Hemodynamics
of
Large Arteries
135
resistor which dissipates energy. The electrical analog
of
the windkessel
model
of
the arterial system is shown in Fig. 4.5.4.
Fig.
4.5.5:
An
improved windkessel with three-elements.
Z,,
represents the characteristic
impedance
of
the proximal aorta.
A
modified windkessel model (Fig. 4.5.5) that has three-elements
were later proposed. This lumped model
of
the systemic arterial tree has
been widely used.
It consists, in addition to arterial compliance and
peripheral resistance, a characteristic impedance
of
the proximal aorta.
Z,,
as
it
is
termed will be discussed in greater detail in a later section. Its
hydraulic equivalent is illustrated in Fig. 4.5.6.
aortic
arterial
system
valve
LV
Fig.
4.5.6:
The hydraulic equivalent
of
the three-element windkessel, popularly used to
represent the arterial load to the heart.
A
bottle allowing volume displacement subjecting
to pressure variations represents the arterial compliance. The peripheral resistance is
represented by a needle valve whose partial opening and closing allows resistance to flow
to
be varied.
The finite tube geometry and property represents the characteristic
impedance
of
the aorta.
