The arterial system P-V loop
C. M. Quick, David S. Berger, and A. Noordergraaf
XIV Congress, Cardiovascular System DynamicsSociety, Baltimore, MD, 2000
Abstract
Although the ventricular P-V loop has become a popular tool to characterize
the heart, an arterial system P-V loop has not yet been described. This
is because, unlike flow into the arterial system, Qin,
flow out of it, Qout, cannot be measured directly.
Recently, we have shown that Qout can be adequately approximated
by P/Rtot, where P is root aortic pressure and Rtot is total
peripheral resistance (Ann Biomed Eng 28: 291-301, 2000). The
volume stored in the arterial system, V, can then be calculated by
integrating the difference between Qin and Qout
. Illustrated below is the systemic arterial system P-V loop of a dog
calculated from measured P and Qin. This new
characterization can be recognized as an alternative implementation of the
traditional Windkessel concept. According to the Windkessel concept,
the arterial system can be characterized as a chamber that stores blood.
Recently, the classical Windkessel model has been generalized with the concept
of apparent arterial compliance, Capp, which is the transfer
function V(w)/P(w) expressed in the frequency
domain (Am J Physiol 274: H1393-H1403, 1998). The arterial system
P-V loop is a time-domain representation of Capp. Hopefully, this representation will make the difficult concept of
apparent compliance more accessible as a tool to characterize the arterial
system.
