Rotary Blood Pumps Research Articles

Impact of extracorporeal blood pump gap sizes on the performance and hemocompatibility under off-design operation.

Hemocompatibility remains the dominant challenge in rotary blood pumps, and more information on the relationship between individual pump design features, hemodynamics, and blood trauma in various operation conditions is necessary. The study evaluated the variation of gap sizes in extracorporeal blood pumps concerning their influence on blood compatibility, particularly during off-design conditions. We developed a parametric generic blood pump framework for in-silico and in-vitro design feature analysis. Thirty-six designs with varying axial and radial gap sizes between 0.5 mm and 3 mm were generated. CFD was applied to calculate and compare device hemodynamics and evaluate the performance and hemocompatibility during off-design and target operation conditions. The following quantities were analyzed: pressure difference, hemolysis potential, residence times, hydraulic efficiency, and recirculation ratio. The in-vitro prototype showed excellent agreement with in-silico predictions regarding hydraulic performance (R2 = 0.996 with a RMSE = 2.07). Our results show a modest impact of gap size variations ±10% on key metrics. Domain-resolved analyses revealed a significant contribution of the gap regions to the device's overall hemolytic performance, with an increasing contribution for off-design flow rates. Overall elevated hemolysis levels were identified if at least one gap size was held minimal. We introduced and showed the feasibility of a parametric rotary blood pump framework to systematically investigate design feature impact. Results suggest, larger and uniformly sized gaps being overall beneficial regarding hemocompatibility.

Validating the Concept of Mechanical Circulatory Support with a Rotary Blood Pump in the Inferior Vena Cava in an Ovine Fontan Model.

Right-sided mechanical support of the Fontan circulation by existing devices has been compounded by the cross-sectional design of vena cava anastomosis to both pulmonary arteries. Our purpose was to investigate whether increasing inferior vena cava (IVC) flow with a rotary blood pump in the IVC only in an ovine animal model of Fontan would lead to acceptable superior vena cava (SVC) pressure. To achieve this, a Fontan circulation was established in four female sheep by anastomosing the SVC to the main pulmonary artery (MPA) and by interposing a Dacron graft between the IVC and the MPA. A rotary blood pump was then introduced in the graft, and the effect of incremental flows was observed at increasing flow regimen. Additionally, to stimulate increased pulmonary resistance, the experience was repeated in each animal with the placement of a restrictive band on the MPA distally to the SVC and Dacron graft anastomosis. Circulatory support of IVC flow alone increased the systemic cardiac output significantly, both with and without banding, indicating the feasibility of mechanical support of the Fontan circulation by increasing the flow only in the inferior vena cava. The increase in SVC pressure remained within acceptable limits, indicating the potential effectiveness of this mode of support. The findings suggest that increasing the flow only in the inferior vena cava is a feasible method for mechanical support of the Fontan circulation, potentially leading to an increase in cardiac output with acceptable increases in superior vena cava pressure.

Practical Comparison of Two- and Three-Phase Bearingless Permanent Magnet Slice Motors for Blood Pumps

The majority of bearingless permanent magnet slice motors (BPMSMs) used in commercially available rotary blood pumps use a two-phase configuration, but it is unclear as to whether or not a comparable three-phase configuration would offer a better performance. This study compares the performance of two-phase and three-phase BPMSM configurations. Initially, two nominal designs were manufactured and empirically tested for their performance characteristics, namely, the axial stiffness, radial stiffness, and current force. Subsequently, finite element analysis (FEA) models were developed based on these nominal devices and validated against the empirical results. Simulations were then employed to assess the sensitivity of performance characteristics to variations in seven different geometric features of the models for both configurations. Our findings indicate that the nominal three-phase design had a higher axial stiffness and radial stiffness, but resulted in a lower axial-to-radial-stiffness ratio when compared to the nominal two-phase design. Additionally, while the nominal two-phase design shows a higher current force, the nominal three-phase design proves to be slightly superior when the force generated is considered relative to the power usage. Notably, the three-phase configuration demonstrates a greater sensitivity to dimensional changes in the geometric features. We observed that alterations in the air gap and rotor length lead to the most significant variations in performance characteristics. Although most changes in specific geometric features entail equal tradeoffs, increasing the head protrusion positively influences the overall performance. Moreover, we illustrated the interdependent nature of the head height and rotor height on the performance characteristics. Overall, this study delineates the strengths and weaknesses of each configuration, while also providing general insights into the relationship between specific geometric features and performance characteristics of BPMSMs.

