Cora valveless pulsatile rotary pump: new design and control

For decades, research for developing a totally implantable artificial ventricle has been carried on. For 4 to 5 years, two devices have been investigated clinically. For many years, we have studied a rotary (but not centrifugal) pump that furnishes pulsatile flow without a valve and does not need external venting or a compliance chamber. It is a hypocycloidal pump based on the principle of the Maillard-Wankel rotary compressor. Currently made of titanium, it is activated by an electrical brushless direct-current motor. The motor-pump unit is totally sealed and implantable, without noise or vibration. This pump was implanted as a left ventricular assist device in calves. The midterm experiments showed good hemodynamic function. The hemolysis was low, but serious problems were encountered: blood components collecting on the gear mechanism inside the rotor jammed the pump. We therefore redesigned the pump to seal the gear mechanism. We used a double system to seal the open end of the rotor cavity with components polished to superfine optical quality. In addition, we developed a control system based on the study of the predicted shape of the motor current. The new design is now underway. We hope to start chronic experiments again in a few months. If the problem of sealing the bearing could be solved, the Cora ventricle could be used as permanent totally implantable left ventricular assist device.     

Progress in the development of a transcutaneously powered axial flow blood pump ventricular assist system

Development of the Jarvik 2000 intraventricular assist system for long-term support is ongoing. The system integrates the Jarvik 2000 axial flow blood pump with a microprocessor based automatic motor controller to provide response to physiologic demands. Nine devices have been evaluated in vivo (six completed, three ongoing) with durations in excess of 26 weeks. Instrumented experiments include implanted transit-time ultrasonic flow probes and dual micromanometer LV/AoP catheters. Treadmill exercise and heart pacing studies are performed to evaluate control system response to increased heart rates. Pharmacologically induced cardiac dysfunction studies are performed in awake and anesthetized calves to demonstrate control response to simulated heart failure conditions. No deleterious effects or events were encountered during any physiologic studies. No hematologic, renal, hepatic, or pulmonary complications have been encountered in any study. Plasma free hemoglobin levels of 7.0 +/- 5.1 mg/dl demonstrate no device related hemolysis throughout the duration of all studies. Pathologic analysis at explant showed no evidence of thromboembolic events. All pump surfaces were free of thrombus except for a minimal ring of fibrin, (approximately 1 mm) on the inflow bearing. Future developments for permanent implantation will include implanted physiologic control systems, implanted batteries, and transcutaneous energy and data transmission systems.     

高压泵电机转子轴向窜动故障分析与处理

中板高压除鳞系统高压除鳞泵电机转子发生轴向窜动,造成电机滑动,轴承乌金面磨损严重,致使电机振动增大,温度升高。本文根据高压电机的设计与安装,从电机磁力中心线的位置调整,电机转子扬度以及轴承定位游隙等问题入手,全面阐述并从根本上解决了中板高压除鳞泵电机滑动轴承乌金面磨损及电机异常振动、异响、温升的问题,避免了电机因滑动轴承损坏导致电机扫膛烧坏的可能后果。     

High efficiency magnetic bearing for a rotary blood pump

Mohawk Innovative Technology, Inc. (MiTi; Albany, NY) and the Cleveland Clinic Foundation (Cleveland, OH) have been engaged in a joint project to develop a new, high efficiency magnetic bearing for use in a rotary blood pump. Such a bearing would have some advantages with respect to permitting large, low shear clearances and avoiding crevice-like pivot interfaces and surface wear related issues. While magnetically suspended blood pumps have been demonstrated, other prototypes reported in the literature consume 5-15 W of power to energize the bearing. The MiTi bearing has been prototyped and tested. The design is a hybrid configuration, radially passive and axially active. The rotor-and-bearing system has been run in air and in blood analog solution, in all orientations. Measurements show a bearing power consumption below 0.5 W. Vibration peaked at 0.2 g in blood analog solution; frequency analysis indicated that this was primarily related to motor design features. Measured displacements from the equilibrium position were less than 0.005 cm. Based on this highly successful bearing prototype, an integrated pump/bearing system is now being developed.     

