Left ventricular assist devices (LVADs) have been increasingly used as a therapy for patients with end-stage heart failure. However, a growing number of clinical observations have shown that LVADs are associated with thromboembolic events, which are potentially related to the changes in intraventricular flow. Particularly, the flow fields around the inflow cannula (IC) of the LVAD. In this study, a fluid structure interaction (FSI) simulation was conducted to evaluate the hemodynamics of a patient specific left ventricle (LV) with varying LVAD IC orientations. The LV model was obtained from computed tomography scans and modeled to have contraction and relaxation during cardiac cycles following available experimental data of LV volume changes. The LV of the patient was assumed to have an end systolic volume of 223.7 mL and a stroke volume of 46.4 mL. Four different IC positions were considered: towards the (1) septum; (2) aortic valve (AV); (3) mitral valve (MV) and (4) inferior wall (IW). The potential thrombus growth around the IC was assumed to be caused by blood stagnation regions with low velocity (<5 mm/s) and low shear rate (<60/s) flow. Mean velocity magnitudes and low blood velocity regions around the IC were numerically obtained. To quantitatively compare the thrombosis risks of the four simulation cases, the time-averaged volumes of the low-velocity regions and the low shear rate regions were calculated. The intraventricular volumes of low velocity zones based on IC orientation are 1.42 mL toward the septum, 1.14 mL toward the AV, 0.93 mL toward the MV, and 1.24 mL toward the IW. The intraventricular volumes of low shear regions based on IC orientation are 11.54 mL toward the septum, 11.15 mL toward the AV, 9.24 mL toward the MV, and 10.7 mL toward the IW. IC orientation toward the MV results in lower volumetric regions of low flow and low shear within the ventricle, which consequently may lead to a reduced risk of thrombus formation.

Centrifugal blood pumps have become popular for adult extracorporeal membrane oxygenation (ECMO) due to their superior blood handling and reduced thrombosis risk featured by their secondary flow paths that avoid stagnant areas. However, the high rotational speed within a centrifugal blood pump can introduce high shear stress, causing a significant shear-induced hemolysis rate. The Revolution pump, the Rotaflow pump, and the CentriMag pump are three of the leading centrifugal blood pumps on the market. Although many experimental and computational studies have focused on evaluating the hydraulic and hemolytic performances of the Rotaflow and CentriMag pumps, there are few on the Revolution pump. Furthermore, a thorough direct comparison of these three pumps' flow characteristics and hemolysis is not available. In this study, we conducted a computational and experimental analysis to compare the hemolytic performances of the Revolution, Rotaflow, and CentriMag pumps operating under a clinically relevant condition, i.e., the blood flow rate of 5 ​L/min and pump pressure head of 350 ​mmHg, for adult ECMO support. In silico simulations were used to characterize the shear stress distributions and predict the hemolysis index, while in vitro blood loop studies experimentally determined hemolysis performance. Comparative simulation results and experimental data demonstrated that the CentriMag pump caused the lowest hemolysis while the Revolution pump generated the highest hemolysis.

Blood pumps have been increasingly used in mechanically assisted circulation for ventricular assistance and extracorporeal membrane oxygenation support or during cardiopulmonary bypass for cardiac surgery. However, there have always been common complications such as thrombosis, hemolysis, bleeding, and infection associated with current blood pumps in patients. The development of more biocompatible blood pumps still prevails during the past decades. As one of those newly developed pumps, the Breethe pump is a novel extracorporeal centrifugal blood pump with a hybrid magnetic and mechanical bearing with attempt to reduce device-induced blood trauma. To characterize the hydrodynamic and hemolytic performances of this novel pump and demonstrate its superior biocompatibility, we use a combined computational and experimental approach to compare the Breethe pump with the CentriMag and Rotaflow pumps in terms of flow features and hemolysis under an operating condition relevant to ECMO support (flow: 5 L/min, pressure head: ~350 mmHg). The computational results showed that the Breethe pump has a smaller area-averaged wall shear stress (WSS), a smaller volume with a scalar shear stress (SSS) level greater than 100 Pa and a lower device-generated hemolysis index compared to the CentriMag and Rotaflow pumps. The comparison of the calculated residence times among the three pumps indicated that the Breethe pump might have better washout. The experimental data from the in vitro hemolysis testing demonstrated that the Breethe pump has the lowest normalized hemolysis index (NIH) than the CentriMag and Rotaflow pumps. It can be concluded based on both the computational and experimental data that the Breethe pump is a viable pump for clinical use and it has better biocompatibility compared to the clinically accepted pumps.

Objective: Antegrade cerebral perfusion (ACP) is the most common used method of perfusion in aortic arch surgery, but the complication of ACP investigation still have happened. In this paper, we present how to choose an appropriate method of ACP for the individual therapies for individual differences in cerebral blood vessels. Methods: We introduced the method of computational fluid dynamics (CFD) to quantitatively study the effects of the two types of perfusion. The MRA images were used to reconstruct an individual three-dimensional (3D) model of cerebral arteries. The pulsatile blood flow measured by Trans-Cranial Doppler ultrasonic-graph (TCD) was applied as boundary conditions for CFD simulations. Result: Hemodynamic parameters in the 3D cerebral vascular model were compared among the patients with the existence or absence Circle of Willis at the condition of the unilateral and bilateral antegrade selective cerebral perfusion. Pressure and mass flow are maintained both under unilateral perfusion and bilateral perfusion unless the wills ring is incomplete. Conclusion: For some patients with cerebral artery stenosis, the unilateral cerebral perfusion will cause brain injury.