Toward an Adjustable Blood Pump for Wide-Range Operation: In-Vitro Results of Performance Curve and Hydraulic Efficiency.

Rotary blood pumps in Extracorporeal Life Support (ECLS) applications are optimized for a specific design point. However, in clinical practice, these pumps are usually applied over a wide range of operation points. Studies have shown that a deviation from the design point in a rotary blood pump leads to an unexpected rise of hemolysis with corresponding clinical complications. Adjustable pumps that can adapt geometric parameters to the respective operation point are commonly used in other industrial branches, but yet not applied in blood pumps. We present a novel mechanism to adjust the impeller geometry of a centrifugal blood pump during operation together with in-vitro data of its hydraulic performance and efficiency. Three-dimensionalprinted prototypes of the adjustable impeller and a rigid impeller were manufactured and hydraulic performance and efficiency measured (n = 3). In a flow range of 1.5-9.5 L/min, the adjustable pump increased pump performance up to 47% and hydraulic efficiency by an average of 7.3 percentage points compared with a fixed setting. The adjustable pump allows customization of the pump's behavior (steepness of performance curve) according to individual needs. Furthermore, the hydraulic efficiency of the pump could be maintained at a high level throughout the complete flow range.

Novel closed-loop control system of dual rotary blood pumps in total artificial heart based on the circulatory equilibrium framework: a proof-of-concept in vivo study.

Total artificial heart (TAH) using dual rotary blood pumps (RBPs) is a potential treatment for end-stage heart failure. A well-noted challenge with RBPs is their low sensitivity to preload, which can lead to venous congestion and ventricular suction. To address this issue, we have developed an innovative closed-loop control system of dual RBPs in TAH. This system emulates the Frank-Starling law of the heart in controlling RBPs while monitoring stressed blood volume (V) based on the circulatory equilibrium framework. We validated the system in in-vivo experiments. In 9 anesthetized dogs, we prepared a TAH circuit using 2 centrifugal-type RBPs. We first investigated whether the flow and inlet atrial pressure in each RBP adhered to a logarithmic Frank-Starling curve. We then examined whether the RBP flows and atrial pressures were maintained stably during aortic occlusion (AO) and pulmonary cannula stenosis (PS), whether averaged flow of dual RBPs and bilateral atrial pressures were controlled to their predefined target values for a specific V, and whether this system could maintain the atrial pressures within predefined control ranges under significant changes in V. This system effectively emulated the logarithmic Frank-Starling curve. It robustly stabilized the flow and atrial pressures during AO and PS without venous congestion or ventricular suction, accurately achieved target values in averaged flow and atrial pressures, and efficaciously maintained these pressures within the control ranges. This system controls dual RBPs in TAH accurately and stably. This system may accelerate clinical application of TAH with dual RBPs.

Study on the hemodynamic effects of different pulsatile working modes of a rotary blood pump using a microfluidic platform that realizes in vitro cell culture effectively.

