Viscosity of the Blood in Narrow Capillary Tubes

Fahraeus and Lindqvist (1931) documents an experimental investigation involving the different viscosities of blood flowing through capillary tubes of different diameter. The authors measured apparent relative blood viscosityi.e., relative to the viscosities measured for waterand showed that they depend on the size of the capillary tube through which the blood is flowing. This research is significant in that it reveals a relationship previously overlooked by other investigators (Fahraeus & Lindqvist, 1931). Through keen observation, Fahraeus and Lindqvist proved that as tube diameters decrease, so too does apparent relative viscosity (Fahraeus & Lindqvist, 1931). Thus, this work represents an important advance in the understanding of hemodynamics which may have widespread implications for the study of human physiology.

In light of previous work done in this area, the relationship outlined by Fahraeus and Lindqvist in regard to blood viscosities comes rather unexpectedly (Fahraeus & Lindqvist, 1931, pp. 562563). Research performed by the French physician, Poiseuille, on the problem of bloodstream resistance in the narrow parts of the vascular system produced different results entirely (Fahraeus & Lindqvist, 1931, p. 562). Unable to use genuine blood, Poiseuille conducted his tests using water and other fluids (Fahraeus & Lindqvist, 1931, p. 562). He found that the time of efflux for a g

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d Lindqvist precluded these difficulties by creating an innovative apparatus which employed rotary motion to maintain blood homogeneity (Fahraeus & Lindvquist, 1931, pp. 563564). The authors provide a description and an illustration of this viscosimeter (Fahraeus & Lindvquist, 1931, pp. 563564). They neglect, however, to mention how 100 mm. Hg pressures were achieved or how temperatures were held constant in their "thermostate". Furthermore, the excessive wordiness of their description makes for difficult visualization of the device. The paper needs a more detailed illustration of Fahraeus and Lindqvist's new invention. In regard to the results and discussion, however, the data and their analysis seem adequate. Appropriately enough, Fahraeus and Lindqvist used several tables to present their viscosities (Fahraeus & Lindqvist, 1931, p. 565). Also, they provided sufficient elucidation of the methods by which blood specimens of varying plasma viscosities were obtained (Fahraeus & Lindqvist, 1931, pp. 564565). Furthermore, as was called for, they performed control analyses using water and derived experimental values that corresponded well with those that were to be expected (Fahraeus & Lindqvist, 1931, p. 565). The
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Approximate Pages = 6 (250 words per page)