Nonpulsatile Blood Pump Research Articles

Non Invasive Evaluation of the Renal blood flow during left ventricular assistance with the Non-pulsatile blood pump

Non Invasive Evaluation of the Renal blood flow during left ventricular assistance with the Non-pulsatile blood pump

Description of a Flow Optimized Oxygenator With Integrated Pulsatile Pump

Extracorporeal membrane oxygenation (ECMO) is a well-established therapy for several lung and heart diseases in the field of neonatal and pediatric medicine (e.g., acute respiratory distress syndrome, congenital heart failure, cardiomyopathy). Current ECMO systems are typically composed of an oxygenator and a separate nonpulsatile blood pump. An oxygenator with an integrated pulsatile blood pump for small infant ECMO was developed, and this novel concept was tested regarding functionality and gas exchange rate. Pulsating silicone tubes (STs) were driven by air pressure and placed inside the cylindrical fiber bundle of an oxygenator to be used as a pump module. The findings of this study confirm that pumping blood with STs is a viable option for the future. The maximum gas exchange rate for oxygen is 48mL/min/L(blood) at a medium blood flow rate of about 300mL/min. Future design steps were identified to optimize the flow field through the fiber bundle to achieve a higher gas exchange rate. First, the packing density of the hollow-fiber bundle was lower than commercial oxygenators due to the manual manufacturing. By increasing this packing density, the gas exchange rate would increase accordingly. Second, distribution plates for a more uniform blood flow can be placed at the inlet and outlet of the oxygenator. Third, the hollow-fiber membranes can be individually placed to ensure equal distances between the surrounding hollow fibers.

In Vitro Evaluation of the Performance of Korean Pulsatile ECLS (T-PLS) Using Precise Quantification of Pressure-Flow Waveforms

The Twin-Pulse Life Support System (T-PLS) is a novel pulsatile extracorporeal life support system developed in Korea. It has been reported that the T-PLS achieves higher levels of tissue perfusion of the kidney during short-term extracorporeal circulation and provides more blood flow to coronary artery than nonpulsatile blood pumps. However, these results lack pulsatility quantifications and thus make it hard to analyze the effects of pulsatility upon hemodynamic performance. We have adopted the concepts of hemodynamic energy, energy equivalent pressure (EEP), and surplus hemodynamic energy (SHE) to evaluate pulsatility performance in the different circuit configurations of the T-PLS and a membrane oxygenator (MO) in vitro. In a mock system, three different circuits were constructed depending on the location of an MO: pump-MO-pump (serial), MO-pumps (parallel A), and pumps-MO (parallel B). In parallel A, a low-resistance MO was used to preserve the pulsatility from the pump. All circuits showed good pulsatility in terms of EEP (serial: 13.2% +/- 3.2%, parallel A: 10.0% +/- 1.6%, parallel B: 7.00% +/- 1.1%; change from aortic pressure to EEP; p < 0.003). The SHE levels were 17,404 +/- 3750 ergs/cm3, 13,170 +/- 1486 ergs/cm3, and 9192 +/- 1122 ergs/cm3 in each circuit setup (p < 0.001). Although EEP levels were somewhat lower, both parallel types provided higher pump output compared with the serial type (serial: 1.87 +/- 0.29 l/min, parallel A: 3.09 +/- 0.74 l/min, parallel B: 3.06 +/- 0.56 l/min; p < 0.003 except parallel A vs. parallel B, p = 0.90). Conclusively, the precise quantifications of pressure flow waveforms, EEP, and SHE are valuable tools for evaluating pulsatility of the mechanical circulatory devices, and are expected to be used as additional performance indexes of a blood pump. The pulsatility performances are different according to circuit setups. However, the parallel A circuit could achieve higher pump output and generate adequate pulsatility level. Thus, the parallel A circuit is suggested as the optimal configuration in T-PLS applications.