Rotary blood pumps (RBPs) operating at a constant speed generate non-physiologic blood pressure and flow rate, which can cause endothelial dysfunction, leading to adverse clinical events in peripheral blood vessels and other organs. Notably, pulsatile working modes of the RBP can increase vascular pulsatility to improve arterial endothelial function. However, the laws and related mechanisms of differentially regulating arterial endothelial function under different pulsatile working modes are still unclear. This knowledge gap hinders the optimal selection of the RBP working modes. To address these issues, this study developed a multi-element in vitro endothelial cell culture system (ECCS), which could realize in vitro cell culture effectively and accurately reproduce blood pressure, shear stress, and circumferential strain in the arterial endothelial microenvironment. Performance of this proposed ECCS was validated with numerical simulation and flow experiments. Subsequently, this study investigated the effects of four different pulsation frequency modes that change once every 1-4-fold cardiac cycles (80, 40, 80/3, and 20 cycles per min, respectively) of the RBP on the expression of nitric oxide (NO) and reactive oxygen species (ROS) in endothelial cells. Results indicated that the 2-fold and 3-fold cardiac cycles significantly increased the production of NO and prevented the excessive generation of ROS, potentially minimizing the occurrence of endothelial dysfunction and related adverse events during the RBP support, and were consistent with animal study findings. In general, this study may provide a scientific basis for the optimal selection of the RBP working modes and potential treatment options for heart failure.

Efficacy assessment of strategies for mechanical univentricular circulatory support

Univentricular palliation is performed in patients with congenital heart defects, such as single functional ventricle, hypoplasia, septal defects, valve defects, obstructive defects, etc. After the palliation, the single ventricle becomes systemic, and venae cavae are directly or indirectly connected to pulmonary arteries. Palliated patients may temporary lead a full life yet eventually need heart transplantation. Mechanical circulatory support (MCS) may be an alternative treatment for heart transplantation in patients having univentricular circulation. Personalized modeling of a biotechnical MCS system allows to forecast current and optimal system states and assess support advisability and efficacy before implanting a circulatory assist device. In this study, a mathematical model of univentricular circulation with possibility to connect a circulatory assist device is presented. An algorithm for efficacy forecast and assessment of personalized mechanical univenricular circulatory support was developed. The algorithm automatically determines circulatory model parameters based on patient’s hemodynamic data and a set of parameter templates for corresponding age groups and circulatory states. This first stage is based on genetic algorithm with model parameters used as a genotype. Criterion of obtaining personalized model parameters is a zero sum of relative deviations of patient’s hemodynamic data and simulated data after personalization given the acceptable ranges of deviations determined based on accuracy of clinical diagnostic devices. At the second stage, the developed algorithm simulates a personalized biotechnical system of mechanical univentricular circulatory support using personalized circulatory model and pressure head–flow rate characteristics of circulatory assist device. At the third stage, the algorithm assesses advisability of chosen control strategy with negative recommendation for inadvisable strategy. At the last stage, the algorithm forecasts optimal states of biotechnical system determined as sufficiently approximate to normal circulation. Verification of the developed algorithm was performed with patients’ hemodynamic data from literature. Distributions of hemodynamic parameters in simulated biotechnical systems for three patients are described along with forecast optimal states and corresponding values of control parameter for chosen methods of support. In these cases, pediatric rotary blood pump previously developed by our research group was used as circulatory assist device. Assessment of changes in biotechnical system after implantation of circulatory assist device revealed inefficacy of MCS in one of three considered patients.

Spiral groove bearing design for improving plasma skimming in rotary blood pumps

High-efficiency plasma skimming is hopeful to prevent hemolysis inside spiral groove bearings (SGBs) because it can exclude red blood cells from the ridge gap with a high shear force. However, no study reveals the shape design of SGBs to improve plasma skimming. Therefore, this study proposed and applied a groove design strategy to designing an optimal SGB for enhancing plasma skimming in a rotary blood pump (RBP). Initially, we proposed the design strategy that the shape of the groove for enhancing plasma skimming corresponds to the direction of blood flow in the ridge gap. Second, we visualized the cell flow in a specially designed experimental RBP to determine the direction of blood flow, which was helpful in the subsequent SGB design. Then, we created an SGB to provide superior plasma skimming and applied it to the experimental RBP. We evaluated the plasma skimming effect of SGB at rotational speeds ranging from 2400 to 3000 rpm and hematocrit conditions between 1% and 40%. At a 1% hematocrit, the plasma skimming efficiency for the entire SGB was greater than 95%. In all hematocrit conditions, the efficiency at the inner ridges of the SGB was greater than 80%. The results showed the designed SGB successfully induced excellent plasma skimming within ridge gaps. This study is the first to propose and apply a shape design strategy to generate excellent plasma skimming within an SGB. This study may contribute to the prevention of SGB hemolysis inside SGB for use in RBPs.

