Hemolysis is one of the main complications associated with the use of ventricular assist devices. The primary factors influencing hemolysis include the shear stress and exposure time experienced by red blood cells. In addition, factors such as local negative pressure and temperature may also impact hemolysis. The different combinations of hemolysis prediction models and their empirical constants lead to significant variations in prediction results; compared to the power-law model, the OPO model better accounts for the complexity of turbulence. In terms of improving hemolytic performance, research has primarily focused on optimizing blood pump structures, such as adjustments to pump gaps, impellers, and guide vanes. A small number of scholars have studied hemolytic performance through control modes of blood pump speed and the selection of blood-compatible materials. This paper reviews the main factors influencing hemolysis, prediction methods, and improvement strategies for rotary blood pumps, which are currently the most widely used. It also discusses the limitations in current hemolysis research and provides an outlook on future research directions.
The purpose of this paper is to report the research and design of control system of magnetic coupling centrifugal blood pump in our laboratory, and to briefly describe the structure of the magnetic coupling centrifugal blood pump and principles of the body circulation model. The performance of blood pump is not only related to materials and structure, but also depends on the control algorithm. We studied the algorithm about motor current double-loop control for brushless DC motor. In order to make the algorithm adjust parameter change in different situations, we used the self-tuning fuzzy PI control algorithm and gave the details about how to design fuzzy rules. We mainly used Matlab Simulink to simulate the motor control system to test the performance of algorithm, and briefly introduced how to implement these algorithms in hardware system. Finally, by building the platform and conducting experiments, we proved that self-tuning fuzzy PI control algorithm could greatly improve both dynamic and static performance of blood pump and make the motor speed and the blood pump flow stable and adjustable.
Heart failure is a leading cause of death in human populations. Because of the insufficient numbers of donor hearts, ventricular assist as a way for the treatment of heart failure and its clinical use is increasing. Initially ventricular assist devices were approved as a bridge-to-recovery indication, and these systems are now increasingly being used as a bridge-to-transplant (BTT) , destination therapy (DT) or permanent support. According to the different structure and working mechanism, ventricular assist device is generally divided into three generation. This review makes a summary on the type of blood pump and its research progress in clinical application.
Objective To provide a ventricular assist device for patients with heart failure, Fu Wai （FW） axial blood pump was developed for partly or totally to assist the left ventricular function. Vitro hemolysis and animals tests were also employed to test the hydromechanics and hemocompatibility of the FW left ventricular assist devices developed in Fu Wai hospital. Methods Using vitro test loop, FW axial blood pump has been used to evaluate the performance of hemolysis， the pump has also been tested for hemolysis characteristic through five sheep experiments. Results At 8 400 r/min, the pump generates 5 L/min flow against 100 mm Hg, the normalized index of hemolysis (NIH) was0.17±0.06 mg/L. The plasma free hemoglobin of in vivo tests was around 30 mg/dl. Conclusion The results obtained in vitro and in vivo testing indicate an acceptable design for the blood pump, further in vivo tests will be performed before clinical use.
The high rotational speed of the axial flow blood pump and flow separation of the centrifugal blood pump are the main causes for blood damage in blood pump. The mixed flow blood pump can effectively alleviate the high rotational speed and the flow separation. Based on this, the purpose of this study is to explore the performance of the mixed blood pump with a closed impeller. A mixed flow blood pump with closed impeller was studied by numerical simulation in this paper. The flow field characteristics and the pressure distribution of this type of blood pump were analyzed. The hydraulic performance of the blood pump and the possible damages to red blood cells were also discussed. At last, pump performance was compared with the mixed flow blood pump with semi-open impeller. The results show that the mixed flow blood pump with close impeller studied in this paper can operate safely and efficiently with a good performance. The pump can reach the pressure head of 100 mmHg at 5 L/min mass flow rate. Flow in the blood pump is uniform and no obvious separation or vortex occurs. Pressure distribution in and on the impeller is uniform and reasonable, which can effectively avoid the thrombosis of blood. The average mean value of hemolysis index is 4.99 × 10−4. The pump has a good biocompatibility. Compared with the mixed flow blood pump with semi-open impeller, the mixed flow blood pump with closed impeller has higher head and efficiency, a smaller mean value of hemolysis index prediction, a better hydraulic performance and the ability to avoid blood damage. The results of this study may provide a basis for the performance evaluation of the closed impeller mixed flow blood pump.
