Role of arterial design on pulse wave reflection in a fractal
pulmonary network.
Bennett, Stephen H., Boyd W. Goetzman, Jay M. Milstein, Jatinder S.
Pannu.
DIVISION OF NEONATOLOGY, DEPARTMENT OF PEDIATRICS, UNIVERSITY OF
CALIFORNIA, DAVIS, DAVIS, CA 95616
APStracts 2:0482A, 1995.
A novel interpretation of pulmonary arterial input impedance was
evaluated for the lung as a fractal vascular network. We hypothesized
that local sources of reflection introduce trends of global
reflection into the input impedance spectra. These trends are related
to the network topology, geometry and design according to Rb=Rd^x,
where Rb is the branching ratio, Rd is the diameter ratio, and x is
the fractal dimension quantifying design. Simulations using values of
Rd and x, which were derived morphometrically, confirmed two patterns
of global reflection: a continuous trend attributed to a single
effective site of reflection caused by frequency dependent sources of
impedance contrast; and a discrete trend arising from a longitudinal
distribution of frequency independent sources of reflection. The
continuous trend depended only on the network parameter Rd while the
discrete trend depended on both Rd and x. Our results indicate that
the impedance matching properties of a deterministic pulmonary
fractal network encode arterial geometry and topology via function,
and that typical values of Rd and x for the pulmonary circulation
facilitate shear-stress amplification in its peripheral vessels.
Thus, as shear forces may be involved in the endothelial mechanisms
for pathological, or physiological, vascular remodeling, broadband
input impedance analysis may reveal interactions between network
organization and vascular function.
Received 3 February 1995; accepted in final form 26 October 1995.
APS Manuscript Number A132-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95