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Research Papers

Particle-Image Velocimetry Study of a Pediatric Ventricular Assist Device

[+] Author and Article Information
E. Ferrara1

Optics Group, Physics Institute, University of São Paulo, São Paulo, SP Brazileferrara@if.usp.br

M. Muramatsu

Optics Group, Physics Institute, University of São Paulo, São Paulo, SP Brazil

K. T. Christensen

Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL

I. A. Cestari

Department of Bioengineering, Heart Institute, InCor, University of São Paulo Medical School, SP, Brazil

1

Corresponding author.

J Biomech Eng 132(7), 071004 (May 18, 2010) (6 pages) doi:10.1115/1.4001252 History: Received August 28, 2009; Revised January 22, 2010; Posted February 11, 2010; Published May 18, 2010; Online May 18, 2010

Abstract

Particle-image velocimetry (PIV) was used to visualize the flow within an optically transparent pediatric ventricular assist device (PVAD) under development in our laboratory. The device studied is a diaphragm type pulsatile pump with an ejection volume of 30 ml per beating cycle intended for temporary cardiac assistance as a bridge to transplantation or recovery in children. Of particular interest was the identification of flow patterns, including regions of stagnation and/or strong turbulence that often promote thrombus formation and hemolysis, which can degrade the usefulness of such devices. For this purpose, phase-locked PIV measurements were performed in planes parallel to the diaphram that drives the flow in the device. The test fluid was seeded with $10 μm$ polystyrene spheres, and the motion of these particles was used to determine the instantaneous flow velocity distribution in the illumination plane. These measurements revealed that flow velocities up to 1.0 m/s can occur within the PVAD. Phase-averaged velocity fields revealed the fixed vortices that drive the bulk flow within the device, though significant cycle-to-cycle variability was also quite apparent in the instantaneous velocity distributions, most notably during the filling phase. This cycle-to-cycle variability can generate strong turbulence that may contribute to greater hemolysis. Stagnation regions have also been observed between the input and output branches of the prototype, which can increase the likelihood of thrombus formation.

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Figures

Figure 1

Prototype of the PVAD under study. The blood chamber and bovine pericardial valves, which are used in the inflow and outflow branches, are shown. The drive line of the pneumatic pressure actuator is also apparent.

Figure 2

Photo of the experimental setup showing the positions of the fluid chamber of the PVAD traversed by the light sheet through the window of the dark chamber for image acquisition. The insert drawing shows the three light-sheet orientations studied relative to the diaphram motion plane.

Figure 3

Phase-average velocity fields within the ejection phase of the PVAD operating at 80 bpm in plane 2 at (a) Ta=0 ms and (b) Ta=150 ms

Figure 4

Phase-average velocity fields within the ejection phase of the PVAD operating at 80 bpm in plane 2 at (a) Ta=250 ms and (b) Ta=450 ms

Figure 5

Phase-average velocity fields within the filing phase of the PVAD operating at 80 bpm in plane 2 at (a) Ta=550 ms and (b) Ta=650 ms

Figure 6

Phase-average velocity fields for consecutive phases in the filling phase operating at 80 bpm in plane 1 at (a) Ta=525 ms and (b) Ta=550 ms

Figure 7

Phase-average velocity field in the filling phase operating at 80 bpm in plane 1 at Ta=575 ms

Figure 8

Phase-average velocity fields in plane 3 at Ta=300 ms for frequencies of (a) 80 bpm and (b) 100 bpm

Figure 9

(a) Representative instantaneous velocity field and (b) phase-average velocity field in plane 1 for a frequency of 80 bpm at Ta=550 ms

Figure 10

Contour map of the turbulent shear stress τR=−ρ⟨u′v′⟩ corresponding to the case presented in Fig. 9 (plane 1 at 80 bpm and Ta=550 ms)

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