Results of chronic animal experiments with a new version of a magnetically suspended centrifugal pump

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighing 50-70 kg were used in this study. A left heart assist system was established with cannulas into the descending aorta and the left ventricular apex. In two sheep the MSCP was positioned outside the body and in one sheep implanted on the chest wall. The pumping flow was estimated by the motor current and motor speed. The temperature of the pump and the muscle near the pump was recorded for 10 days after operation. The duration of continuous pumping was 60, 140, and 230 days+ (ongoing), respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension in the second sheep. No thrombus or embolus was observed after sacrifice of the second sheep. The third sheep has been going well despite skin necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degrees C immediately after the operation and gradually reduced to 41 degrees C. The MSCP is a reliable pump for long-term circulatory assist.     

Blood flow analysis for the secondary impeller of an IVAS heart pump

The rotodynamic heart pump (IVAS), designed by the Cleveland Clinic Foundation, includes a secondary flow path along the journal bearing, through a secondary impeller, and over the rotor outer surface. The flow behaviors of the blood through the journal bearing and the secondary impeller are investigated by a computational fluid dynamics method that solves the 3-dimensional Navier-Stokes equations using a new solution algorithm. Results of the analyses include: 1) the blood flow patterns within the journal bearing, 2) the effect of the non-uniform bearing clearance on the flow patterns of the impeller cavity, 3) the flow patterns around a secondary impeller blade that include effects of tip clearance and the gap between the blade and the inner or outer side wall, 4) effects of the blade angles on the secondary impeller performance, and 5) the shear stress distribution.     

An implantable centrifugal blood pump for long term circulatory support

A compact centrifugal blood pump was developed as an implantable left ventricular assist system. The impeller diameter is 40 mm and the pump dimensions are 55 x 64 mm. This first prototype was fabricated from titanium alloy, resulting in a pump weight of 400 g including a brushless DC motor. Weight of the second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon to improve blood compatibility. Flow rates of over 7 L/min against 100 mmHg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system ("Cool-Seal") is used as a shaft seal. In this seal system, seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. The purge fluid is continuously purified and sterilized by an ultrafiltration filter incorporated into the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular apex-descending aorta bypass was performed utilizing a PTFE (Polytetrafluoroethylene) vascular graft, with the pump placed in the left thoracic cavity. In two in vivo experiments, pump flow rate was maintained at 5-8 L/min, and pump power consumption remained stable at 9-10 W. All plasma free hemoglobin levels were measured at < 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (< 0.5 ml/ day). Both animals remain under observation after 162 and 91 days of continuous pump function.     

湘钢高线大型立式泵橡胶导轴承技术改进设计

从湘钢高线摩根轧机水处理配套的 60 0 L A— 2 3型立式轴流泵叶轮磨损故障的典型剖析 ,论述了叶轮离心力和橡胶轴承磨损量分别对泵运行的影响关系 ,并依据现场实际 ,改进橡胶轴承水润滑的设计参数 ,有效减少磨损 ,确保设备的长周期正常运转     

The pulsatile impeller pump for left ventricular assist

Because of severe hemolysis, especially on producing pulsatile flow by changing the rotating speed of the impellers, the traditional centrifugal pump was rarely used for long-term support of the failing heart. We therefore developed a motor driven pulsatile implantable impeller pump. The pulsatility was achieved by changing the rotating speed via introducing a square waveform voltage into the motor coil. The impeller vane was designed to have both radial and axial curves according to the stream surface and stream lines to reduce the thrombosis and hemolysis. Nine calves weighing 80 to 100 kg were used. With the calves under endotracheal general anesthesia, left posterolateral thoracotomy was performed to connect the inflow tube with the left atrial appendage and to anastomose the outflow tube with the descending aorta. The calves usually awoke and stood up within hours after discontinuation of anesthetics. Within 7 days, continuous monitoring of electrocardiogram, systemic and pulmonary arterial pressures, and central venous pressure were performed to adjust the pump flow to 40% to 50% of the cardiac output. During the survival of 4 to 54 days (mean 16.3 +/- 19.3 days with two calves surviving longer than 1 month), no significant deterioration of liver or renal function was noted. Because of bleeding, hemoglobin reduced from 11.4 +/- 1.8 to 9.0 +/- 1.3 g/dl, and the hematocrit decreased from 34.5 +/- 4.7 to 26.7 +/- 4.6%. No significant changes of free hemoglobin were noted. In our results, the device revealed competent pulsatile function without severe blood damage or organ dysfunction.     