Application of a Pressure‐relieving Air Compliance Chamber in a Single‐pulsatile Extracorporeal Life Support System: An Experimental Study

Nonpulsatile blood pumps are mainly used in extracorporeal life support systems. Although pulsating blood flow is known to be physiological, a pulsatile pump is not commonly applied in a circuit with a membrane oxygenator because of damage to the blood cells. The hypothesis that the placement of a pressure-relieving compliance chamber in a circuit might reduce blood cell trauma was tested. An extracorporeal life support circuit was constructed in an acute lung injury model of dogs by oleic acid infusion. The animals were divided into three groups. In group I (n = 6) a nonpulsatile centrifugal pump was used as a control. In group II (n = 4) a single-pulsatile pump was used, and in group III (n = 6) a single-pulsatile pump equipped with a compliance chamber was used. Pump flow was maintained at 1.8-2.0 L/min for 2 h. Hemodynamics and blood gas analyses indicated that the pulsatile groups II and III had better results than the nonpulsatile group I. The plasma-free hemoglobin level, which indicates blood cell trauma, was the lowest in group I and the highest in group II but was significantly decreased in group III. A pressure-relieving compliance chamber could significantly reduce high circuit pressures and blood cell trauma.

STATUS OF MAGNETICALLY SUSPENDED MiTiHeart?? LVAD

The MiTiHeart® LVAD is a non-pulsatile rotary blood pump that uses a hybrid passive/active magnetic bearing support system and exhibits low-hemolysis, low power loss, low vibration, and high reliability. Unique features include a simple and direct flow path for both main and washing blood flows, non-contact pump rotor, i.e., no rubbing surfaces, and relatively large clearances between the pump rotor and housing. The first prototype was constructed from medical grade polycarbonate. To reduce the possibility of thrombosis, the internally exposed surfaces were coated with a biocompatible polymer. Hemolysis testing, with bovine blood, was performed at the Hershey Medical Center at Pennsylvania State University. Test results showed a low normalized index of hemolysis of 0.01 mg/100 L. An acute animal test and a chronic 200-hour implant were successfully completed at the Hershey Medical Center. In these tests, the pump was implanted in a calf and operated in parallel with the heart A second prototype was constructed using a titanium alloy for all blood contacting surfaces and incorporating a redundant hydrodynamic thrust bearing. This addition; however, required careful assessment of blood flow and potential hemolysis in narrow passages. A novel methodology, which combines the existing hemolysis models with the principles of fluid dynamics for quantitative prediction of the rate of blood damage was used. A second prototype was implanted in a calf in a chronic test. The results of this evaluation plus results of in vitro performance tests will be presented

Testing of a centrifugal blood pump with a high efficiency hybrid magnetic bearing.

The purpose of this article is to present test results for a second generation, high efficiency, nonpulsatile centrifugal blood pump that is being developed for use as a left ventricular assist device (LVAD). The LVAD pump uses a hybrid passive-active magnetic bearing support system that exhibits extremely low power loss, low vibration, and high reliability under transient conditions and varying pump orientations. A unique feature of the second generation design configuration is the very simple and direct flow path for both main and washing blood flows. The pump was tested in both vertical and horizontal orientations using a standard flow loop to demonstrate the performance and durability of the second generation LVAD. Steady state and transient orientation pump operating characteristics including pressure, flow, speed, temperatures, vibration, and rotor orientation were measured. During the tests, pump performance was mapped at several operating conditions including points above and below the nominal design of 5 L/min at 100 mm Hg pressure rise. Flow rates from 2 to 7 L/min and pressure rises from 50 to 150 mm Hg were measured. Pump speeds were varied during these tests from 2,500 to 3,500 rpm. The nominal design flow of 5 L/min at 100 mm Hg pressure rise was successfully achieved at the design speed of 3,000 rpm. After LVAD performance testing, both 28 day continuous duty and 5 day transient orientation durability tests were completed without incident. A hydrodynamic backup bearing design feasibility study was also conducted. Results from this design study indicate that an integral hydrodynamic backup bearing may be readily incorporated into the second generation LVAD and other magnetically levitated pump rotors.

