188
Dynamics
of
the
Vascular
System
Cross-sectional area in relation to transmural pressure in collapsible
vessels has also been studied by several investigators.
Kresch and
Noordergrraaf (1 972) computed the shapes of the tube cross-sectional
areas for different
eccentricity for negative transmural
pressures,
beginning with an ellipse cross-section when the transmural pressure
is
zero. The resulting shapes are shown in Fig
6.3.4.
Moreno et al.'s (1970)
experimental findings seem to confirm these theoretically computed
shapes.
I
I
+.oo
b"
p=o.oo
p=1.00
I
I
~
ik=;
p=-1
.oo
p=-2.00
Fig
6.3.4:
Computed cross-sectional area shapes for a collapsible vessel with varying
transmural pressure (p). Zero transmural pressure (p=O)
is
assumed to be
an
ellipse with
eccentricity
k=2.0.
From Noordergraaf
(1978).
6.3.3
Pulse Wave Transmission Characteristics in Veins
The
low
pulse pressure and collapsible nature of veins make pulse
transmission measurements difficult. There are thus few studies. Anliker
et al. (1969) utilized a method that ensure system linearity and avoid
wave reflection effects. This latter is because wave reflection effects