Control of the pressure flow relationship with a magnetically suspended centrifugal pump in a chronic animal experiment

A magnetically suspended centrifugal pump (MSCP) has been developed for long-term ventricular support. Effective torque to blood of the MSCP is exactly proportional to a motor current because of no friction inside the MSCP. The authors have devised new driving modes using these characteristics and applied it to a chronic animal experiment. Three driving modes were compared: 1) a constant rotational speed (N), 2) a constant motor current (I), and 3) a controlled motor current (CI). In two of nine sheep, the MSCPs were operated by the N and in seven by the I mode. The motor current and the rotational speed were always monitored. The CI mode was studied by altering the resistance of the vessels. In the I mode, the rotational speed varied depending upon the pressure head, and the slope of the pressure-flow (P-Q) relationship was steeper than that of the N mode, so that the pump flow was stabilized. In the CI mode, in which the motor current increased to compensate for the decrease in pump flow as the rotational speed increased, the P-Q slope was effectively controlled when the resistance was changed. The MSCP was able to control the P-Q slope without monitor of the pump flow. Various driving modes could be selected according to changes in resistance.     

设备故障诊断技术在水泵中的应用

结合设备故障诊断技术分析方法,针对2^#清水泵在运行过程中振动的劣化趋势,进行故障诊断分析,确定轴承内圈存在问题,并通过更换轴承和叶轮,解决了水泵振动异常问题,使机组恢复正常运行。     

新型摆线转子泵啮合特性的研究

对一种新型圆弧摆线内啮合转子泵进行了研究.新型转子泵在保证连续传动的基础上,将密封与传动的功能赋予齿廓的不同部分,从而避免了内转子的每个齿始终与外转子接触,使得其啮合特性得到极大改善--从根本上消除了普通转子泵所特有的外转子滑动系数出现极大值的现象,并使啮合角的变化范围更加合理.与普通转子泵相比,新型转子泵大大减少了磨损,降低了对转子制造安装精度的要求.因此,新型转子泵可以采用较普通转子泵更高的工作转速、更多的齿数,并获得更大的流量、更小的波动和更小的磨损.分析了新型圆弧摆线内啮合转子泵内外转子齿廓的构成及啮合原理,并与普通摆线转子泵进行了啮合特性对比分析.     

Importance of pre-treatment radiation absorbed dose estimation for radioimmunotherapy of non-Hodgkin''s lymphoma

We have been developing a new type of centrifugal pump for long-term use. The magnetically suspended centrifugal pump (MSCP) contains no shaft and seal so that long life expectancy is predicted. Paracorporeal left ventricular (LV) assist circulation between the left atrium and the descending aorta was instituted using sheep. The flow rates ranged from 2.5-5.5 L/min. The sheep that lived the longest (46 days) died of an embolism as a result of the thrombus in the pump. No thrombus formation was observed in other pumps. Plasma free hemoglobin levels ranged from 9 to 18 mg/dl, which led to the conclusion that the hemolysis level remained within an acceptable range. Two driving modes were compared. The slope of the pressure-flow relationship plot under a constant motor current mode was steeper than that under a constant rotational speed mode, and thus, the flow fluctuation decreased. In conclusion, the MSCP is durable for more than a month at the current stage of development and is a promising device for long-term ventricular assist.     

Ex vivo evaluation of the NASA/DeBakey axial flow ventricular assist device. Results of a 2 week screening test

The authors investigated the antithombogenicity of the NASA/DeBakey axial flow ventricular assist device in an ex vivo calf model. The device is 3 inches in length and 1 inch in largest diameter. The pump weighs 53 g and displaces 15 ml. The unit consists of three major components: a flow straightener, a spinning inducer/impeller, and a diffuser. The impeller has rod shaped permanent magnets embedded within the six blades and is activated magnetically by a motor stator that is positioned outside the flow tube. Previous 2 day screening tests demonstrated an antithrombogenic configuration in short-term implantation. Based on the results of these 2 day screening tests, five pumps with the best configuration were implanted into a calf for 2 weeks for anti thrombogenicity confirmation. Pumps were implanted paracorporeally, and heparin was used to maintain activated clotting time to approximately 250 sec. Each pump was changed every 2 weeks as planned. During the experiment, all pumps demonstrated stable pumping. The required electric power was 7 to 8 watts and pump flow was maintained at 4 L/min. The calf was in excellent condition. Liver and renal function were maintained, plasma free hemoglobin was kept at less than 4 mg/dl (3.3 +/- 0.3 mg/dl), and lactate dehydrogenase was 1043 +/- 36 units/L. In this experimental series, all five pumps passed the 2 week implantation. Two week ex vivo test results indicated very slight thrombus in the hub areas of some pumps. For the next phase of the implantation study, minor design optimization is necessary to completely eliminate thrombus formation. According to our step by step approach, the in vivo test aiming for long-term implantation is ongoing.     

