134
Dynamics
of
the
Vascular System
This last equation is seen to be equivalent to
or that the diastolic aortic pressure decay (Fig. 4.5.3) from end-systolic
pressure (PeS,)
to end-diastolic pressure (Pd) follows a mono-exponential
manner with a time constant of
z.
The time constant of pressure decay
z,
is determined by the product of resistance and compliance, viz:
z
=
RsC
(4.5.60)
or in terms
of
measured aortic pressure,
and
td
C=
4,
R,
ln-
'd
(4.5.61)
(4.5.62)
Fig.
4.5.4:
The two-element resistance-capacitance electrical analog model
of
the
windkessel. Compliance
is
represented
by
a capacitor and the peripheral resistance
by
a
resistor.
Analysis utilizing simple electric analog, has given the windkessel a
two-element representation.
Arterial compliance is represented by a
capacitor which has storage properties, in this case, electric charge.
Peripheral resistance, with its viscous properties, is represented by a
