flow rate could simulate the profile of the measured one.

The Possibility of a Veno–Arterial Bypass System Using the Abiomed BVS 5000

Effect of Abiomed BVS 5000 (Cardiovascular Inc., Danvers, MA, U.S.A) has been reported for mechanical assist circulation in cardiogenic shock. However, this pump is generally used as a ventricular assist device, not as a device for veno-arterial bypass. Therefore, we evaluated its effectiveness through an experiment. The left anterior descending branch of pigs' heart was ligated to prepare a model of acute myocardial infarction, and after the onset of cardiogenic shock, circulation was initially supported for 30 min using the BVS 5000, followed by support for another 30 min using a Gyro pump (Gyro, Kyocera, Inc., Kyoto, Japan). Subsequently, circulation was additionally supported for 30 min using both a Gyro and an intra-aortic balloon pump (IABP) (Tokai Medical Inc., Aichi, Japan) (Gyro + IABP). Circulation was supported in each group at 30-min intervals in the reversed order of assisted circulation. Although the mean aortic pressure, pump flow, and total flow were not significantly different among the three setups, the pulse pressure was 48.2 +/- 3.3, 12.2 +/- 2.2, and 29.9 +/- 3.8 mm Hg in Abiomed, Gyro, and Gyro + IABP, respectively. Although neither coronary arterial nor myocardial blood flow showed significant differences among the three setups, the renal arterial blood flow was significantly larger in BVS 5000 compared to the other two setups. In this study, we selected an alpha-cube (Platium Cube NCVC 6000, Edwards Research Medical Inc., Salt Lake City, UT, U.S.A.), which is considered as an oxygenator that produces minimum pressure loss. Therefore, the pulsatile flow we obtained with the Abiomed was maintained even after we started using the oxygenator. The pulsatile flow had positive effects on renal circulation and peripheral circulation.

ENDURANCE PERFORMANCE OF GYRO CENTRIFUGAL BLOOD PUMP

Purpose: Our group is developing a double-pivot bearing centrifugal pump for long-term ventricular assistance. Previous studies have estimated bearing life at 5 years for LVAD and 8 years for RVAD. Endurance testing for 1-year demonstrated that top female bearing wear was 3 times greater for LVAD than RVAD. Top bearing is critical because pump impeller is maintained at top contact position during operation. To improve bearing life, the top female bearing radius was increased, and magnet coupling force was increased. We report endurance test results of modified double-pivot bearing centrifugal pump. Methods: Eight Gyro pumps are being operated in LVAD mode. Test stations consist of mock ventricle, arterial compliance, arterial resistor, and atrial chamber. Pumps are operated at 5 L/min at peak outflow pressure of 100 mmHg. Mock ventricles are operated at 78 beats/min with stoke volume of ∼30 ml/beat. Pump fluid is normal saline at 37oC. Results: As of January 14, 2005, pumps have accumulated test periods of 331(n=4), 322 (n=1), 313 (n=1), 212 (n=1), and 73 days (n=1). Measured pump flows are 5.03 + 0.06 L/min at mean outflow pressure of 93 + 3 mmHg and mean filling pressure of 26 + 5 mmHg. Pump speed averaged 1810 + 50 RPM with power consumption of 0.29 + 0.03 amps and a system efficiency of 19.2 + 1.7%. There have been no pump/actuator malfunctions without noticeable vibration or noise. Conclusion: Eight centrifugal pumps have 6.1 cumulative years of in vitro testing without failure. Studies will be continued for another year to validate 2-year endurance of double-pivot bearing Gyro centrifugal blood pump.

Current status of the gyro centrifugal blood pump--development of the permanently implantable centrifugal blood pump as a biventricular assist device (NEDO project).

