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      Vascular Hemodynamics: Deep-Rooted Misconceptions and Misnomers

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          Abstract

          Erroneous concepts about vascular hemodynamics are widespread, notably as regards the effect of gravity on blood flow. Vascular pressure at any point is equal to the sum of two pressures of entirely different origins: (1) pressure caused by the pumping action of the heart (‘cardiodynamic’ pressure which is vital for circulation) and (2) pressure due to gravity acting on the blood (‘gravitational’ or hydrostatic pressure which plays no direct role in blood flow). Gravity neither helps nor hinders circulation because of the U tube or siphon principle. The gravitational energy of the column of blood in arteries is balanced exactly by the gravitational energy of the column in veins and vice versa. Thus, contrary to common belief, gravity does not hinder blood flow to the head in the upright position, nor does it hinder venous return from the dependent parts of the body. For this reason, in Poiseuille’s equation, perfusion pressure should exclude gravitational pressure. Postural effects on circulation result from the distension of vessels (particulary veins) subsequent to changes in gravitational pressure of blood.

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          Author and article information

          Journal
          CRD
          Cardiology
          10.1159/issn.0008-6312
          Cardiology
          S. Karger AG
          0008-6312
          1421-9751
          1979
          1979
          31 October 2008
          : 64
          : 4
          : 197-207
          Affiliations
          Department of Physiology, Creighton University School of Medicine, Omaha, Nebr.
          Article
          170616 Cardiology 1979;64:197–207
          10.1159/000170616
          476727
          © 1979 S. Karger AG, Basel

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          Page count
          Pages: 11
          Categories
          Original Paper

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