Fluid Dynamic Characterization of Operating Conditions for Continuous Flow Blood Pumps

Wu, Zhongjun J.; Antaki, James F.; Burgreen, Greg W.; Butler, Kenneth C.; Thomas, D.; Griffith, Bartley P.

doi:10.1097/00002480-199909000-00015

Cited by 43 publications

(30 citation statements)

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“…These experiments are not intended as a substitute for formal verification and validation, but as a supplementary tool to gain insight to the internal hemodynamics as influenced by flow rate and pulsatility. This study employed flow visualization techniques reported previously 19, 31–33 that provide only a qualitative assessment of the flow fields. Although more sophisticated and quantitative methods are available, we found that a great deal of insight was provided by direct observation of the tracer pathlines.…”

Section: Discussionmentioning

confidence: 99%

“…However the results reported here may be translated to a wide range of conditions through the use of non-dimensional analysis. For steady state flow, Wu et al 31 illustrated that the number of independent variables may be reduced to two

pressure coefficient : normalΨ = \frac{normalg normalH}{R^{2} Ω^{2}}

and flow coefficient : normalΦ = \frac{Q}{normalA normalR normalΩ}

where H and Q are the pressure head and flow rate respectively, R is the radius of the pump impeller, A is the flow discharge area, Ω is the rotational speed of the impeller and g is the acceleration due to gravity. Not only does this simplify the experimental matrix, but also the extrapolation of these results to other combinations of flow rate, pressure head, and speed.…”

Section: Discussionmentioning

confidence: 99%

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High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

Yang

Kormos

Antaki

2015

The Journal of Thoracic and Cardiovascular Surgery

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Objective: To investigate potentially pro-thrombotic flow patterns within an axial flow ventricular assist device under clinically relevant pulsatile hemodynamic conditions. Methods A transparent replica of the HeartMate-II was visualized using a high speed camera at both low and high frame rates (125 and 3000 fps). Three steady-state conditions were studied: nominal (4.5 lpm), low flow (3.0 lpm) and high flow (6.0 lpm). Time-varying conditions were introduced with external pulsatile pump which modulated the flow rate by approximately +/−50% of the mean, corresponding to a pulsatility index of 1.0. Results At nominal and high flow rates, the path lines within the upstream region were generally stable, well attached, and streamlined. As the flow rate was reduced below 3.8 lpm, a rapid transition to a chaotic velocity field occurred exhibiting a large toroidal vortex adjacent to the upstream bearing. The pathlines in the downstream stator section were consistently chaotic for all hemodynamic conditions investigated. It was common to observe tracer particles trapped within recirculation bubbles and drawn retrograde, causing repeated contact with the bearing surfaces. The addition of pulsatility caused the flow field to become periodically chaotic during the diastolic portion of the cardiac cycle depending on the instantaneous flow rate and acceleration. Conclusion The contribution of pulsatility by the native heart may induce a periodic disturbance to an otherwise stable flow field within an axial flow VAD, particularly during the diastolic and decelerating portion of the cardiac cycle. Potentially pro-thrombotic flow features were found to occur periodically in the region of the upstream bearing.

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Section: Discussionmentioning

confidence: 99%

pressure coefficient : normalΨ = \frac{normalg normalH}{R^{2} Ω^{2}}

and flow coefficient : normalΦ = \frac{Q}{normalA normalR normalΩ}

Section: Discussionmentioning

confidence: 99%

High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

Yang

Kormos

Antaki

2015

The Journal of Thoracic and Cardiovascular Surgery

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“…Therefore computational fluid dynamics was used to both calibrate the mean line formulae, and to optimize the unspecified features of the blood flow path. The procedure, described previously18,19,74-76 utilized a commercial CFD program (CFX 11, ANSYS, Inc., Canonsburg, PA, USA) employing both k – ε and SST turbulent models, that is coupled to an external optimization algorithm (see Fig. 8).…”

Section: Methodsmentioning

confidence: 99%

PediaFlow™ Maglev Ventricular Assist Device: A Prescriptive Design Approach

Antaki

Ricci

Verkaik

et al. 2010

Cardiovasc Eng Tech

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This report describes a multi-disciplinary program to develop a pediatric blood pump, motivated by the critical need to treat infants and young children with congenital and acquired heart diseases. The unique challenges of this patient population require a device with exceptional biocompatibility, miniaturized for implantation up to 6 months. This program implemented a collaborative, prescriptive design process, whereby mathematical models of the governing physics were coupled with numerical optimization to achieve a favorable compromise among several competing design objectives. Computational simulations of fluid dynamics, electromagnetics, and rotordynamics were performed in two stages: first using reduced-order formulations to permit rapid optimization of the key design parameters; followed by rigorous CFD and FEA simulations for calibration, validation, and detailed optimization. Over 20 design configurations were initially considered, leading to three pump topologies, judged on the basis of a multi-component analysis including criteria for anatomic fit, performance, biocompatibility, reliability, and manufacturability. This led to fabrication of a mixedflow magnetically levitated pump, the PF3, having a displaced volume of 16.6 cc, approximating the size of a AA battery and producing a flow capacity of 0.3-1.5 L/min. Initial in vivo evaluation demonstrated excellent hemocompatibility after 72 days of implantation in an ovine. In summary, combination of prescriptive and heuristic design principles have proven effective in developing a miniature magnetically levitated blood pump with excellent performance and biocompatibility, suitable for integration into chronic circulatory support system for infants and young children; aiming for a clinical trial within 3 years.

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“…10,11,25,27 Computational Fluid Dynamics (CFD) is a relatively quick method for predicting a steady flow field; however it is much more challenging to simulate unsteady conditions, 22 and in some cases prohibitive. Additional limitations and uncertainties associated with CFD, such as simulating turbulent conditions, prompt the use of experimental validation.…”

Section: Introductionmentioning

confidence: 99%

Classification of Unsteady Flow Patterns in a Rotodynamic Blood Pump: Introduction of Non-Dimensional Regime Map

Shu

Vandenberghe

Brackett

et al. 2015

Cardiovasc Eng Tech

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Rotodynamic blood pumps (also known as rotary or continuous flow blood pumps) are commonly evaluated in vitro under steady flow conditions. However, when these devices are used clinically as ventricular assist devices (VADs), the flow is pulsatile due to the contribution of the native heart. This study investigated the influence of this unsteady flow upon the internal hemodynamics of a centrifugal blood pump. The flow field within the median axial plane of the flow path was visualized with particle image velocimetry (PIV) using a transparent replica of the Levacor VAD. The replica was inserted in a dynamic cardiovascular simulator that synchronized the image acquisition to the cardiac cycle. As compared to steady flow, pulsatile conditions produced periodic, transient recirculation regions within the impeller and separation in the outlet diffuser. Dimensional analysis revealed that the flow characteristics could be uniquely described by the non-dimensional flow coefficient (Φ) and its time derivative ([Formula: see text]), thereby eliminating impeller speed from the experimental matrix. Four regimes within the Φ-[Formula: see text] plane were found to classify the flow patterns, well-attached or disturbed. These results and methods can be generalized to provide insights for both design and operation of rotodynamic blood pumps for safety and efficacy.

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Fluid Dynamic Characterization of Operating Conditions for Continuous Flow Blood Pumps

Cited by 43 publications

References 0 publications

High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

High-speed visualization of disturbed pathlines in axial flow ventricular assist device under pulsatile conditions

PediaFlow™ Maglev Ventricular Assist Device: A Prescriptive Design Approach

Classification of Unsteady Flow Patterns in a Rotodynamic Blood Pump: Introduction of Non-Dimensional Regime Map

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