178
Dynamics
of
the
Vascular
System
ECG
AoP
LA
small
Vein
7
Velocity
(cm
.see)
0
-
1
sec
Fig.
6.2.2:
Simultaneously recorded electrocardiogram, aortic pressure
(AoP),
left
ventricular pressure (LVP), left atrial
(LA)
small vein velocity and right atrial pressure
(RAP)
in a dog heart. The venous flow velocity was measured
by
a laser Doppler
velocimeter. From Goto et a1
(1988).
6.2.2
Respiration Effects on Venous Pressure and
Flow
Waveforms
Because the major central veins are within the thorax, respiration can
have a profound influence on the central venous pressure and flow
waveforms. In addition, they modify the venous return to the heart.
Moreno
(1978)
provided recordings of venous pressure and flow
waveforms subjecting to such respiratory effects.
Figure
6.2.3
shows
how respiratory pressure changes can modulate the venous pressures
measured in the thoracic and abdominal veins of an anesthetized dog. In
an awake, instrumented dog, the respiratory effect is well illustrated
when simultaneous measurements of pulmonary vein pressure and flow,
vena caval flow, aortic and pulmonary aortic flows are recorded (Morgan
et al.,
1966).
This group of investigators found that vena caval flow