We evaluated the effects of different respiratory assist modes on cerebral blood flow (CBF) and arterial oxygenation in single-ventricle patients after bidirectional superior cavopulmonary anastomosis (BCPA). We hypothesized that preserved auto-regulation of respiration during neurally adjusted ventilatory assist (NAVA) may have potential advantages for CBF and pulmonary blood flow regulation after the BCPA procedure. We enrolled 23 patients scheduled for BCPA, who underwent pressure-controlled ventilation (PCV), pressure support ventilation (PSV), and NAVA at two assist levels for all modes in a randomized order. PCV targeting large V T (15 mL × kg−1) resulted in lower CBF and oxygenation compared to targeting low V T (10 mL × kg−1). During PSV and NAVA, ventilation assist levels were titrated to reduce EAdi from baseline by 75 % (high assist) and 50 % (low assist). High assist levels during PSV (PSVhigh) were associated with lower PaCO2, PaO2, and O2SAT, lower CBF, and higher pulsatility index compared with those during NAVAhigh. There were no differences in parameters when using low assist levels, except for slightly greater oxygenation in the NAVAlow group. Modifying assist levels during NAVA did not influence hemodynamics, cerebral perfusion, or gas exchange. Targeting the larger V T during PCV resulted in hyperventilation, did not improve oxygenation, and was accompanied by reduced CBF. Similarly, high assist levels during PSV led to mild hyperventilation, resulting in reduced CBF. NAVA’s results were independent of the assist level chosen, causing normalized PaCO2, improved oxygenation, and better CBF than did any other mode, with the exception of PSV at low assist levels.

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.

This study evaluated the performance of a centrifugal blood pump designed for the children with heart failure. In this work, to better understand the hemodynamic effects of LVAD outflow-graft anastomosis location, a 3D blood pump model is constructed and patient-specific of ventricular volume is considered. The aim of the research is to observe the impact of the physiological waveform, the periodic ventricular volume signal as import boundary conditions. The distribution of pressure, streamlines and wall shear stress of the blades were calculated under all of the continuous period. The hemolysis of the pump was predicted. The result of computational fluid dynamics under unsteady state shows that the Centrifugal Blood Pump for the Children with Cardiac Failure is running stability under a Physiological waveform import, and pressure of the outlet of the pump is fit the periodic demand.

Pulmonary artery banding (PAB) is a commonly used palliative procedure to restrict excess pulmonary blood in certain congenital heart diseases. However, many associated long-term hemodynamic problems still remain unsolved over the years. In this study, we utilized the method of computational fluid dynamics (CFD) to investigate the hemodynamic effects of PAB on patient-specific pulmonary flow before, 1 year and 2 years after banding. The distribution of total pressure, wall shear stress, streamlines and energy efficiency were calculated. The results indicated a sharp pressure drop at the banding site. Energy efficiency loss decreased greatly as the loosening of PAB, and strong whirling flow was observed in the dilated MPA after banding. The method of CFD can be used to disclose the hemodynamics of PAB.

For the purpose of supporting the in-vitro circulation of the children with cardiac failure, a centrifugal blood pump is under development in our hospital, currently. We design a suspended impeller with a single supporting point bearing to provide a blood flow. Towards the end of efficient design, the techniques of computer-aided design (CAD) and computational fluid dynamics (CFD) are employed for the development and quantitative evaluation of the fluid dynamic performance. In this study, we report the process of the design and CFD estimation of the dynamic characteristics of a prototype. The three-dimensional flow features inside of the pump were predicted. An unobstructed blood flow path without secondary flow and stagnated flow regions was achieved. The pressure-flow curves, hydraulic efficiencies and wall shear stress (WSS) of the blades were calculated. The results indicated the design of the impeller was good enough to generate a relatively efficient flow patterns in the blade passage to reduce the flow separation and formation of vortices which are believed to increase the degree of hemolysis and thrombosis. In addition, the flow through the hydrodynamic bearing at the center of the impeller and the effects of bearing clearance on shear stress were also investigated for the further optimization of the pump design and the improvement of the hemolytic performance. This implied the analysis of CFD simulation were the efficient tool in the evaluation of the blood pump design.

Objective To investigate the effect of afterload pressure on hemolytic blood damage in centrifugal pump.Methods The differences between velocity,pressure and surface shear force of the internal flow of Sarns2000 centrifugal pump with afterload pressure and those without afterload pressure were obtained by computational fluid dynamics(CFD).Results The velocity and flow of pump deceased when the rotational speed was 1 400 r/min with afterload pressure.The hemolytic blood damage increased with the pressure increase in the pump.However,the area whose surface shear force was greater than 150 Pa was less than 0.000032%,which had a good performance of hemolysis.Conclusion The afterload pressure would enhance the possibility of hemolysis in Sarns2000 centrifugal pump,while the surface shear force has a good performance of hemolysis.