The New Energy and Industrial Technology Development Organization (NEDO) project was started in 1995. The goal is the development of a multipurpose, totally implantable biventricular assist device (BVAD) that can be used for any patient who suffers from severe heart failure. Our C1E3 (two-week pump) centrifugal pump, called the Gyro pump, has three design characteristics: a magnetic coupling and double pivot bearing system, an eccentric inlet port, and secondary vanes on the bottom of the impeller. The pump was miniaturized. The C1E3 evolved into the NEDO PI-601, a totally implantable centrifugal pump for BVAD. The current NEDO PI-710 pump (five-year pump) system includes a centrifugal pump with pivot bearings, a hydraulically-levitated impeller, an rpm-controlled miniaturized actuator (all-in-one actuator plus controller), an emergency clamp on the left outflow, and a Frank-Starling-type flow control. The final mass production model is now finalized, and the final animal study and two-year endurance studies are ongoing.

HYDRAULIC SUSPENSION GYRO PUMP

An impeller suspension mechanism is a major concern to avoid thrombus formation for long-term centrifugal pump application. A gyro-type centrifugal pump has been developed as permanent implantable ventricular assist device (VAD). Currently, this titanium-made gyro pump utilizes a novel hydraulic impeller suspension system. This study aims to evaluate the anti-thrombogenicity of the hydraulic suspension (HS) gyro pump. In vitro studies were conducted to examine the platelet adhesion at the bottom pivot, which is a primary lesion of white thrombus after pump implantation. For the pump hemorheology analysis, the particle tracing flow visualization was performed utilizing. In addition to these in vitro studies, current in-vivo animal studies were retrospectively examined.TableHS pumps demonstrated 50% lower platelet adhesion rate at the bottom pivot lesion compared to the control gyro pump. With the flow visualization study, continuous washout flow was created around the the center pivot behind the impeller. Total 20 pumps were implanted to 10 calves, and no thromboembolism was observed. Only one case had thrombus formation inside the right pump head due to low pump flow caused by the outflow graft kinking. This HS gyro pump is a compact, secure, and affordable VAD.

Left ventricular support using the Gyro C1E3 centrifugal pump: durability of the double-pivot, blood-immersed bearing in prolonged clinical use

The Gyro Pump C1E3 has a double-pivot bearing system to support its impeller in this completely seal-less centrifugal pump. Previous experimental studies have suggested long-term durability of this bearing system; however, there have been no data on prolonged clinical use. We present a patient with cardiogenic shock caused by ventricular septal perforation who was supported by a Gyro C1E3 for 19 days for extracorporeal left ventricular support. The morphological changes in the pump's bearings were assessed. Over the 19 days, the C1E3 showed stable pumping and no mechanical trouble. Measurement of female pivot depth revealed that the deformity of the bottom female pivot is greater than that of the top female pivot. These results suggest that morphological change in the bottom female pivot may result from spinning of the impeller in the bottom contact phase during a prolonged period of left ventricular support.

Morphological inspection of 80 consecutive Gyro pumps after cardiopulmonary bypass

We have been using the Gyro centrifugal pump C1E3 for cardiopulmonary bypass in anticipation of high efficiency, low hemolysis, and antithrombogenicity of this pump. However, the clinical evaluation of this pump remains to be clarified, because it has been a short time since the pump appeared in clinical situations. The aim of the present study is to inspect and analyze the Gyro pumps morphologically after clinical use. We examined 80 consecutive pumps after cardiopulmonary bypass for 186 ± 67 min with a mean flow rate of 2.52 ± 0.22 l/min/m2 at a mean rotational speed of 2485 ± 81.1 rpm. Although no abnormal findings were present in 79 pumps, one pump was found to contain effusion at the connection between the impeller body and the shaft. The extudate was supposed to be blood, based upon the results of X-ray spectrometer analysis. The cause was determined to be the upward deviation of the shaft off the impeller body. Scanning electron microscopy showed scratches on a part of the bottom housing and a smooth surface of both the male and female pivots of the pump. Surface profile measurement revealed that the deformity of the female pivots was 0.14 mm (top) and 0.05 mm (bottom). These observations suggest that the floating force and vibration by the rotating impeller acted on the joint zone between the alumina ceramic shaft and the polycarbonate impeller body, resulting in dissection of the adhesive agent from the polycarbonate. Although this abnormality may be rare, the structural design still may need to be improved.

