Two-port analysis of the microcirculation: an extension of the
windkessel.
Frasch, H. Frederick, J. Yasha Kresh, and Abraham Noordergraaf.
Center for Anesthesia Research and Department of Bioengineering,
University of Pennsylvania, Philadelphia, PA 19104, Department of
Cardiothoracic Surgery, Likoff Cardiovascular Institute, Hahnemann
University, Philadelphia, PA 19102
APStracts 2:0307H, 1995.
We examine the suitability of the 3-element Windkessel as a reduced
model of pulsatile pressure/flow relations at arteriolar and venular
ends of a microcirculatory bed. Frequency domain (2-port) analysis of
a distributed model of an idealized (single input, single output)
microvascular network in skeletal muscle, consisting of 391 discrete
vessel segments from a 20 [mu]m diameter arteriole to 28 [mu]m
venule, demonstrates that the 3-element Windkessel is a good
representation of arterial input impedance when pressure pulsations
are absent at the venous end. The same model with different parameter
values accounts well for venous pressure/flow relations if no
pulsations occur at the arterial end. We show that a 5-element model
(2 compliances, 3 resistors) provides a superior representation of
pulsatile pressure/flow relations at both arterial and venous ends.
Relating parameter values to known properties of the network reveals
the physiological significance of the 5 elements. This model may
prove a useful component in circulatory models incorporating both
arteries and veins. While parameter values obtained herein are
strictly valid for the particular microvascular network described,
guidelines are provided based on physiological properties so that
values may be estimated for different microvascular beds.
Received 8 June 1994; accepted in final form 28 June 1995.
APS Manuscript Number H505-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.