Sedimentation Kinetics of Concentrated Red Blood Cell Suspensions in a Centrifugal Field: Determination of Aggregation and Deformation of RBC by Flux Density and Viscosity Functions
The flow properties of blood are usually
determined using various viscometric approaches, and described in terms of a
shear rate or shear stress dependent apparent viscosity. The
interpretation of such results are rather difficult, especially at low shear
rates when particle sedimentation and migration within the viscometer gap are
significant. By contrast, analyzing the separation process in concentrated
RBC suspensions in a centrifugal field yields information about the viscosity
function in addition to particle–particle interactions such as coagulation,
aggregation and deformation. In this paper, the sedimentation kinetics of
rigid spherical RBC suspended in saline and normal RBC suspended in Dx-saline
solutions were investigated by means of the LUMiFuge separation analyzer.
The data obtained with sedimentation of rigid spherical RBC at different volume
concentrations demonstrate that, in the case of suspensions rotated in
containers of constant cross section, there is good agreement between the theory
of kinematic waves developed by Anestis and Schneider (1983) and the results of
the experiments. Excellent agreement was obtained even though a
restrictive one-dimensional model was used to obtain the theoretically derived
sedimentation time course. In addition, we describe an algorithm enabling the
experimental determination of the viscosity and related flux density function to
be made for any suspension. Through this approach, we investigated in
detail the rheological behavior of suspended rigid spheres at low Reynolds
numbers ranging from 10-6
to 10-3. The method here introduced also enabled us to investigate RBC suspensions with
respect to the deformability and interactions of the cells by means of the
separation analysis. Normal, rigid as well as aggregating RBC exhibited
marked differences in the sedimentation kinetics, which were quantified by means
of the flux and viscosity functions based on the theory of kinematic waves.
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