Morphological changes of the pivot bearings in the Gyro Pump C1E3 after clinical use

The Gyro Pump C1E3 incorporates a doublepivot bearing system as a completely sealless centrifugal pump. The male pivot is made of alumina ceramic, and the female is made of polyethylene. Therefore, the durability of this pump depends upon morphological changes of the female polyethylene pivots, which we examined after clinical usage in the present study. We examined 30 pumps, which were used for cardiopulmonary bypass (CPB), in terms of weight, depth, and surface roughness of the female polyethylene pivots. To determine changes caused by clinical use, we also examined 10 pumps of the same lot numbers with the pumps clinically used and stocked in the factory. There were no significant changes in weight of top and bottom pivots. Also, there was no significant difference in depth and surface roughness of the top pivots. However, there was a significant increase in depth and a decrease in surface roughness of the bottom pivots from clinical use. The results revealed that the bottom pivot, rather than the top pivot, is subject to mechanical deformation by clinical use of the Gyro Pump for CPB. Since morphological changes of the bottom pivot may result from spinning of the impeller at the bottom contact phase, the magnetic coupling distance may need to be increased to obtain more stable spinning of the impeller in a routine CPB.

Gyro pump wear and deformation analysis in vivo study: creep deformation.

The Gyro pump has a double pivot bearing system to support its impeller. In this study, the integrity of the bearing system was examined after ex vivo studies. The pumps were implanted into calves and evaluated for different periods as a paracorporeal left ventricular assist device (LVAD). One pump was subjected to a test of 30 days, 1 for 15 days, 4 for 14 days, 1 for 10 days, 1 for 7 days, 2 for 4 days, and 4 for 2 days. One additional pump was subjected to percutaneous cardiopulmonary support (PCPS) condition for 6 days (total pressure head 500 mm Hg with a pump flow rate of 3 L/min). The anticoagulation treatment consisted of a continuous administration of heparin to maintain an achieved clotting time (ACT) of 200-250 s during the LVAD study and 250-300 s during the PCPS study. After the experiment, the pumps were disassembled, and the wear and deformation of male and female bearings were analyzed. There were no dimensional changes on male bearings but there were on female bearings. Wear and deformation of the female bearings were calculated as follows: wear and deformation = (depth of female before pumping) - (depth after pumping). Thirteen assembled Gyro pumps were disassembled to measure the depth of the female bearings before pumping. There was no statistical relationship between the wear and deformation and the motor speed x driving period. From these results, the deformation was not due to wear but to the creep or elastic deformation. This study suggested that the double pivot bearing system of the Gyro pump is highly durable.

Development of the NEDO implantable ventricular assist device with Gyro centrifugal pump.

