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Hemodynamic impact and thickness of the endothelial surface layer in microvascular networks
Author(s) -
Pries Axel R,
Secomb Timothy W.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a281
Subject(s) - hematocrit , hemodynamics , microcirculation , blood flow , flow velocity , biomedical engineering , materials science , flow (mathematics) , chemistry , mechanics , physics , medicine , cardiology
The presence of a layer on the endothelial surface (ESL) with thickness of ~0.4 to over 1 μm that retards flow of plasma and cellular components of blood is now generally accepted. Its effect on flow resistance has been demonstrated by infusion of enzymes to digest carbohydrates of the glycocalyx. An alternative approach to assess its hemodynamic impact is to compare measured flow velocity distributions in microvascular networks with corresponding mathematical simulations under different assumptions on layer thickness. This was done here using morphological and flow velocity data obtained by intravital microscopy for three complete networks in the rat mesentery with 392, 546 and 383 vessel segments. Flow distribution was simulated assuming diameter‐dependent rheological properties of blood as determined in vitro and the presence of an ESL with a high hydraulic resistance. The dependence of the effective ESL thickness on vessel diameter was varied to minimize the deviation of estimated velocities from measured values (>velocity error=). A substantial reduction of velocity error was found if a thickness of ~0.8 μm at vessel diameters of 10 μm, declining to ~0.1–0.2 μm for the smallest capillaries, was assumed. Introducing an additional hematocrit‐dependent impact on flow resistance with a maximum for diameters around 10 μm led to a further reduction of the velocity error. The results show that the hemodynamic effect of the ESL depends on both vessel diameter and hematocrit and is larger than would be predicted based on methods to visualize the layer. Supported by NIH grant HL34555.