Hernodynamics
of
Large
Arteries
139
where At is the sampling interval, taken as 10 msec. The nonlinear
model is then reduced to the following expression:
With the measured aortic flow as the input, a numerical procedure can be
programmed to solve P(ti), C(P) and the aortic pressure
110
1
73
!
I
1
I
I
1
0.0
0.1
0.2
0.3
0.4
0.S
tim
(see)
Fig.
4.5.10:
The
nonlinear and linear model predicted aortic pressure waveforms,
compared
to
the measured aortic pressure. Dotted line: linear windkessel model; dashed
line: nonlinear pressure-dependent compliance model.
This nonlinear model predicted aortic pressure accurately, as shown
in Fig.
4.5.10.
The linear three-element model predicted the measured
aortic pressure with less accuracy, although the
gross
features are
evident.
The model-based arterial compliance plotted as a function of
pressure
for
a complete cardiac cycle with a normal blood pressure level
is shown in Fig.
4.5.11.
It is clear from this figure that compliance is
relatively independent
of
both pressure and flow in the early systole and
maintains a value close to its maximum
This
during this period.