The Gyro centrifugal pump, PI (permanently implantable) series, is being developed as a totally implantable artificial heart. Our final goal is to establish a "functional TAH," a totally implantable biventricular assist system (BiVAS) with centrifugal pumps. A plastic prototype pump, Gyro PI 601, was evaluated through in vitro and in vivo studies as a single ventricular assist device (VAD). Based upon these results, the pump head material was converted to a titanium alloy, and the actuator was modified. These titanium Gyro pumps, PI 700 series, also were subjected to in vitro and in vivo studies. The Gyro PI 601 and PI 700 series have the same inner dimensions and characteristics, such as the eccentric inlet port, double pivot bearing system, secondary vane, and magnet coupling system; however, the material of the PI 700 is different from the PI 601. The Gyro PI series is driven by the Vienna DC brushless motor actuator. The inlet cannula of the right ventricular assist system (RVAS) specially made for this system consists of 2 parts: a hat-shaped silicone tip biolized with gelatin and an angled wire reinforced tube made of polyvinylchloride. The pump-actuator package was implanted into 8 calves in the preperitoneal space, bypassing from the left ventricle apex to the descending aorta for the left ventricular assist system (LVAS) and bypassing the right ventricle to the main pulmonary artery for the RVAS. According to the PI 601 feasibility protocol, 2 LVAS cases were terminated after 2 weeks, and 1 LVAS case and 1 RVAS were terminated after 1 month. The PI 700 series was implanted into 4 cases: 3 LVAS cases survived for a long term, 2 of them over 200 days (72-283 days), and 1 RVAS case survived for 1 month and was terminated according to the protocol for a short-term antithrombogenic screening and system feasibility study. Regarding power consumption, the plastic pump cases demonstrated from 6.2 to 12.1 W as LVAS and 7.3 W as RVAS, the titanium pump cases showed from 10.4 to 14.2 W as LVAS and 15.8 W as RVAS. All cases exhibited low hemolysis. The renal function and the liver function were maintained normally in all cases throughout these experimental periods. In the 2 RVAS cases, pulmonary function was normally maintained. No calves demonstrated thromboembolic signs or symptoms throughout the experiments except Case 1 with the plastic pump. However, in the plastic pump cases, bilateral renal infarction was suspected in 2 cases during necropsy whereas no abnormal findings were revealed in the titanium pump cases. There were also no blood clots inside the PI 700 series. As for the 601, the explanted pumps demonstrated slight thrombus formations at the top and bottom pivots except in 1 case. The Gyro PI series, especially the PI 700 series, demonstrated superior performance, biocompatibility, antithrombogenicity and low hemolysis. Also, the durability of the actuator was demonstrated. Based on these results, this titanium centrifugal pump is suitable as an implantable LVAS and RVAS. It is likely that the Gyro PI series is a feasible component of the BiVAS functional TAH.

DEVELOPMENT OF A MINIATURIZED IMPLANTABLE CENTRIFUGAL BLOOD PUMP-BAYLOR GYRO KP PUMP-

Currently, commercialized implantable blood pumps have a large mass volume and restricted their application to patients with 1.5 m2 body surface area or above. Pump miniaturization is essential for implantation in pediatric and small sized patients. The Baylor KP centrifugal pump is being developed for smaller patients as well as adult patients. The outer size of the KP pump is 4.6 ± 2.8 cm (diameter x height) and impeller diameter is 35 mm. The basic design of the KP pump (double pivot bearing, eccentric inlet, secondary impeller vanes, magnetic coupling drive) were inherited from Gyro pumps, which have demonstrated less thrombogenicity and less blood trauma in previous long-term studies. The pump is driven by University of Vienna implantable actuator, which is newly fabricated for this KP pump. The pump system attains left ventricular assist condition (5L/min against 100 mm Hg) at 3000 RPM and the required power is around 6 W. A 2-week ex-vivo calf study was performed using this pump system. The mean pump flow and rotational speed throughout the experiment was 3.4 L/min and 3500 RPM, respectively. The mean power consumption was 7.8 W. No thromboembolic signs were observed in this animal. The pump and actuator were then implanted inside a calf. A mean pump flow of 5.4 L/min was obtained at only 2400 RPM and 4.2 W. No actuator failure occurred in these experiments. The KP pump system is considered to be feasible as an implantable LVAS.

