Rheological properties of blood as assessed with a newly designed oscillating viscometer

Article type: Research Article

Authors: Reinhart, W.H. | Häusler, K. | Schaller, P. | Erhart, S. | Stetter, M. | Dual, J. | Sayir, M.

Affiliations: Internal Medicine, Kantonsspital, CH 7000 Chur, Switzerland | Institute of Mechanics, ETH Zürich, CH 8092 Zürich, Switzerland

Abstract: A newly designed type of oscillating viscometer was tested for blood viscosity measurements. The viscometer consists of a probe (either a tube or a rod) oscillating at a resonance frequency with amplitudes in the micro‐ and nanometer range. The torsional oscillations are dampened by fluids flowing through the tube or surrounding the rod. The degree of damping depends on the viscosity of the fluid, which allows to measure viscosity. Data obtained with these instruments were compared with those obtained with a conventional Couette viscometer. An increase of erythrocyte aggregation by the addition of dextran 70 in vitro led to the expected increase of viscosity in the Couette viscometer; in the oscillating tube viscometer, however, it remained unchanged, which may be explained by a decreased erythrocyte concentration near the tube wall due to increased aggregation and flow of erythrocytes in the tube center. In ex vivo experiments on blood flowing without anticoagulant directly through the tube viscometer an inverse correlation between viscosity and fibrinogen concentration was found. This is in contrast to actual knowledge and may indicate that high fibrinogen levels have a beneficial rheological effect at the tube or vessel wall. Our data suggest that the new oscillating tube viscometer is an interesting tool, which may contribute to a more comprehensive understanding of blood flow.

Keywords: Aggregation, blood, erythrocyte, fibrinogen, viscosity

Journal: Clinical Hemorheology and Microcirculation, vol. 18, no. 1, pp. 59-65, 1998