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Research Papers

Design Optimization of a Wearable Artificial Pump-Lung Device With Computational Modeling

[+] Author and Article Information
M. Ertan Taskin, Tao Zhang, Katharine H. Fraser, Bartley P. Griffith

 Artificial Organs Laboratory, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201

Zhongjun J. Wu1

 Artificial Organs Laboratory, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201zwu@smail.umaryland.edu

1

Corresponding author. Department of Surgery, University of Maryland School of Medicine, MSTF-436, 10. S. Pine Street, Baltimore, MD 21201.

J. Med. Devices 6(3), 031009 (Aug 20, 2012) (12 pages) doi:10.1115/1.4007282 History: Received December 14, 2011; Revised May 17, 2012; Published August 20, 2012; Online August 20, 2012

The heart-lung machine has commonly been used to replace the functions of both the heart and lungs during open heart surgeries or implemented as extracorporeal membrane oxygenation (ECMO) to provide cardiopulmonary support of the heart and lungs. The traditional heart-lung system consists of multiple components and is bulky. It can only be used for relatively short-term support. The concept of the wearable artificial pump-lung is to combine the functions of the blood pumping and gas transfer in a single, compact unit for cardiopulmonary or respiratory support for patients suffering from cardiac failure or respiratory failure, or both, and to allow patients to be ambulatory. To this end, a wearable artificial lung (APL) device is being developed by integrating a magnetically levitated centrifugal impeller with a hollow fiber membrane bundle. In this study, we utilized a computational fluid dynamics based performance optimization with a heuristic scheme to derive geometrical design parameters for the wearable APL device. The configuration and dimensions of the impeller and the diffuser, the required surface area of fiber membranes and the overall geometrical dimensions of the blood flow path of the APL device were considered. The design optimization was iterated based on the fluid dynamic objective parameters (pressure head, pressure distribution, axial force acting on the impeller, shear stress), blood damage potential (hemolysis and platelet activation), and mass transfer (oxygen partial pressure and saturation). Through the design optimization, an optimized APL device was computationally derived. A physical prototype of the designed APL device was fabricated and tested in vitro. The experimental data showed that the optimized APL can provide adequate blood pumping and oxygen transfer over the range of intended operating conditions.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The concept of a wearable artificial pump lung in an ambulatory patient

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Figure 2

Conceptualization of the flow path and components for the APL

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Figure 3

(a) The design parameters based on the variation of shroud structure (group 1) and the impeller height (group 2). (b) The design parameters based on the variation of number of blades (group 3), discharge angle (group 4), and number of diffuser fins (group 5). (c) The design parameters based the fiber bundle dimensions (group 6).

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Figure 4

CFD based design optimization strategy

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Figure 5

Calculated pressure head values for groups 1 and 2 (above), and for groups 3, 4, and 5 (below) at 7000 rpm and 3.5 L/min

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Figure 6

Pressure distribution of models 01-04 on the central cut plane at 7000 rpm and 3.5 L/min

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Figure 7

Mean shear stresses calculated in the rotating domain for groups 1 and 2 (above), and for groups 3, 4, and 5 (below) at 7000 rpm and 3.5 L/min

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Figure 8

Calculated hemolysis indexes at the exit of the device model for groups 1 and 2 (above), and for groups 3, 4, and 5 (below) at 7000 rpm and 3.5 L/min

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Figure 9

Hemolysis index distribution of models 01-04 on the central cut plane at 7000 rpm and 3.5 L/min

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Figure 10

The shear stress distribution (left) and vectors-colored with HI- (right) on the central cut plane for group 2 variable at 7000 rpm and 3.5 L/min. The images from top to bottom are for models 03, 03-b, and 03-c, respectively.

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Figure 11

Calculated platelet activation functions for groups 1 and 2 (above), and for groups 3, 4, 5 (below) at 7000 rpm and 3.5 L/min

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Figure 12

Oxygen transfer rates (above) and saturations (below) at 7000 rpm and 3.5 L/min

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Figure 13

Shear stress contours on a interface side surface for models in group 4 at 7000 rpm and 3.5 L/min

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Figure 14

Velocity vector fields on the middle-blade cut plane. A representative section is shown for 7000 rpm and 3.5 L/min.

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Figure 15

Computationally predicted and measured performance data of the final APL design for flow rates up to 5.5 L/min at the rotational speeds of 6000, 7000, and 8000 rpm

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