IN VIVO STUDY OF AN LVAD PROTOTYPE WITH A HYBRID MAGNETIC BEARING

A second-generation prototype of a high efficiency, non-pulsatile rotary blood pump was developed for use as a left ventricular assist device (LVAD). The LVAD pump uses a hybrid passive/active magnetic bearing support system which exhibits low power losses, low vibration, and high reliability under transient conditions and varying pump orientations. Unique features of the design are the simple and direct flow path for both main and washing blood flows, the non-contact pump rotor, i.e., no rubbing surfaces, and relatively large clearances (≥ 5 mm) between the pump rotor and housing. The prototype was constructed from medical grade polycarbonate. To reduce the possibility of thrombosis, the internally exposed surface area was coated with a biocompatible polymer. The purpose of this study was to determine the in vivo form, fit and function of the pump in a calf model. Hemolysis testing, with bovine blood, was performed at the Hershey Medical Center of Pennsylvania State University. The test results showed a low normalized index of hemolysis of 0.05 g/100 L. Encouraged by these results, an acute animal test was successfully completed at the Hershey Medical Center. During the test, the pump was implanted in a calf and operated in parallel with the calf's heart. Following the acute test a chronic implant study was completed. The results of these in vivo tests are discussed.

T-PLS NEW PULSATILE BLOOD PUMP TECHNOLOGY FROM CARDIAC ARREST TO HEART RECOVERY

The conventioal non-pulsatile blood pump of the roller-type or the centrifugal pump are used for present ECMO application. We have developed the Twin Pulse Life Support (T- PLS) and performed animal experiments. As T- PLS is a portable device with small size, it can he used, sequencially, from the emergency care to the surgical operation and the patients recovery. The T- PLS system consists of two blood sac and oxygenator. The polypropylene hollow fiber membrane oxygenator (Univoxtm- IC, Baxter) was used. The polyurethane polymer valves are used at the inlet and outlet sides of the tubular blood sacs. Non- pulsatile ECMO system as centrifugal pump may generate negative pressure as high 2s − 200 to − 700 mmHg in the drainage circuit which may cause cavitation, and the pump output are independent upon the afterload However, T- PLS flow's pre-load dependency and after-load-independent pump output can make the system to he automatically controlled In animal experiments, the degree of the blood damages was lower than the other conventional pumps. These animal and in-vitro experimental results show that the pulsatile flow can be safely produced for physiological blood flows in the brain, heart, and the lung.

The seventh prototype of the mini-spindle-pump: does it fulfill the expectations of a short-term pump?

According to recent trends to develop implantable nonpulsatile blood pumps for different function modes and times, our intention was and still is to build a Mini-Spindle-Pump for a pumping duration of about 14 days. Initial conception for this plan was the premise that the device in a mock circuit should move 4 L of water/min at a speed of 12,000 to 15,000 rpm against a pressure difference of 90 mm Hg between pump inlet and outlet. Despite the development of 6 different prototypes, this project was not realized. Under the above-mentioned conditions, the main problem of this type of blood pump, the blood trauma, could not be reduced to an adequate level, i.e., the Mini-Spindle-Pump is not a high speed pump. Therefore, a revision of the conception was necessary. The device in a mock circuit should transport 5 L of water/min at a speed of about 9,000 rpm against a pressure difference of 90 mm Hg between its inlet and outlet. Considering the implantability of the blood pump, the following measurements for its components were arrived at. The U-shaped blockformed plexiglas housing was enlarged to 120 x 40 x 40 mm (length of blood chamber 86 mm, inner diameter 27 mm), and the rotor with 5 windings was redesigned at a length of 64 mm (outer diameter 25 mm, inner diameter 6.7 mm). In a mock circuit, this 7th prototype transported with a speed of 9,000 rpm about 10 L of water/min at an afterload of 80 mm Hg. In acute animal experiments with calves up to 15 h of pumping duration, the device showed the expected efficiency. Experiments with a longer pumping duration are necessary to confirm that this prototype will fulfill the criteria of a short-term pump according to Dr. Y. Nosé's advice.

