8
Dynamics
of
the Vascular System
1.3
Modern
Concepts
Modern development of the theory related to blood flow in the vascular
system has included multi-faceted aspects, such
as,
fluid mechanics,
fluid-vessel
interface,
vascular
tissue
engineering,
pulse
wave
transmission and mathematical modeling.
The mathematical formulations of blood flow through visoelastic
arteries have been well established and documented in many texts (e.g.
Noordergraaf,
1978;
Li,
1987;
Nichols and O’Rourke,
1998;
Li,
2000).
These texts also provided experimental measurement methods and
quantitative approaches to the assessments of the state of the arterial
circulation.
There
are
also
several
texts
in
describing
the
microcirculation (e.g. Lee and Skalak,
1989;
Fung,
1997)
In the application to clinical situations, the interpretation of the
morphology of blood pressure and flow waveforms in relation to
underlying diseased conditions has attracted the most attention. The
introduction of new groups of drugs beyond vasodilators, beta adrenergic
blockers, calcium channel blockers and angiotensin-converting enzyme
inhibitors that includes local targeted vascular drug delivery,
as
well the
beginning stages of gene therapy, to improve vascular perfusion and in
the treatment of diseases, have become more avant garde.
Not only the arteries, the microcirculatory vessels are no longer
viewed as resistance
vessels, but are compliant with
viscoelastic
properties that vary with frequency. The classical elastic description of
blood vessels has been modified to include viscosity of the blood and the
vessel wall. The viscosity causes energy dissipation. Thus, the energy
utilization and dissipation in relation to blood flow
is
now considered
pertinent. Regarding Chi, or energy, the amount of the work that the
heart has to generate during each beat has generated considerable
attention. This included the steady energy dissipation through peripheral
resistance vessels in different parts of the body, as well as energy
required
to
overcome
pulsations
which
persist
even
in
the
microcirculation.
Clinical applications of modern development of dynamics
of
the
vascular
system
have
initiated
both
invasive and noninvasive
technological development and improvement in the accuracy of assessing
