Hemodynamics
of
Large Arteries
117
Reflection coefficient can also be defined in terms of vascular
impedances.
For a vessel with characteristic
impedance
Z,
and
terminated with vascular load impedance
Z,
the reflection coefficient
r
is given by:
(4.4.1 1)
The reflection coefficient
so
obtained is therefore a complex quantity
with modulus
r
and phase
+r
varying with frequency, as before.
-
0
.5
I
.o
t
(scc)
Fig.
4.4.6:
Pressure waveforms measured in the femoral artery during control
(A),
acetylcholine induced vasodilated
(B),
and norepinephrine induced vasoconstricted
(C)
states. From Li et al.
(1984).
The reflection coefficient can also be defined for a particular vascular
bed.
For
instance, Li et al. (1984) utilized a three-point pressure method
to measure the amount of reflections arising from the femoral arterial bed
during (a) control, (b) acetylcholine-induced vasodilation, and (c)
norepinephrine-induced vasoconstriction states (Fig.
4.4.6).
Notice that