CFD STUDIES OF C1E3 GYRO CENTRIFUGAL BLOOD PUMP

A double pivot bearing Gyro pump C1E3 has been developed for cardiopulmonary bypass purposes as well as intermediate and long-term centrifugal ventricular assistance. In long-term ex-vivo animal studies, with an ACT around 200–250 sec, firmly attached fibrin deposit was detected at the bottom shaft after two days of pumping; whereas, no deposit was found at the top shaft of the impeller. However, no signs of thrombembolism were detected in the calves, or clinically, nor macroscopically or histologically. In order to characterize blood flow in the CIE3 pump computational fluid dynamic studies (CFD) were undertaken. CFD proved that there is effective wash out at the top shaft of the impeller as well as the top female bearing. Even though the fluid velocity, which increases to the periphery, was rather low. The CFD further demonstrated secondary blood flow at the bottom side of the impeller generated by secondary vanes leads to an effective blood clearance. Blood velocity was centrally the lowest, increasing peripherally. In vitro testing revealed excellent anti-blood-traumatic features with a Normalized Index of Hemolysis (NIH) of 0.0007 g/1OOL in an LVAD condition. Ex-vivo studies confirmed these data with average free plasma hemoglobin in 5 calves of 4.15 mg/dl +/− 2.7. The CFD studies showed very low shear rates at the impeller corpus with just small areas of high shear stress in the peripheral portion of the top impeller vane. High shear stress was demonstrated at the introduction of the outlet port, where the blood velocity is the highest. Conclusion: CFD studies confirm the high anti-traumatic features with low shear rates in the housing and impeller. Furthermore, blood wash out from the impeller bottom with low flow centrally as well as at the top and bottom male bearing occurs. These areas have to be further investigated to eliminate any deposition of fibrin.

Clinical evaluation of the Gyro Pump C1E3 as a cardiopulmonary bypass pump.

The Gyro Pump C1E3 is a new centrifugal pump with numerous features, including a ceramic pivot bearing system, secondary vanes, and an eccentric inlet port. To evaluate its biocompatibility, antithrombogenicity, and produced hemolysis, we used the Gyro Pump during cardiopulmonary bypass (CPB) for coronary artery bypass grafting (CABG) cases to compare it with the BioMedicus pump. From September 1998 to February 1999, 30 consecutive patients underwent CABG under conventional CPB. Fifteen patients were supported by the Gyro Pump C1E3 (Group G), and the remaining 15 patients, by a BioMedicus BP-80 pump (Group B). In both groups, flow rate was equivalent. Blood samples were taken as follows: preoperative, 60 minutes after the end of the procedure, and at postoperative days (POD) 0, 1, and 2. We evaluated the plasma free hemoglobin (free Hb) as an indication of hemolysis; beta-thromboglobulin (beta-TG) and platelet factor four (PF-4) as an indication of platelet deterioration; C3, C4, CH50 for complement activation; coagulation parameters, fibrinolytic factor, thrombomodulin, nitric oxide (NO), and endothelin as an indication of endothelial deterioration. This was the first clinical sized Gyro Pump CIE3. De-airing from the pump was easily accomplished via the eccentric oblique inlet port. The system, including its console, was easily and simply controlled. Perioperative laboratory data were not markedly changed in either group with demonstrated equivalence for biocompatibility and hemolysis. After pumping, no thrombus formation or pivot wear were observed inside the pump. This atraumatic, small centrifugal pump appears well suited not only for CPB but also for circulatory support.

Feasibility of a tiny Gyro centrifugal pump as an implantable ventricular assist device.

The Gyro pumps were developed for long-term circulatory support. The first generation Gyro pump (C1E3) achieved 1 month paracorporeal circulatory support in chronic animal experiments; the second generation (PI702) implantable ventricular assist device (VAD) was successful for over 6 months. The objective of the next generation Gyro pump is for use as a long-term totally implantable VAD and for pediatric circulatory support. This tiny Gyro pump (KP101) was fabricated with the same design concept as the other Gyro pumps. The possibility of an implantable VAD was determined after performance and hemolysis test results were compared to those of the other Gyro pumps. The pump housing and impeller were fabricated from polycarbonate with an impeller diameter of 35 mm. The diameter and height of the pump housings are 52.3 mm and 29.9 mm, respectively. At this time, a DC brushless motor drives the KP101, which is the same as that for the C1E3. The pump performance was measured in 37% glycerin water at 37 degrees C. Hemolysis tests were performed utilizing a compact mock loop filled with fresh bovine blood in a left ventricular assist device (LVAD) condition at 37 degrees C. The KP101 achieved the LVAD conditions of 5 L/min and 100 mm Hg at 2,900 rpm; generated 10 L/min against 100 mm Hg at 3,200 rpm; 3 L/min against 90 mm Hg at 2,600 rpm; and 2 L/min against 80 mm Hg at 2,400 rpm. In addition, the pump efficiency during this experiment was 12.5%. The other Gyro pumps. that is, the C1E3, PI601, and PI701, in an LVAD condition require 1,600, 2,000, and 2,000 rpm, respectively. The KP101 produced a normalized index of hemolysis (NIH) value of 0.005 g/100 L. With regard to the NIH, the other Gyro pumps, namely the C1E3, PI601, and PI701 demonstrated 0.0007, 0.0028, and 0.004 g/100 L, respectively. The KP101 produced an acceptable pressure flow curve for a VAD. The NIH value was higher than that of other Gyro pumps, but is in an acceptable range.

