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RESEARCH PAPERS

Hot-Film Wall Shear Probe Measurements Inside a Ventricular Assist Device

[+] Author and Article Information
J. T. Baldwin, D. B. Geselowitz

Bioengineering Program, The Pennsylvania State University, University Park, Pa. 16802

J. M. Tarbell

Department of Chemical Engineering, The Pennsylvania State University, University Park, Pa. 16802

S. Deutsch

Applied Research Laboratory, The Pennsylvania State University, University Park, Pa. 16802

G. Rosenberg

Division of Artificial Organs, Department of Surgery, The Pennsylvania Park University, Hershey, Pa. 17033

J Biomech Eng 110(4), 326-333 (Nov 01, 1988) (8 pages) doi:10.1115/1.3108449 History: Received October 17, 1987; Revised September 02, 1988; Online June 12, 2009

Abstract

Wall shear rates at eleven sites within the Penn State Electric Ventricular Assist Device (EVAD) were determined with the pump operating under conditions of 30 and 50 percent systolic duration and a mean flow rate of 5.8 L/min using a flush-mounted hot-film probe. Probe calibrations were performed with the hot-film in two orientations relative to the flow direction: a standard orientation and an orientation in which the hot-film was rotated by 90 deg from the standard orientation. The magnitude and direction of the wall shear stress at each site within the EVAD were estimated from ensemble averaged voltage data recorded for similar standard and rotated film orientations. The results indicate that, during diastole the wall shear stress direction around the pump’s periphery for both operating conditions is predominantly perpendicular to the inflow-outflow plane (in the direction of the pusher plate motion) and reaches a peak value of approximately 350 dynes/cm2 . The highest wall shear stresses were found near the prosthetic aortic valve (inside the EVAD) under the 30 percent systolic duration condition and are estimated to be as high as 2700 dynes/cm2 . Peak shear stress values of 1400 dynes/cm2 were observed in the vicinity of the prosthetic mitral valve under both operating conditions. The results suggested that the valve regions are substantially more hemolytic than other wall regions of the EVAD; the magnitudes of the wall shear stresses are sensitive to operating conditions; and that wall shear in the direction of pusher plate motion can be significant.

Copyright © 1988 by ASME
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