Analysis of the relationship between left ventricular pressure and motor current for evaluation of native cardiac function during left ventricular support with a centrifugal blood pump

Control of the ventricular assist device (VAD) for native heart preservation should be attempted, and the VAD could be one strategy for dealing with the shortage of donors in the future. In the application of nonpulsatile blood pumps for ventricular assistance from the ventricular apex to the aorta, bypass flow and hence the motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous-flow pumps, in this study we investigated whether motor current could be used as an index for continuous monitoring of native cardiac function. In study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mmHg, afterload of 40 mmHg, and LV systolic pressure of 40 mmHg was used. The pump speed was fixed at 1300, 1500, and 1700 rpm, and LV systolic pressure was increased up to 140 mmHg by steps of 20 mmHg while the changes in LV pressure, motor current, pump flow, and aortic pressure were observed. In study 2, an in vivo experiment was performed using three sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LVP was varied through administration of dopamine while the changes in LV pressure, pump flow, and motor current at 1500 and 1700 rpm were observed. An excellent correlation was observed in both in vitro and in vivo studies in the relationship between motor current and LV pressure. In study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1300, 1500, and 1700 rpm, respectively. In study 2, they were 0.88 (animal no. 1), 0.83 (animal no. 2), and 0.88 (animal no. 3) for 1500 rpm, and 0.95 (animal no. 2) and 0.93 (animal no. 3) for 1700 rpm. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VAD for native heart preservation.

Did Ündar and Associates Really Make Those Comments on the Issue of Pulsatile Versus Nonpulsatile Flow? Absolutely Not.

Did Ündar and Associates Really Make Those Comments on the Issue of Pulsatile Versus Nonpulsatile Flow? Absolutely Not.

Motor Current Waveforms as an Index for Evaluation of Native Cardiac Function During Left Ventricular Support with a Centrifugal Blood Pump

Control of ventricular assist devices (VADs) for native heart preservation should be attempted, and it could be one strategy for dealing with the shortage of donors in the future. In the application of a nonpulsatile blood pump for ventricular assistance from its apex to the aorta, the bypass flow and hence motor current of the pumps change in response to the ventricular pressure change. Utilizing these intrinsic characteristics of the continuous flow pumps, this study investigated whether or not motor current could be used as an index for continuous monitoring of native cardiac function. In Study 1, a centrifugal blood pump (CFP) VAD was installed between the apex and descending aorta of a mock circulatory loop. In this model, a baseline with a preload of 10 mm Hg, afterload of 40 mm Hg, and left ventricular (LV) systolic pressure of 40 mm Hg was used. The pump rpm were fixed at 1,300, 1,500, and 1,700, and LV systolic pressure was increased up to 140 mm Hg by a step of 20 mm Hg while observing the changes in LV pressure, motor current, pump flow, and aortic pressure. In Study 2, in vivo experiments were performed using 5 sheep. A left heart bypass model was created using a centrifugal pump from the ventricular apex to the descending aorta. The LV pressure was varied through administration of dopamine while observing the changes in LV pressure, pump flow, motor current, and aortic pressure at 1,500 and 1,700 rpm. An excellent correlation was observed both in vitro and in vivo studies in the relationship between motor current and LV pressure. In Study 1, the correlation coefficients were 0.77, 0.92, and 0.99 for 1,300, 1,500, and 1,700 rpm, respectively. In Study 2, they were 0.90 (Animal 1), 0.82 (Animal 2), 0.89 (Animal 3), 0.93 (Animal 4), and 0.70 (Animal 5) respectively for 1,500 rpm, and 0.94 (Animal 2), 0.85 (Animal 3), 0.94 (Animal 4), and 0.89 (Animal 5) respectively, for 1,700 rpm. The relationship between motor current and pump flow and LV pressure showed an unstable correlation in an in vivo study. These results suggest that motor current amplitude monitoring could be useful as an index for the control of VADs for native heart preservation.

