118
Dynamics
of
the Vascular System
the diastolic pressure wave is abolished during acetylcholine-induced
vasodilation
and
accentuated
during
norepinephrine-induced
vasoconstriction.
Reflection coefficients obtained for the femoral vascular bed are
shown in Fig. 4.4.7. For the control data (circle), the magnitude
of
the
reflection coefficient ranged from 0.42 at
1.6
Hz,
to
0.22
at
9.6Hz.
During vasoconstriction, the reflection coefficient increased to about
0.65
at
1.6
Hz
and 0.32 at
9.6
Hz.
Vasodilation (triangles) decreased the
reflection coefficient to a value less than
0.1
for all frequencies,
essentially abolishing the reflected waves.
I
0
5
I0
FREOUENCY
(HZ)
Fig.
4.4.7:
Reflections arising from the femoral vascular bed during control (circle),
vasoconstriction (square) and vasodilation (triangle). Reflection coefficients were
computed from the three-point method. From Li et al.
(1984).
4.4.3
Augmentation
Index
A simplified index to interpret wave reflection in the aorta, in the time
domain, was introduced by Murgo et al.
(1980).
Ascending aortic
