Query: "open vane" centrifugal blood pump

title: 525 Flow visualization for open vane centrifugal blood pump

title: Flow visualization for open vane centrifugal blood pump

title: Mechanical antithrombogenic properties by vibrational excitation of the impeller in a magnetically levitated centrifugal blood pump.
abstract: Mechanical circulatory support devices have been used clinically for patients with heart failure for over ten years. However, thrombus formation inside blood pumps remains a risk to patient life, causing pump failure and contributing to neurological damage through embolization. In this paper, we propose a method for preventing thrombus formation by applying vibrational excitation to the impeller. We evaluate the ability of this method to enhance the antithrombogenic properties of a magnetically levitated centrifugal blood pump and ensure that the impeller vibration does not cause undue hemolysis. First, three vibrational conditions were compared using an isolated pump without a mock circulation loop; the vibrational excitation frequencies and amplitudes for the impeller were set to (i) 0 Hz 0 mm, (ii) 70 Hz 10 mm and (iii) 300 Hz 2.5 mm. The motor torque was measured to detect thrombus formation and obtain blood coagulation time by calculating the derivative of the torque. Upon thrombus detection, the pump was stopped and thrombi size were evaluated. The results showed an increase in the blood coagulation time and a decrease in the rate of thrombus formation in pumps with the impeller vibration. Second, an in vitro hemolysis test was performed for each vibrational condition to determine the effect of impeller vibration on hemolysis. The results revealed that there was no significant difference in hemolysis levels between each condition. Finally, the selected vibration based on the above test results and the non vibration as control were compared to investigate antithrombogenic properties under the continuous flow condition. The blood coagulation time and thrombi size were investigated. As a result, vibrational excitation of the impeller at a frequency of 300 Hz and amplitude of 2.5 mm was found to significantly lengthen clotting time, decreasing the rate of pump thrombus compared to the non vibration condition. We indicate the potential of impeller vibration as a novel mechanical antithrombogenic mechanism for rotary blood pumps. This article is protected by copyright. All rights reserved.

title: Flow rate estimation of a centrifugal blood pump using the passively stabilized eccentric position of a magnetically levitated impeller
abstract: Flow rate estimation for ventricular assist devices without additional flow sensors can improve the quality of life of patients. In this article, a novel flow estimation method using the passively stabilized displacement of a magnetically levitated impeller is developed to achieve sufficient accuracy and precision of flow estimation for ventricular assist devices in a simple manner. The magnetically levitated impeller used is axially suspended by a magnetic bearing in a centrifugal blood pump that has been developed by our group. The radial displacement of the impeller, which is restricted by passive stability, can be correlated with the flow rate because the radial hydraulic force on the impeller varies according to the flow rate. To obtain the correlation with various blood viscosities, the relationships between the radial displacements of the magnetically levitated impeller and the pressure head flow rate characteristics of the pump were determined simultaneously using aqueous solutions of glycerol with a potential blood viscosity range. The measurement results showed that accurate steady flow rates could be estimated with a coefficient of determination of approximately 0.97 and mean absolute error of approximately 0.22 L/min without fluid viscosity measurements by using the relationships between the impeller displacement and the flow rate. Moreover, a precision of approximately 0.01 (L/min)/um was obtained owing to a strong estimation indicator signal provided by the large displacement of the passively stabilized impeller; thus, the proposed estimation method can help ensure sufficient accuracy and precision for ventricular assist devices in a simple manner, even if the blood viscosity is unknown.

title: Multi Objective Genetic Algorithm Assisted by an Artificial Neural Network Metamodel for Shape Optimization of a Centrifugal Blood Pump.
abstract: A centrifugal blood pump is a common type of the pump used as a left ventricular assist device (LVAD) in the medical industries. The reduction of the LVADs hemolysis level to reduce the blood damage is one of the major concerns in designing of such devices. Also, the enhancement of the LVADs efficiency to decrease the battery size is another design requirement. The blood damage critically depends on the state of the blood being pumped. Besides the blood state, the blood damage also depends on the pump impeller and volute geometries. In this research, a multi objective optimization of a centrifugal blood pump is performed. A complete 3D optimization platform is established for both impeller and volute of a centrifugal blood pump consisting of parametric modeling, automatic mesh generation, computational fluid dynamics (CFD) simulation, and optimization strategy. A vast number of cases with various impeller and volute shapes are numerically simulated. Three different metamodels are created using artificial neural networks (ANNs) in order to approximate the pump hydraulic efficiency, hemolysis index (HI) and pressure head. The inverse of the relative pressure head is defined as the first objective and the summation of relative hemolysis index and the inverse of the relative efficiency is assumed as the second objective. Non dominated Sorting Genetic Algorithm II (NSGA II) is used to find the Pareto Front. A set of optimal points is selected. Finally, for the physiological flow conditions, the optimum design that provides 11.9% HI reduction and 7.2% efficiency enhancement is selected.

title: Flow Characteristics and Coherent Structures in a Centrifugal Blood Pump
abstract: Blood clot formation can be initiated by local flow conditions where regions of high shear and long residence time regions, such as flow separation and stagnation, have been identified as risk factors. This study highlights coherent structures, some of which not yet considered in the literature that may contribute to blood clot formation in the ECMO (Extra Corporeal Membrane Oxygenator) circuit. The centrifugal ECMO pump investigated in this study is compact and delivers adequate volume of blood with relatively high pressure in order to compensate for the large pressure drop in the membrane oxygenator. These requirements lead to regions with high shear in several different parts of the pump. In the narrow gap between the pump house and the impeller body (the magnet) a Taylor Couette like flow is observed with azimuthally aligned wavy vortices, which are also pushed towards the bottom of the pump house by the flow generated by the blades. At the bottom gap between the impeller house and the pump house one finds spiraling flow structures, due to the rotation of the former structure. Separation bubbles are found near the tongue of the pump and at the lee sides of the blades. Such vortical structures have in literature been identified as regions where platelets may be activated whereby clots may develop.