Influence of Pulsatile and Nonpulsatile Left Heart Bypass on the Hormonal Circadian Rhythm

Influence of Pulsatile and Nonpulsatile Left Heart Bypass on the Hormonal Circadian Rhythm

【基調講演】人工心臓開発の最近の動向(OS-7)

We have been developing two types of next-generation, a pulsatile totally implantable artificial heart and a nonpulsatile centrifugal blood pump (CP). The pulsatile device is an electrohydraulic artificial heart with right and left di aphragm type artificial ventricles activated alternately by an intracorporeal regenerative pump as an actuator. The nonpulsatile device is a no-seal and no-shaft CP featuring self-irrigation of an impeller. The feasibility of the pumps was assessed. The results indicated that these pumps fulfilled basic requirements for a long-term device although est ablishment of adequate control is necessary to overcome changes of hemodynamics in a living body. Pathophysiology of recipients of such devices were analyzed and new technologies to carry out research and development of the arti ficial hearts were efficiently applied.

Development of rotary blood pump technology: past, present, and future.

Even though clinical acceptance of a nonpulsatile blood flow was demonstrated almost 45 years ago, the development of a nonpulsatile blood pump was completely ignored until 20 years ago. In 1979, the first author's group demonstrated that completely pulseless animals did not exhibit any abnormal physiology if 20% higher blood flows were provided to them. However, during the next 10 years (1979-1988), minimum efforts were provided for the development of a nonpulsatile, permanently implantable cardiac prosthesis. In 1989, the first author and his team at Baylor College of Medicine initiated a developmental strategy of various types of nonpulsatile rotary blood pumps, including a 2-day rotary blood pump for cardiopulmonary bypass application, a 2 week pump for ECMO and short-term circulatory assistance, a 2 year pump as a bridge to transplantation, and a permanently implantable cardiac prosthesis. Following the design and developmental strategy established in 1989, successful development of a 2-day pump (the Nikkiso-Fairway cardiopulmonary bypass pump) in 4 years (1989-1993), a 2 week pump (Kyocera gyro G1E3 pump) in 6 years (1992-1998), and a bridge to transplant pump (DeBakey LVAD-an axial flow blood pump) in 10 years (1988-1998) was made. Currently, a permanently implantable centrifugal blood pump development program is successfully completing its initial Phase 1 program of 5 years (1995-2000). Implantation exceeded 9 months without any negative findings. An additional 5 year Phase II program (2000-2005) is expected to complete such a device that will be clinically available.

Development of a non-pulsatile permanent rotary blood pump

For many years, a common belief was that non-pulsatile perfusion produced physiological and circulatory abnormalities. Since 1977 our group has reported, if a 20% higher blood flow was used more than required for a pulsatile blood pump, there would be no circulatory or physiological abnormalities. These experimental findings confirmed that there was no difference in clinical outcome when using a pulsatile or non-pulsatile blood pump. Furthermore, the non-pulsatile rotary blood pump has demonstrated efficient and reliable performance in various clinical situations. The non-pulsatile blood pump is a simple and reliable design, that can be easily manufactured, and has the following desirable features. There is no need to incorporate heart valves, a large orifice inflow conduit, or a compliance volume-shifting chamber. Since an electrical motor operates continuously, the on-and-off motion required for a pulsatile pump is not necessary; therefore, it becomes a more efficient and durable system. Further, the control algorism is simpler and more reliable than a pulsatile pump. Considering these factors, the non-pulsatile blood pump can be selected for a permanently implantable assist device. To develop an implantable non-pulsatile cardiac device, it is necessary to incorporate seven features in the system such as: small size, atraumatic features, anti-thrombogenic features, anti-infection features, durable and simple design, and low energy requirement with easy controllability.

Can We Develop a Nonpulsatile Permanent Rotary Blood Pump? Yes, We Can.