Development of a totally implantable biventricular bypass centrifugal blood pump system

Background. During the past 2 years, the development of a totally implantable biventricular bypass rotary blood pump system has been made. Methods. An extracorporeal gyro centrifugal pump, the CIE3, was miniaturized and developed into the PI601, a totally implantable plastic pump. Two-day anatomic and hemodynamic feasibility studies demonstrated that these two pump systems were easily implantable inside a calf’s abdominal wall, directly under the diaphragm. The priming volume of the pump was 20 mL, with sufficient cardiac outputs at approximately 2,000 rpm and requiring less than 10 W of power. Two-week antithrombogenic screening tests also revealed these pump systems to be quite antithrombogenic. In addition, 1-month system reliability studies demonstrated fail-safe reliable performances. Results and Conclusions. Encouraged by these preliminary studies, the PI601 model was converted to the permanently implantable titanium gyro pump PI702 model. The long-term implantations were initiated approximately 3 months ago, and two such long-term LVAD studies are currently underway with no sign of difficulty (October 10, 1997). They were followed 283 days and 72 days, respectively. Both terminated due to functional inflow obstruction. There were no blood clots or emboli at autopsy.

Protein adsorption onto ceramic surfaces.

Ceramics seldom have been used as blood-contacting materials. However, alumina ceramic (Al2O3) and polyethylene are incorporated into the pivot bearings of the Gyro centrifugal blood pump. This material combination was chosen based on the high durability of the materials. Due to the stagnant flow that often occurs in a continuous flow condition inside a centrifugal pump, pivot bearing system is extremely critical. To evaluate the thombogenicity of pivot bearings in the Gyro pump, this study sought to investigate protein adsorption, particularly albumin, IgG, fibrinogen, and fibronectin onto ceramic surfaces. Al2O3 and silicon carbide ceramic (SiC) were compared with polyethylene (PE) and polyvinylchloride (PVC). Bicinchoninic acid (BCA) protein assay revealed that the amount of adsorbed proteins onto Al2O3 and SiC was significantly less than that on PVC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that numerous proteins adsorbed onto PVC compared to PE, Al2O3, and SiC. Identification of adsorbed proteins by Western immunoblotting revealed that the adsorption of albumin was similar on all four materials tested. Western immunoblotting also indicated lesser amounts of IgG, fibrinogen, and fibronectin on Al2O3 and SiC than on PE and PVC. In conclusion, ceramics (Al2O3 and SiC) are expected to be thromboresistant from the viewpoint of protein adsorption.

Quantitative approach to control spinning stability of the impeller in the pivot bearing-supported centrifugal pump.

