Structure and hemodynamics of microvascular networks: heterogeneity
and correlations.
Pries, A. R., T. W. Secomb, and P. Gaehtgens.
Dept. of Physiology, Freie Universit[umlaut]at Berlin, Arnimallee
22, D-14195 Berlin, Germany, Dept. of Physiology, University of
Arizona, Tucson, AZ 85724, USA
APStracts 2:0254H, 1995.
The objective of this study was to quantify the heterogeneity of
topological, morphological and hemodynamic parameters in
microvascular networks, and to identify functionally relevant
correlations among these parameters. Seven networks in the rat
mesentery (383 to 913 vessel segments per network) were examined, and
measurements were made of segment generation, diameter, length, and
hematocrit in all segments (n = 3129) and of flow velocity (only in 3
networks, 1321 segments). In addition, hematocrit, flow rate and
pressure were derived for all segments from a mathematical
simulation. All parameters obtained exhibit heterogeneous
distributions with coefficients of variation ranging from 0.28
(capillary diameter) to above 1.5 (volume flow and pressure
gradient). Several strong correlations exist between parameters,
e.g., discharge hematocrit increases with vessel diameter, and shear
rate increases with intravascular pressure. Due to such correlations,
the extrapolation from average values for 'typical vessels' to
network properties can lead to substantial errors. For example, the
mean network transit time estimated based on averaged quantities, is
6.5 s, which is about 60% higher than the true value (4.08 s).
Simplified models of the vascular bed may therefore be inadequate to
describe functional properties of the microcirculation.
Received 21 February 1995; accepted in final form 9 June 1995.
APS Manuscript Number H160-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.