Computational Characterization of Flow and Hemolytic Performance of the UltraMag Blood Pump for Circulatory Support

Journal of Biomechanical Engineering

Taşkın

et al. 2012

Self Cite

299

378

Ventricular assist devices (VADs) have already helped many patients with heart failure but have the potential to assist more patients if current problems with blood damage (hemolysis, platelet activation, thrombosis and emboli, and destruction of the von Willebrand factor (vWf)) can be eliminated. A step towards this goal is better understanding of the relationships between shear stress, exposure time, and blood damage and, from there, the development of numerical models for the different types of blood damage to enable the design of improved VADs. In this study, computational fluid dynamics (CFD) was used to calculate the hemodynamics in three clinical VADs and two investigational VADs and the shear stress, residence time, and hemolysis were investigated. A new scalar transport model for hemolysis was developed. The results were compared with in vitro measurements of the pressure head in each VAD and the hemolysis index in two VADs. A comparative analysis of the blood damage related fluid dynamic parameters and hemolysis index was performed among the VADs. Compared to the centrifugal VADs, the axial VADs had: higher mean scalar shear stress (sss); a wider range of sss, with larger maxima and larger percentage volumes at both low and high sss; and longer residence times at very high sss. The hemolysis predictions were in agreement with the experiments and showed that the axial VADs had a higher hemolysis index. The increased hemolysis in axial VADs compared to centrifugal VADs is a direct result of their higher shear stresses and longer residence times. Since platelet activation and destruction of the vWf also require high shear stresses, the flow conditions inside axial VADs are likely to result in more of these types of blood damage compared with centrifugal VADs.

Section: Methodsmentioning

confidence: 99%

“…[32,33,34]). There are a number of studies using CFD to investigate localized shear stress in different regions of VADs, particularly for design analysis or improvement [35][36][37][38][39]. However, there are fewer studies in which the authors have analyzed the whole VAD to obtain the volumetric parameters.…”

Section: Introductionmentioning

confidence: 99%

A Quantitative Comparison of Mechanical Blood Damage Parameters in Rotary Ventricular Assist Devices: Shear Stress, Exposure Time and Hemolysis Index

Fraser

Journal of Biomechanical Engineering

Taşkın

et al. 2012

Self Cite

299

378

“…To meet the above requirements, a very small magnetic levitation/motor system, currently used for the UltraMag® blood pump (Levitronix, LLC, Waltham, MA, USA) 10 , was selected to drive the magnetically levitated impeller and a similar flow configuration was adopted from the previously developed bed-side IMPO 8, 9 . The impeller, diffuser, and flow path from the inlet to outlet, all blood contacting surfaces and surface area of the hollow fiber membranes (HFM) were optimized for pumping function, oxygen transfer and biocompatibility using computational fluid dynamics (CFD) based modeling and design analysis 11 .…”

Section: Methodsmentioning

confidence: 99%

A novel wearable pump-lung device: In vitro and acute in vivo study

The Journal of Heart and Lung Transplantation

Wei

Bianchi

et al. 2012

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Background To provide long-term ambulatory cardiopulmonary and respiratory support for adult patients, a novel wearable artificial pump-lung device has been developed. The design features, in-vitro and acute in-vivo performance of this device are reported in this paper. Methods This device features a uniquely designed hollow fiber membrane bundle integrated with a magnetically levitated impeller together to form one ultra-compact pump-lung device, which can be placed like current paracorporeal ventricular assist devices to allow ambulatory support. The device is 117 mm in length and 89 mm in diameter and has a priming volume of 115 ml. In-vitro hydrodynamic, gas transfer and biocompatibility experiments were carried out in mock flow loops using ovine blood. Acute in-vivo characterization was conducted in ovine by surgically implanting the device between right atrium and pulmonary artery. Results The in-vitro results showed that the device with a membrane surface area of 0.8 m2 was capable of pumping blood from 1 to 4 L/min against a wide range of pressures and transferring oxygen at a rate of up to 180 ml/min at a blood flow of 3.5 L/min. Standard hemolysis tests demonstrated low hemolysis at the targeted operating condition. The acute in-vivo results also confirmed that the device can provide sufficient oxygen transfer with excellent biocompatibility. Conclusions Base on the in-vitro and acute in-vivo study, this highly integrated wearable pump-lung device can provide efficient respiratory support with good biocompatibility and it is ready for long-term evaluation.

“…The hemolytic blood damage potential was calculated by Eulerian approach, in which the hemolysis index was predicted by solving a scalar transport equation [11]. The scalar quantity and the source term were derived from the power-law equation to determine flow induced hemolysis from shear stress level and exposure time.…”

Section: Numerical and Experimental Methodsmentioning

confidence: 99%

Computational Fluid Dynamics and Experimental Characterization of the Pediatric Pump-Lung

Gellman

et al. 2011

Cardiovasc Eng Tech

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The pediatric pump-lung (PediPL) is a miniaturized integrated pediatric pump-oxygenator specifically designed for cardiac or cardiopulmonary support for patients weighing 5-20 kg to allow mobility and extended use for 30 days. The PediPL incorporates a magnetically levitated impeller with uniquely configured hollow fiber membranes into a single unit capable of performing both pumping and gas exchange. A combined computational and experimental study was conducted to characterize the functional and hemocompatibility performances of this newly developed device. The three-dimensional flow features of the PediPL and its hemolytic characteristics were analyzed using computational fluid dynamics based modeling. The oxygen exchange was modeled based on a convection-diffusion-reaction process. The hollow fiber membranes were modeled as a porous medium which incorporates the flow resistance in the bundle by an added momentum sink term. The pumping function was evaluated for the required range of operating conditions (0.5-2.5 L/min and 1000-3000 rpm). The blood damage potentials were further analyzed in terms of flow and shear stress fields, and the calculations of hemolysis index. In parallel, the hydraulic pump performance, oxygen transfer and hemolysis level were quantified experimentally. Based on the computational and experimental results, the PediPL device is found to be functional to provide necessary oxygen transfer and blood pumping requirements for the pediatric patients. Smooth blood flow characteristics and low blood damage potential were observed in the entire device. The in-vitro tests further confirmed that the PediPL can provide adequate blood pumping and oxygen transfer over the range of intended operating conditions with acceptable hemolytic performance. The rated flow rate for oxygenation is 2.5 L/ min. The normalized index of hemolysis is 0.065 g/100L at 1.0 L/min and 3000 rpm. Keywordspediatric circulatory support; pediatric cardiopulmonary assist device; pump-oxygenator; computational fluid dynamics; in vitro characterization Address correspondence and reprint requests to Zhongjun