Red blood cells are destroyed when the shear stress in the blood pump exceeds a threshold, which in turn triggers hemolysis in the patient. The impeller design of centrifugal blood pumps significantly influences the hydraulic characteristics and hemolytic properties of these devices. Based on this premise, the present study employs a multiphase flow approach to numerically simulate centrifugal blood pumps, investigating the performance of pumps with varying numbers of blades and blade deflection angles. This analysis encompassed the examination of flow field characteristics, hydraulic performance, and hemolytic potential. Numerical results indicated that the concentration of red blood cells and elevated shear stresses primarily occurred at the impeller and volute tongue, which drastically increased the risk of hemolysis in these areas. It was found that increasing the number of blades within a certain range enhanced the hydraulic performance of the pump but also raised the potential for hemolysis. Moreover, augmenting the blade deflection angle could improve the hemolytic performance, particularly in pumps with a higher number of blades. The findings from this study can provide valuable insights for the structural improvement and performance enhancement of centrifugal blood pumps.
Abstract： Among all kinds of heart diseases, heart failure is the leading cause of death. In recent years, the treatment of terminal heart failure has increasingly become a great challenge to cardiovascular clinical physicians. The limitations of routine medical therapy and surgical interventions, and the shortage of donor hearts have led to the rapid development of mechanical circulation support devices. As the joint research and development of electric machine, mechanical engineering, fluid mechanics, materials science, medical science and some other related subjects, exploring a new type of longterm implantable blood pump has become a hot issue. Axial flow blood pump has the advantages of simple structure, light weight, high flow and efficiency, easy implantation and removal, and at the same time, it does not need to install artificial valves, which can greatly reduce the risk of thrombosis. Compared with the centrifugal pump, axial flow blood pump is smaller and causes much less damage to the blood. At present, axial flow blood pump research has become a focus in cardiac surgery and biomedical engineering field. This article is going to review the operation principles and characteristics of axial flow blood pump, and some key technical issues of current axial flow blood pump research.
Interventional micro-axial flow blood pump is widely used as an effective treatment for patients with cardiogenic shock. Hemolysis and coagulation are vital concerns in the clinical application of interventional micro-axial flow pumps. This paper reviewed hemolysis and coagulation models for micro-axial flow blood pumps. Firstly, the structural characteristics of commercial interventional micro-axial flow blood pumps and issues related to clinical applications were introduced. Then the basic mechanisms of hemolysis and coagulation were used to study the factors affecting erythrocyte damage and platelet activation in interventional micro-axial flow blood pumps, focusing on the current models of hemolysis and coagulation on different scales (macroscopic, mesoscopic, and microscopic). Since models at different scales have different perspectives on the study of hemolysis and coagulation, a comprehensive analysis combined with multi-scale models is required to fully consider the influence of complex factors of interventional pumps on hemolysis and coagulation.
Abstract: The ventricle assist device has emerged as an important therapeutic option in the treatment of both acute and chronic heart failure. The blood pumps which are the major components of ventricle assist devices have also progressed to the third generation. The magnetic and/or liquid levitation technologies have been applied into the third generation blood pumps. The impellers which drive blood are levitated in the blood pumps. The third generation blood pumps are mainly composed of the levitation system and the driving system. The development of the third generation blood pumps has three stages: the stage of foreign motor indirectly driving the impeller with the levitation and driving system separated, the stage of motor directly driving the impeller with the levitation and driving system separated, and the stage of levitation system integrated with the driving system. As the impellers do not contact with other structures, the third generation blood pumps possess the advantages of low thrombosis, less hemolysis and high energy efficiency ratio. Currently most of the third generation blood pumps are in the research stage, but a few number of them are used in clinical trials or applying stage. In this article, the history, classification, mechanism and research situation of the third generation blood pumps are reviewed.
The implantable miniaturized axial blood pump works at a high rotational speed, which increases the risk of blood damage. In this article, we aimed to reduce the possibility of hemolysis and thrombosis by designing a two-stage axial blood pump. Under the operation conditions of flow rate 5 L/min and outlet pressure of 100 mm Hg, we carried out the numerical simulation on the two-stage and single-stage blood pumps to compare the hemolysis and platelet activation state. The results turned out that the hemolysis index of two-stage axial blood pump was better while the platelet activation state was worse than those of single stage design. On the index of hemolysis level and platelet activation state, the design of the two-stage pump with the low and high-head impeller combination was better than the two-stage pump with the equal heads, or the high and low-head impeller combination. In terms of reducing the risk of blood damage for implantable miniaturized axial blood pump, the research result can provide some theoretical basis and new design ideas.