Ploidy results in prostatic carcinoma vary with sampling method and with cytometric technique

A cooperative effort between Baylor College of Medicine and NASA/Johnson Space Center is under way to develop an implantable left ventricular assist device for either pulmonary or systemic circulatory support for more than 3 months' duration. Using methodical evaluation and testing, an implantable axial pump has been systematically improved. These improvements include the addition of an inducer as a pumping element in front of the impeller and the construction of an efficient brushless direct current motor. To date, less than 10 W of power is required to generate 5 L/min flow against 100 mm Hg. An index of hemolysis of 0.021 g/100 L has been achieved. Two-day in vivo feasibility studies in calves are under way to evaluate the antithrombogenic nature of the pump. Further improvements in system efficiency, hemolytic performance, and the antithrombogenic nature of the pump are expected with the use of empirical studies, computer flow modeling, and in vivo testing in calves.     

H3液压系统分析

介绍了穿轧机导盘的主要功能及其匀速转动的意义,对驱动导盘的液压系统——H3的工作原理,并对典型的变量泵定量马达容积闭式回路作了较详细的分析。     

机械、摩擦双防松锁紧装置在单级单吸离心泵中的应用

本文通过对常用单级单吸离心泵叶轮防松方式的研究,发现微动磨损是造成常用叶轮防松装置松动的主要原因,提出了一种避免微动磨损的新的叶轮防松方案,并在煤化工厂的单级泵上进行了试用,取得了较好的效果,该防松方式可以在相关泵上推广使用。     

Long-term in vivo left ventricular assist device study with a titanium centrifugal pump

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart, 2 week screening tests for antithrombogenicity, and 1 month system feasibility. Based on these results, a metallic prototype, Gyro PI 702, was subjected to in vivo left ventricular assist device (LVAD) studies. The pump system employed the Gyro PI 702, which has the same inner dimensions and the same characteristics as the Gyro PI 601, including an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI 702 is driven with the Vienna DC brushless motor actuator. For the in vivo LVAD study, the pump actuator package was implanted in the preperitoneal space in two calves, from the left ventricular apex to the descending aorta. Case 1 achieved greater than 9 month survival without any complications, at an average flow rate of 6.6 L/min with 10.2 W input power. Case 2 was killed early due to the excessive growth of the calf, which caused functional obstruction of the inlet port. There was no blood clot inside the pump. During these periods, neither case exhibited any physiologic abnormalities. The PI 702 pump gives excellent results as a long-term implantable LVAD.     

In vitro and in vivo assessment of an intravenous axial flow pump for right heart assist

Right ventricular (RV) function is a limiting factor in maintaining systemic circulation with circulatory assist. There is, however, no easy way to institute RV assist, such as the intraarterial axial flow pump (Hemopump) used for left heart assist. In this study, the feasibility and hemodynamic effect of intravenous use of an axial flow pump was examined. A pump system was developed with an outflow cannula and an impeller that were newly designed for intravenous insertion with a Hemopump driving system. The pump system characteristics using goat blood at a hematocrit of 26% indicated that maximum flow at a pressure differential against 40 mmHg is 3.2 l/min at a pump speed of 28,000 rpm. The pump was tested in adult goats by intravenous insertion through a 14 mm, low porosity graft anastomosed to the infrarenal inferior vena cava. The pump was advanced until the tip of the cannula was positioned at the main pulmonary artery, using balloon catheter guidance under fluoroscopy. RV assistance was evaluated by pressure tracing, and aortic flow (AF) measured by electromagnetic flowmeter under 1) induced pulmonary stenosis (PS), and 2) electrically induced ventricular fibrillation (VF) in combination with left heart assist. Under PS, right atrial pressure decreased from 11 to 2 mmHg and AF increased from 1.0 to 4.1 l/min after initiation of the pump. Under VF, AF and aortic pressure were 2.6 l/min and 78 mmHg, respectively, with left ventricular assist. After initiation of the pump, they increased to 4.0 l/min and 98 mmHg, respectively. In chronic experiments using three adults goats for up to 48 hr, levels of plasma hemoglobin and platelet counts were maintained within an acceptable range. There was no prominent damage to the hearts. These data suggest that an axial flow pump introduced by an intravenous approach without thoracotomy is feasible and provides sufficient right heart assist.