title: Development of a real time and quantitative thrombus sensor for an extracorporeal centrifugal blood pump by near infrared light.
abstract: We developed an optical thrombus sensor for a monopivot extracorporeal centrifugal blood pump. In this study, we investigated its quantitative performance for thrombus detection in acute animal experiments of left ventricular assist using the pump on pathogen free pigs. Optical fibers were set in the driver unit of the pump. The incident light at the near infrared wavelength of 810 nm was aimed at the pivot bearing, and the resulting scattered light was guided to the optical fibers. The detected signal was analyzed to obtain the thrombus formation level. As a result, real time and quantitative monitoring of the thrombus surface area on the pivot bearing was achieved with an accuracy of 3.6 2.3 mm2. In addition, the sensing method using the near infrared light was not influenced by changes in the oxygen saturation and the hematocrit. It is expected that the developed sensor will be useful for optimal anticoagulation management for long term extracorporeal circulation therapies.

title: Shape optimization of a centrifugal blood pump by coupling CFD with metamodel assisted genetic algorithm
abstract: A centrifugal blood pump is a common type of pump used as a left ventricular assist device in the medical industries. Therefore, the improvement of the device bio compatibility to reduce the blood damage and to increase the efficiency has become a major challenge. In the current work, a metamodel assisted genetic algorithm is employed to simultaneously optimize the impeller and volute geometries of a typical centrifugal blood pump. The overall shape of the base design is inspired from HeartMate3 LVAD, and the main dimensions of the base design including inlet and outlet radius, blade angle distribution, volute cross section area distribution, etc. are designed in our laboratory. Three different scenarios are investigated using three different objective functions, i.e. (1) hydraulic efficiency, (2) pressure head, and (3) hemolysis index (HI) The results showed that the shape optimized by pump efficiency has also nearly the same level of HI as the shape optimized by HI. Hence, to reduce computation time, one can use efficiency instead of HI as an objective function. However, one must check the HI level after such optimization to see whether it is within the acceptable range of HI for such bio application.

title: Effect of blade curvature on the hemolytic and hydraulic characteristics of a centrifugal blood pump
abstract: Impeller design has a significant impact on the overall performance of a blood pump. In this study, the effect of the blade curvature was investigated by performing in silico and in vitro studies on a recently developed centrifugal blood pump.  A computational fluid dynamics study was performed for the flow rates of 3 5 L/min at 2000 r/min. The computational fluid dynamics model was also applied on the US Food and Drug Administration (FDA) benchmark blood pump to validate our computational method. The relative hemolysis index was calculated with the Eulerian hemolysis estimation method for five impellers with the wrap angles ranging from 0deg to 240deg. Hydraulic experiments were conducted for the validation of computational fluid dynamics results. In addition, the curved blade impeller (120deg) and the straight blade impeller (0deg) were evaluated with in vitro hemolysis tests using human blood.  The wrap angle of 120deg provided the best hydraulic and hemolytic performance. Pump achieved the physiologic operating pressures and flows with 85 115 mmHg at 2.5 5.9 L/min. Compared to the straight blade impeller, the 120deg model reduces the relative hemolysis index and the plasma free hemoglobin near 72.8% and 56.7% respectively. Comparison of in silico and in vitro results indicated the similar trend to the blade curvature.  Introducing a blade curvature enhanced the hydrodynamic and hemolytic performance compared to the straight blade configuration for the investigated centrifugal blood pump. The findings of this study provide new insights into centrifugal blood pump design by examining the influence of the blade curvature.

title: Development of real time and quantitative monitoring of thrombus formation in an extracorporeal centrifugal blood pump
abstract: We developed an optical detector of thrombus formed on the pivot bearing of an extracorporeal centrifugal blood pump (MERA HCF MP23; Senko Medical Instrument Mfg. Co. Ltd. Tokyo, Japan) which is frequently used for long term extracorporeal circulation support to bridge to an implantable artificial heart, which in turn is used for bridge to heart transplantation in Japan. In this study, we investigated the quantitative performance of the thrombus formation in acute animal experiments. A total of three experiments of extracorporeal left ventricular assist using Japanese specific pathogen free pigs were conducted. The optical fibers were set in the pump driver unit. The incident light at nearinfrared wavelength aiming at the pivot bearing and the resulting scattered light were guided to respective fibers. The detected signal was analyzed to obtain thrombus formation level (TFL) calculated by a specially developed software. When the increase in TFL was confirmed, the pump was exchanged and the extracorporeal circulation was restarted. The number of pump exchanges were four times at each experiment so a total of twelve pumps were evaluated. 3 dimentional data surrounding the pivot bearing and the adhered thrombus was captured by a 3 dimantional surface measurement system to calculate the thrombus surface area (TSA) formed on the pivot bearing. As a result, the correlation coefficient between TFL and TSA was 0.878. The accuracy of TSA estimated by the optical detector was 3.6+ 2.3 mm2. This was small enough to not have the pump exchanged in clinical judgement. The developed detector would be useful for optimal anti coagulation management.