Systematic analysis of non-intrusive polynomial chaos expansion to determine rotary blood pump performance over the entire operating range

This study applies non-intrusive polynomial chaos expansion (NIPCE) surrogate modeling to analyze the performance of a rotary blood pump (RBP) across its operating range. We systematically investigate key parameters, including polynomial order, training data points, and data smoothness, while comparing them to test data. Using a polynomial order of 4 and a minimum of 20 training points, we successfully train a NIPCE model that accurately predicts pressure head and axial force within the specified operating point range ([0–5000] rpm and [0–7] l/min). We also assess the NIPCE model's ability to predict two-dimensional velocity data across the given range and find good overall agreement (mean absolute error = 0.1 m/s) with a test simulation under the same operating condition. Our approach extends current NIPCE modeling of RBPs by considering the entire operating range and providing validation guidelines. While acknowledging computational benefits, we emphasize the challenge of modeling discontinuous data and its relevance to clinically realistic operating points. We offer open access to our raw data and Python code, promoting reproducibility and accessibility within the scientific community. In conclusion, this study advances comprehensive NIPCE modeling of RBP performance and underlines how critically NIPCE parameters and rigorous validation affect results.

Abstract 16713: Pre-Clinical 30-day Survival Results of the BiVACOR TAH

Introduction: The BiVACOR Total Artificial Heart (TAH) replaces the failing heart with a durable and physiologically adaptive pump, which combines magnetic levitation and rotary blood pump technology. The pump has large clearances to minimize shear stress, generates pulse pressure via cyclic changes in pump speed, and modulates total outflow based on physiological conditions. A single rotor design enables a small pump size. Aim: Primary endpoint was survival at 30 days with normal end-organ function and absence of device related thromboembolism at necropsy. Methods: Five calves (82 - 108 kg) were implanted with the BiVACOR TAH and underwent continuous hemodynamic monitoring for 30 days. The pumps ability to generate a pulse pressure, balance outflow to the systemic and pulmonary circulations and to increase outflow in response to increased physical activity was assessed. Hemocompatibility and end-organ function were routinely monitored. Necropsy was performed on day 30 to evaluate for evidence of thromboembolism and end organ damage. Explanted pumps were examined. Results: All five calves survived to 30 days with normal end-organ function. Stable hemodynamics were achieved with normal pressures in the aorta and left and right atrium (MAP 111 ± 6 mmHg, CVP 12 ± 5 mmHg, LAP of 20 +/- 5 mmHg). Average estimated pump output was 12 ± 2 L/min with average pulse pressure of 30 mmHg. Pump output increased during changes in daily physiological condition (10 to 14 L/min). No device-related thromboembolism or other end organ pathologies were detected at necropsy. All explanted pumps were free of internal pump thrombus. Hemocompatibility was demonstrated (pfHb 4.34 ± 0.74 mg/dL). Bypass time decreased by 34 minutes over the entire study cohort. Conclusion: The BiVACOR TAH demonstrates normal hemodynamics including left/right balance. Pump design allows for a normal pulse pressure, increased pump output in response to exercise, and excellent hemocompatibility without device-related thromboembolism. Operative time markedly improves with surgeon experience. The small pump size may expand the use of TAH to smaller patients. This device may address the need for select patients with advanced heart failure who require biventricular support.

Dissipated energy and efficiency as objective functions for the design of the NeoVAD rotary blood pump.

