Fåhræus–Lindqvist effect
Fluid dynamics phenomenon in blood
The Fåhræus–Lindqvist effect ( far-AY-əs LIND-kvist) or sigma effect describes how the viscosity of blood changes with the diameter of the vessel it travels through. In particular there is a decrease in viscosity as the vessel diameter decreases, but only at small diameters of 10–300 micrometers (mainly capillaries). This is because erythrocytes move to the centre of the vessel, leaving only plasma near the wall of the vessel.
History
The effect was first documented by a German group in 1930. Shortly after, in 1931, it was reported independently by the Swedish scientists Robin Fåhræus (1888–1968) and Johan Torsten Lindqvist (1906–2007), after whom the effect is commonly named. Fåhræus was a pathologist and hematologist, Lindqvist was a physician. Fåhræus and Lindqvist published their article in the American Journal of Physiology in 1931 describing the effect. Their study represented an important advance in the understanding of hemodynamics which had widespread implications for the study of human physiology.
They forced blood through fine glass capillary tubes connecting two reservoirs. Capillary diameters were less than 250 μm, and experiments were conducted at sufficiently high shear rates (≥100 1/s) so that a similar flow in a large tube would be effectively Newtonian.
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This entry incorporates text from “Fåhræus–Lindqvist effect” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.