Time-dependent rheological behaviour of blood flow at low shear in narrow horizontal tubes

Issue title: Stanley Mason Memorial Issue

Guest editors: Harry L. Goldsmith

Article type: Research Article

Authors: Alonso, C. | Pries, A.R. | Gaehtgens, P.

Affiliations: Institut für Physiologie, Freie Universität Berlin, Arnimallee 22, D-1000 Berlin 33, FRG

Abstract: Magnitude and time-dependence of the effects of red cell aggregation and sedimentation on the rheology of human blood were studied during low shear (τW 2.5 to 92 mPa) flow through horizontal tubes (ID 25 to 105 μm). Immediately following reduction of perfusion pressure to a low value the red cell concentration near the tube walls decreases as a result of red cell aggregation. This is associated with a transient increase of centerline velocity. Simultaneously, sedimentation begins to occur and eventually leads to the formation of a cell-free supernatant plasma layer. Time-course and extent of this sedimentation process are strongly affected by wall shear stress variation, particularly in the larger tubes. At the lower shear stresses, centerline velocity decreases (flow resistance increases) with time following the initial acceleration period, due to sedimentation of red cells. This is followed by a further increase of resistance caused by the elevation of hematocrit occurring because of the reduction of cell/plasma velocity ratio. The time dependence of blood rheological behaviour under these flow conditions is interpreted to reflect the net effect of the partially counteracting phenomena of sedimentation and red cell aggregation.

Keywords: sedimentation, red cell aggregation, blood rheology, horizontal tube, low shear flow, plasma layer

DOI: 10.3233/BIR-1989-26210

Journal: Biorheology, vol. 26, no. 2, pp. 229-246, 1989