The Gyro C1E3 pump has been developed as a completely sealless centrifugal pump driven by a magnetic coupling system for long-term usage. The Gyro C1E3 pump is a pivot bearing-supported pump in which the impeller is supported with the top and bottom pivot bearings. In the Gyro C1E3 pump, the impeller spinning is affected by the force balance between the floating force (Ff[N]) of the hydrodynamic effect and the magnetic thrust force (Tf[N]). The authors quantitatively investigated the floating force of the impeller in vitro to determine the magnetic coupling distance (MCD[mm]) that would result in stable impeller spinning. In vitro tests were performed using a loop filled with 37% glycerin solution to obtain the relationship between the MCD and floating speed (Rf, rotational speed when the impeller starts floating [rpm]) and the relationship between the MCD and Tf. From the obtained relationships, we calculated Ff and determined the relationship between the Ff and the rotational speed (R). Furthermore, we determined the relationship between d (minimum required MCD [mm]) and R from the results of determining the relationship of the MCD and Tf and of the Ff and R. The following relationships were obtained: Rf = 6.24 x 10(4) x MCD-1.35; Tf = 5.27 x 10(3) x MCD-2.29; Ff = 4.71 x 10(-6) x RPM1.69; and d = 9.02 x RPM-0.85 where RPM is the rotational speed. It was demonstrated that the floating force of the impeller is a function only of the rotational speed in the pivot bearing-supported Gyro C1E3 pump. The floating force is estimated to be 10 N to 40 N at rotational speeds of 1,500 rpm to 3,000 rpm at which the Gyro pump may be used in most clinical situations. It would be possible to control the impeller position of the Gyro pump automatically at the stable spinning condition by controlling the adequate magnetic coupling distance based upon its relationship with the rotational speed which was obtained in this study.

Preclinical evaluation of the Kyocera Gyro centrifugal blood pump for cardiopulmonary bypass.

The Kyocera Gyro pump has been developed as a completely seal-less centrifugal pump to overcome the problems of the conventional centrifugal pumps. The Gyro pump is a double pivot bearing-supported centrifugal pump with several specific design features, including its eccentric inlet port. We investigated the feasibility of the Gyro pump for cardiopulmonary bypass (CPB) in a bovine model, comparing it with the BioMedicus pump (BP-80). Ten healthy calves (5: Gyro pump, 5: BP-80) underwent 6 h of mildly hypothermic CPB at approximately 33 degrees C. Both pumps provided more than 50 ml/kg/min without any incidents. The haemodynamics of both groups remained stable within the normal range. All haematology and biochemistry data demonstrated no significant differences between the two groups. However, values of plasma-free haemoglobin and lactate dehydrogenase were less throughout the experiments of the Gyro pump than those of the BP-80. To obtain flow equivalent to that of the BP-80, the Gyro pump needed less rotational speeds than the BP-80 (2749.7 +/- 233.3 versus 3170.6 +/- 300.8 rpm. p < 0.05). Less rotational speed in addition to the difference in operating principle may contribute to less blood damage during the CPB OF the Gyro pump. After pumping for CPB, no leakage or thrombus formation was observed in either pump. The present study indicated that the Kyocera Gyro pump can be applied as a centrifugal pump for CPB with the same performance as the BP-80 and with relatively less haemolysis than the BP-80.

Hemolytic effect of the secondary vane incorporated into the back side of the impeller.

The hemolytic effect of the secondary vane system, the antithrombogenic structure incorporated into the back side of the impeller of the C1E3 Gyro pump, was investigated. Impellers with 0, 2, 3, and 4 secondary vanes and an additional impeller with 2 secondary channels were fabricated and incorporated into the C1E3 pump casings. Hemolysis tests were performed under cardiopulmonary bypass conditions (flow rate 4.5 L/min, total pressure head 350 mm Hg) using flesh bovine blood. The normalized indices of hemolysis (NIH) of the pumps with 0, 2, 3, and 4 secondary vanes and the pump with 2 secondary channels were 0.0797, 0.0866, 0.104, 0.157, and 0.0591, respectively. These results indicated that design of the impeller with 2 secondary channels, which was the original design of C1E3 Gyro pump, was less hemolytic than the design with secondary vanes. Additionally, the possibility of the secondary channel system for the impeller bottom was demonstrated favorably.