Minimising haemolytic blood damage is an important objective when designing rotary blood pumps, however, calculating haemolysis can be computationally expensive and inaccurate. Efficiency and dissipated energy are much more easily calculable hydraulic parameters in the design and analysis of rotary blood pumps and although there is work to suggest that efficiency is not a good indicator of haemocompatibility, i.e. more efficient pumps do not necessarily cause less damage, there is recent speculation that dissipated energy can act as an easily calculable haemolysis analogue.This study shows that for design purposes, optimising for maximum efficiency and minimum dissipated energy are functionally the same as they are inherently and closely linked. Moreover a demonstration of rotary blood pump design has been completed using the NeoVAD paediatric left ventricular assist device optimising for both objective functions. The resulting designs appear similar in rotor blade shape and are similar in hydraulic performance.Clinical relevance- This reinforces the direct link between efficiency and dissipated energy when analysing rotary blood pumps at a given design operating point. This raises questions either of the claim that efficiency cannot be used as an easily calculable analogue for haemolysis or the validity of dissipated energy to act in this same manner.

Circulatory Support: Artificial Muscles for the Future of Cardiovascular Assist Devices.

Artificial muscles enable the design of soft implantable devices which are poised to transform the way wemechanically support the heart today. Heart failure is a prevalent and deadly disease, which is treated with the implantation of rotary blood pumps as the only alternative to heart transplantation. The clinically used mechanical devices are associated with severe adverse events, which are reflected here in a comprehensive list of critical requirements for soft active devices of the future: low power, no blood contact, pulsatile support, physiological responsiveness, high cycle life, and less-invasive implantation. In this review, prior art in artificial muscles for their applicability in the short and long term is investigated and critically evaluated. The main challenges regarding the effectiveness, controllability, and implantability of recently proposed actuators are highlighted and the future perspectives for attachment, physiological responsiveness, durability, and biodegradability as well as equitable design considerations are explored.

Accelerated Hemocompatibility Testing of Rotary Blood Pumps.

Ex vivo hemocompatibility testing is a vital element of preclinical assessment for blood-contacting medical devices. Current approaches are resource intensive; thus, we investigated the feasibility of accelerating hemocompatibility testing by standardizing the number of pump exposures in loops of various sizes. Three identical blood loops were constructed, each with a custom-molded reservoir able to facilitate large-volume expansion. Using the HVAD rotary blood pump operating at 5 L·min-1 and 100 mmHg, three test volumes (80, 160, and 320 ml) were circulated for 4000 pump exposures. Blood sampling was performed at individualized intervals every one-sixth of total duration for the assessment of hemolysis and von Willebrand Factor (vWF) degradation. While steady increases in hemolysis (~24 mg·dl-1) were identified in all tests at completion, loop volume was not a primary discriminator. The normalized index of hemolysis did not vary significantly between loops (4.2-4.9 mg·100 L-1). vWF degradation progressively occurred with duration of testing to a similar extent under all conditions. These data support an accelerated approach to preclinical assessment of ex vivo blood damage. Adopting this approach enables: enhanced efficiency for rapid prototyping; reduced ex vivo blood aging, and; greater utility of blood, which is presently limited if 450 ml loops are desired.

CARD5: Chronic In-vivo evaluation of the BiVACOR rotary total artificial heart

Purpose: The BiVACOR Total Artificial Heart (TAH) combines magnetic levitation and rotary blood pump technology to create a small, durable and physiologically compatible device capable of replacing the failing heart. Pulsatile outflow is achieved via cyclic changes in pump speed, while large clearance gaps and flow paths improve hemocompatibility. The TAH is designed for implantation in women and some children, yet powerful enough to support adult males undergoing exercise. In preparation for first-in-human trials, in-vivo studies were undertaken using clinical-grade devices. Methods: The BiVACOR TAH was implanted into five calves (82 – 108 kg) for 30 days before elective termination. Hemodynamics, left-right balance, hemocompatibility, and end organ function were monitored throughout the study, while evidence of significant thromboembolism was evaluated at study termination via necropsy. Results: All five calves regained all physiological function (eating, drinking, defecating, standing, and regular treadmill exercise). The TAH demonstrated reliable operation, provided suitable hemodynamics (MAP 111 ± 6 mmHg, CVP 12 ± 5 mmHg, est.QL 12 ± 1 l/min) with pulsatile outflow (up to 40 mmHg @ 60BPM) and acceptable left/right balance (est.LAP-CVP 7.6 ± 3 mmHg). Normal end organ function was maintained (CREA 1 ± 0.44 mg/dL) with excellent hemocompatibility (pfHb 4.34 ± 0.74 mg/dL, LDH 1110 ± 182 U/L), while showing no evidence of significant device related thrombi or end organ dysfunction at necropsy. Summary: The BiVACOR TAH demonstrated promising chronic physiological performance, hemocompatibility, and physiological interaction. These results underpin progression of the BiVACOR TAH to first-in-human studies. The work was supported by NIH NHLBI under award number R44HL137454.

