Basics of a pressure wave

1. Peripheral Arterial Pressure Curves
Dr.Praveen Nagula

2. What are the pressure waves?
Let’s see…

3. Percussion wave and Tidal wave

4. Normal Pressure wave in the
arterial system and its
components

5. What is systole and diastole in the pressure wave

6. The components of systole and diastole in the pressure wave

10. Waveform (a) represents the radial waveform of a 25 year old person, (b) is 47 years old,
and (c) is 80. Now, those pink overlays are purely in the author's imagination (they weren't a
part of the original image from McVeigh et al), but they illustrate the point. Nice compliant
arteries of the youth produce less reservoir pressure because they distend readily in
response to systolic flow. In old age, the reservoir is much less compliant, and the pressure
generated by pumping blood into it will be higher, deforming the shape of the diastolic run-
off.

11. Pathological

16. Back to basics ..

17. How does the pulse wave originate?
The Pulse that is palpated is the pressure wave.
Pressure wave is generated by radial stretch of the ascending aorta brought
about by the left ventricular ejection (directly proportion to the force of left
ventricular ejection).
It is propagated down the aorta and its branches with a finite velocity.
The velocity is faster than the actual forward movement of the blood itself.
The same wave, is the one that perceives in counting the pulse rate by palpating
the radial artery.

18. Velocity of the transmission of the pressure wave varies inversely with the
vascular capacitance.
Accurate measurement of the transmission velocity, valuable information can be
derived concerning the elastic characteristics of the arterial tree.
Transmission velocity increases with age – arteries become less compliant with
advancing age.
Velocity increases progressively as the pulse wave velocity travels from the
ascending aorta towards the periphery.
Vascular capacitance diminishes in the peripheral system – increased velocity.

19. Waveform (a) represents the radial waveform of a 25 year old person, (b) is 47 years old,
and (c) is 80. Now, those pink overlays are purely in the author's imagination (they weren't a
part of the original image from McVeigh et al), but they illustrate the point. Nice compliant
arteries of the youth produce less reservoir pressure because they distend readily in
response to systolic flow. In old age, the reservoir is much less compliant, and the pressure
generated by pumping blood into it will be higher, deforming the shape of the diastolic run-
off.

20. The arterial pressure contour is more distorted as the wave is transmitted down
the arterial system.
Changes in the pressure wave from aorta to periphery
1.delay in the time of onset of initial pressure rise associated with the transmission
delay.
2.the high- frequency components of the pulse, such as the incisura, are
dampened out and soon disappear.
3.the systolic portions of the pressure wave become narrowed and attain greater
peak values.
4.hump become more prominent on the diastolic portion of the pressure wave.

24. The changes in the contour of the pulse wave are pronounced in young
individuals, but the magnitude of the alterations diminishes with age.
In elderly patients with atherosclerosis, the pulse wave may be transmitted virtually
unchanged from the ascending aorta to the periphery.

25. Waveform (a) represents the radial waveform of a 25 year old person, (b) is 47 years old,
and (c) is 80. Now, those pink overlays are purely in the author's imagination (they weren't a
part of the original image from McVeigh et al), but they illustrate the point. Nice compliant
arteries of the youth produce less reservoir pressure because they distend readily in
response to systolic flow. In old age, the reservoir is much less compliant, and the pressure
generated by pumping blood into it will be higher, deforming the shape of the diastolic run-
off.

26. Why there is dampening of the high frequency components ?
Viscoelastic properties of the arterial walls

27. What are the mechanisms for the peaking of the pressure wave ?
1.Reflection
2.Tapering
3.Resonance
4.Changes in transmission velocity with pressure level.

29. REFLECTION
Whenever significant changes in configuration or in dimensions occur ( such as at
points of branching), pressure waves are reflected backward.
Pressure at any point in time and space is determined by the algebraic summation
of an antegrade incident wave and retrograde reflected waves.
80% of the incident wave is reflected back from the peripheral bed at normal levels
of peripheral resistance.
When the bed is dilated, the fraction decreases, whereas vasoconstriction has the
opposite effect.

30. TAPERING
Distally along the aorta or any large artery
The lumen progressively narrows beyond each successive branch.
Pressure wave becomes amplified as it progresses down a tapered tube.

31. RESONANCE
Composed a series of sine waves (Fourier series) consisting of some fundamental
frequency and its harmonics.
Arterial tree resonates at certain of these frequencies, an other frequencies are
effectively dampened.

32. VELOCITY vs PRESSURE
Velocity varies inversely with arterial capacitance.
Capacitance varies inversely with pressure level.
Hence the points on the pressure curve at the higher levels of pressure tend to
travel faster than those at lower pressure levels.
Peak of the arterial pressure curve tends to catch up with the beginning, or foot of
the same curve.
Peaking and narrowing of the curve in more distal vessels such as the femoral
artery.
Reflection and resonance also account for the diastolic humps on these same
peripheral curves.

33. References
https://derangedphysiology.com/main/cicm-
primary-exam/required-
reading/cardiovascular-
system/Chapter%20760/normal-arterial-line-
waveforms
Cardiovascular Physiology, 4th edition
Robert M. Berne, Matthew N.Levy