AJP - Heart and Circulatory Physiology, Vol 271, Issue 5 1807-H1813, Copyright © 1996 by American Physiological Society
Method for determining distribution of reflection sites in the arterial system
F. Pythoud, N. Stergiopulos, N. Westerhof and J. J. Meister
Biomedical Engineering Laboratory, Swiss Federal Institute of Technology, PSE-Ecublens, Lausanne, Switzerland.
We developed a new method to determine the location and importance of
reflection sites in the arterial system. The method is based on the
decomposition of the aortic pressure wave into its forward and backward
components, and it provides the reflection profile of the arterial system
as a wave reflection site amplitude versus distance from the heart. The
reflection profile can be seen as the response of the arterial system to a
pressure delta pulse where reflections upstream from the measurement
location have been eliminated. The method was successfully tested on a
simple model loaded with a pure resistor, a two-element windkessel, and a
bifurcating tube system. It was then applied to the aortic pressure and
flow signals measured in six mongrel dogs whose aorta was occluded at
different levels. The profiles obtained from measurements at control showed
two main reflection regions, one located in the vicinity (0.1-0.2 m) of the
heart and the other located in the region of the iliac bifurcation. All
occlusions, even the most distant one at the iliac bifurcation, could be
identified in both amplitude (amount of reflections) and distance from the
heart. The spatial resolution of the profiles was approximately 0.1 m as a
result of the limited power spectrum contained in the arterial pulse, and
the identification of reflection sites decreased rapidly with the distance.