For many years, it was thought that nonpulsatile perfusion produced physiological and circulatory abnormalities. Since 1977, Yukihiko Nosé and his colleagues have challenged this misconception. Toward that end, they did show that if a 20% higher blood flow uses more than that required for a pulsatile blood pump, then there would be no circulatory or physiological abnormalities. These experimental findings confirm that there is no difference in clinical outcome using either a pulsatile or nonpulsatile blood pump. Furthermore, the nonpulsatile rotary blood pump demonstrates efficient and reliable performance in various clinical situations. The nonpulsatile blood pump is a simple and reliable design that is manufactured easily and that has several desirable features. There is no need to incorporate heart valves, which are the most thrombogenic and blood trauma-inducing component. A continuous flow pump does not require a large orifice inflow conduit and proves to be easier to implant in patients with minimal damage to the myocardium. There is no need to incorporate a compliance volume-shifting device, which is essential for a pulsatile blood pump. The nonpulsatile device is a continuous blood pumping system; therefore, the control system is simpler and more reliable than that of a pulsatile pump. Because of the rotary blood pump's structure, only one moving part is necessary for the blood-pumping motion. By using durable components for this moving part, a durable system becomes possible. Because the electrical motor operates continuously, the on-and-off motion required for a pulsatile pump is not necessary; therefore, it is a more efficient and durable system. Thus, this group is working on the development of a nonpulsatile blood pump as a permanently implantable assist device. To achieve this goal, it is necessary to incorporate seven features into the system: small size, atraumatic features, antithrombogenic features, antiinfection features, a simple and durable design, and low energy requirement with easy controllability.

Numerical Simulation of Nonpulsatile Left Ventricular Bypass.

A computer simulation was carried out to investigate the influence of nonpulsatile left ventricular assistance on hemodynamics. A simulation circuit was constructed to represent the circulatory system. A source of current was added to denote the nonpulsatile blood pump. The left and right ventricles were replaced by variable compliances. Left heart failure was simulated by decreasing the amount of compliance change of the left ventricle. We introduced a pulsatility indicator (PI) to clarify the pulsatility characteristics in the hemodynamics; this PI was defined as the ratio of the pulse pressure (PP) to the mean aortic pressure (AoP). When nonpulsatile bypass flow increased, the mean AoP, tension time index (TTI), and diastolic pressure time index (DPTI) increased, and cardiac output, PP, and PI decreased. When assisted flow increased with the constant total flow rate, the mean AoP and DPTI changed little; the PP, TTI, and PI decreased, and the endocardial viability rate increased. The PI would be helpful in evaluating the effect of pulsatility.

Cleveland clinic rotodynamic pump

It is now accepted that 70% to 80% of patients with end-stage heart failure would benefit from a permanent implanted left ventricular assist device. Previously there was little consideration of the use of nonpulsatile pumps for this function. An extensive 5-year engineering research and development program to develop a permanent implanted nonpulsatile blood pump has been undertaken. We have developed a continuous-flow blood pump of small size (207 g) and low power requirement (6.5 watts) producing 5 L/min flow with low hemolysis. This pump has the potential to be the basis of an innovative ventricular assist system.

The valvo-pump, an axial blood pump implanted at the heart valve position: concept and initial results.

The valvo-pump, an axial nonpulsatile blood pump implanted at the heart valve position, has been developed. The valvo-pump consists of an impeller and a motor, which are encased in a housing. An impeller with 5 vanes (22.0 mm in diameter) is used. The impeller is connected to a samarium-cobalt-rare earth magnet direct current (DC) brushless motor measuring 21.3 mm in diameter and 18.5 mm in length. Sealing is achieved by means of a ferrofluidic seal. A pump flow of 10.5 L/min was obtained at a pump differential pressure of 3.3 kPa (25 mm Hg), and a flow of 4.9 L/min was obtained at 7.0 kPa (53 mm Hg). Sealing was kept perfect against a pressure of 29.3 kPa (220 mm Hg) at 9,000 rpm.