A novel model for hemolysis estimation in rotating impeller blood pumps considering red blood cell aging.

For blood pumps with a rotating vane-structure, hemolysis values are estimated using a stress-based power-law model. It has been reported that this method does not consider the red blood cell (RBC) membrane's shear resistance, leading to inaccurate estimation of the hemolysis value. The focus of this study was to propose a novel hemolysis model which can more accurately predict the hemolysis value when designing the axial flow blood pump. The movement behavior of a single RBC in the shear flow field was simulated at the mesoscale. The critical value of shear stress for physiological injury of RBCs was determined. According to the critical value, the equivalent treatment of RBC aging was studied. A novel hemolysis model was established considering the RBC's aging and the hemolysis' initial value. The model's validity was verified under the experimental conditions of shear stress loading and the conditions of the shear flow field of the blood pump. The results showed that compared with other hemolysis models for estimating the hemolysis value of blood pumps, the novel hemolysis model proposed in this paper could effectively reduce the estimation error of the hemolysis value and provide a reference for the optimal design of rotary vane blood pumps.

Hemodynamic investigation of a novel rotary displacement blood pump for extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is a life support system used in the treatment of severe respiratory and circulatory failure. High shear stress caused by the high rotational speed of centrifugal blood pumps can cause hemolysis and platelet activation, which are among the major factors leading to the complications of the ECMO system. In this study, a novel blood pump named rotary displacement blood pump (RDBP), which can considerably reduce rotational speed and shear stress while ensuring the normal pressure flow relationship, was proposed. We employed computational fluid dynamics (CFD) analysis to investigate the performance of RDBP under adult ECMO support operating conditions (5 L/min with 350 mmHg). The efficiency and H-Q curves of the RDBP were calculated to evaluate its hydraulic performance, and pressure, flow patterns, and shear stress distribution were analyzed to estimate the hemodynamic characteristics in the pump. In addition, the modified index of hemolysis (MIH) was calculated for the RDBP based on a Eulerian approach. The hydraulic efficiency of the RDBP was 47.28%. The velocity distribution of flow field in the pump was relatively uniform. Most of the liquid (more than 75%) in the pump was exposed to low scale shear stress (<1 Pa), which was close to normal physiological conditions. The gap area was the main distribution location of high scale shear stress. The high wall shear stress (>9 Pa) volume fraction of the RDBP was small and located in the boundary areas between the rotor's edge and the housing. The MIH value of the RDBP was 9.87 ± 0.93 (mean ± SD). The RDBP can achieve better hydraulic efficiency and hemodynamic performance at lower rotational speed. The design of this novel pump is expected to provide a new direction for developing a blood pump for ECMO.

The Evolution of Durable, Implantable Axial-Flow Rotary Blood Pumps

Left ventricular assist devices (LVADs) are increasingly used to treat patients with end-stage heart failure. Implantable LVADs were initially developed in the 1960s and 1970s. Because of technological constraints, early LVADs had limited durability (eg, membrane or valve failure) and poor biocompatibility (eg, driveline infections and high rates of hemolysis caused by high shear rates). As the technology has improved over the past 50 years, contemporary rotary LVADs have become smaller, more durable, and less likely to result in infection. A better understanding of hemodynamics and end-organ perfusion also has driven research into the enhanced functionality of rotary LVADs. This paper reviews from a historical perspective some of the most influential axial-flow rotary blood pumps to date, from benchtop conception to clinical implementation. The history of mechanical circulatory support devices includes improvements related to the mechanical, anatomical, and physiologic aspects of these devices. In addition, areas for further improvement are discussed, as are important future directions-such as the development of miniature and partial-support LVADs, which are less invasive because of their compact size. The ongoing development and optimization of these pumps may increase long-term LVAD use and promote early intervention in the treatment of patients with heart failure.

