Flow visualization with blood analog fluid

A Flow Visualization Study of Prosthetic Aortic and Mitral Heart Valves in a Model of the Aorta and Left Heart

An in vitro flow visualization study has been carried out on a range of aortic and mitral valve prostheses mounted in rigid, transparent models of the aorta and left ventricle, The valves were subjected to pulsatile flow and the flow patterns produced by each valve were visualized by injecting multi-dye streams into the valve orifice, or by observing illuminated particles suspended in the flow. The patterns were recorded by still photography and high speed cinematography.

In the mitral region each tilting disc valve produced a large vortex which dominated the ventricular cavity. By contrast disc and ball valves each produced an annular vortex, and the bioprosthesis produced a central flow. In the aortic region the flow patterns produced by a tilting disc valve depended on the orientation of the valve in the aorta. The aortic ball valve was found to produce less flow disturbance than either tilting disc valve or the porcine bioprosthesis.

Design engineering of a bioartificial renal tubule cell therapy device

The use of a bioartificial renal tubule device composed of renal proximal tubule cells grown within a hollow fiber cartridge is a first step in engineering a bioartificial kidney to provide more complete replacement therapy of renal function than is available today. In this study, the feasibility of two designs for a tubule device were investigated: one with cells grown on microcarrier beads densely packed within the extracapillary space of a hollow fiber cartridge, and the other with cells grown as a confluent monolayer within the hollow fibers themselves. First, the oxygen requirements of porcine renal proximal tubule cells were determined, both attached to microcarriers and in suspension and compared to that of proximal tubule segments. The basal rate of cell respiration was found to be 2.29 +/- 0.53 nmol O2/10(6) cells/min for our cultured proximal tubule cells in suspension and no significant difference was seen with attached cells. Proximal tubule segments displayed significantly higher respiratory rates. Cells were also found to be responsive in the presence of mitochondrial inhibitors or uncouplers, and their respiratory rates remained constant, despite multiple passaging. The resultant cell oxygen consumption parameter was used in models describing oxygen concentration profiles within the two device configurations. From these models, it was found that cells within our proposed device designs could theoretically be sustained and remain viable, with respect to oxygen limitations. Finally, flow visualization studies were performed to assess fluid flow distribution and determine optimal device configuration and geometry to decrease areas of low or stagnant flow.