A comparative study of structural parameters for spiral groove bearing in centrifugal rotary blood pump

In this work, the hydrodynamic characteristics of spiral groove bearing in centrifugal rotary blood pump is investigated for the cases with different structural parameters. The simulation model is proposed based on the CFD technology and the effectiveness of simulation model is demonstrated by the published data. Then, the pressure, load carrying capacity and friction torque are calculated and the characteristics of pressure distribution are analyzed. It is found that the structural parameters of spiral groove would lead to the complex pressure distribution of blood film and the load carrying capacity also changes at the same time. Moreover, the deep analysis of structural characteristics for spiral groove bearing is conducted based on the orthogonal design method, which could improve the computational efficiency of hydrodynamic behavior of spiral groove bearing. And, the mapping relationship between structural parameter and hydrodynamic performance of bearing preferably is also illustrated.

A sensorless, physiologic feedback control strategy to increase vascular pulsatility for rotary blood pumps

Continuous flow rotary blood pumps (RBP) operating clinically at constant rotational speeds cannot match cardiac demand during varying physical activities, are susceptible to suction, diminish vascular pulsatility, and have an increased risk of adverse events. A sensorless, physiologic feedback control strategy for RBP was developed to mitigate these limitations. The proposed algorithm used intrinsic pump speed to obtain differential pump speed (ΔRPM). The proposed gain-scheduled proportional-integral controller, switching of setpoints between a higher pump speed differential setpoint (ΔRPMHr) and a lower pump speed differential setpoint (ΔRPMLr), generated pulsatility and physiologic perfusion, while avoiding suction. The switching between ΔRPMHr and ΔRPMLr setpoints occurred when the measured ΔRPM reached the pump differential reference setpoint. In-silico tests were implemented to assess the proposed algorithm during rest, exercise, a rapid 3-fold pulmonary vascular resistance increase, rapid change from exercise to rest, and compared with maintaining a constant pump speed setpoint. The proposed control algorithm augmented aortic pressure pulsatility to over 35 mmHg during rest and around 30 mmHg during exercise. Significantly, ventricular suction was avoided, and adequate cardiac output was maintained under all simulated conditions. The performance of the sensorless algorithm using estimation was similar to the performance of sensor-based method. This study demonstrated that augmentation of vascular pulsatility was feasible while avoiding ventricular suction and providing physiological pump outflows. Augmentation of vascular pulsatility can minimize adverse events that have been associated with diminished pulsatility. Mock circulation and animal studies would be conducted to validate these results.

Numerical hemolysis performance evaluation of a rotary blood pump under different speed modulation profiles.

Introduction: Speed modulation methods have been studied and even used clinically to create extra pulsation in the blood circulatory system with the assistance of a continuous flow rotary blood pump. However, fast speed variations may also increase the hemolysis potential inside the pump. Methods: This study investigates the hemolysis performance of a ventricular assist rotary blood pump under sinusoidal, square, and triangular wave speed modulation profiles using the computational fluid dynamics (CFD) method. The CFD boundary pressure conditions of the blood pump were obtained by combining simulations with the pump's mathematical model and a complete cardiovascular lumped parameter model. The hemolysis performance of the blood pump was quantified by the hemolysis index (HI) calculated from a Eulerian scalar transport equation. Results: The HI results were obtained and compared with a constant speed condition when the blood pump was run under three speed profiles. The speed modulations were revealed to slightly affect the pump hemolysis, and the hemolysis differences between the different speed modulation profiles were insignificant. Discussion: This study suggests that speed modulations could be a feasible way to improve the flow pulsatility of rotary blood pumps while not increasing the hemolysis performance.