abdullah

1. ARTERIAL PRESSURE
• The mean arterial pressure (MAP) is defined as the
average arterial pressure during a single cardiac cycle .
• As blood is pumped out of left ventricle in to the
arteries pressure is generated . The MAP is determined
by Cardiac Output (CO).Systemic Vesicular Resistance
(SVR) and Central Venous Pressure (CVP).
• MAP= (CO*SVR ) + CVP
• (As CVP is near 0 mm Hg relationship can be simplified
as below)
• MAP = (CO*SVR)

2. • In practise the mean arterial pressure (MAP) is derived
from a patients Systolic Blood Pressure (DBP )
• Normal(MAP)is between 65 mm and 110 mm of Hg
• MAP=DP+1/3 Pulse Pressure ( PP=SP-DP)
CLINICAL SIGNIFICANCE
• MAP is better indicator of tissue perfusion than SBP
• Hence MAP is calculated for the management of
patients with acute conditions when there is a concern
for appropriate organ perfusion.

3.  Pulse wave velocity (PWV) is a measure of arterial stiffness.
 The properties of the arterial wall, thickness and the arterial
lumen diameter are the major factors influencing (PWV).
 Velocity of pulse wave is independent and much higher than
the velocity of blood flow max velocity of blood flow is only 50
cm/s.
 The rate of travel of the pulse wave is about
• 4 meters sec in aorta and its branches.
• 8 meters /sec in the large arteries .
• 16 meters /sec in the small arteries .
 Aortic pulse wave velocity is a measure of aortic stiffness. It is
measured with ultrasound
 Aortic pulse wave velocity is the predictor of cardiovascular
mortality in the hypertensive subjects
Velocity of circulation of pulse waves

4. Cardiac cycle causes flow & pressure waves
 Relationship of pressure to flow is not simple
resistance but mechanical impedance which is time
dependent resistance is time dependent
 Mechanical impedance consists of
• Viscous impedance that opposes flow.
• Compliant impedance that opposes volume.
• Inertial impedance that opposes change of flow.
 Because of these resisive compliant and inertial
properties the pressure and flow waves are different .

5. Cardiac cycle causes flow & pressure waves
With increasing distance from the heart in the
large arteries the pressure curves become
steeper and the peak narrower and an
important secondary pressure oscillation
appears during diastole .
As the pressure wave travels down the large
arteries it gets distorted but not damped .
MAP falls slightly with increasing distance
from the heart.

6. Distortion of pressure waves
The pressure wave in the aorta is more
complex than a simple sine wave.
The complex waveform can be thought of the
algebric sum of many individual sine cosine
waves each with its own amplitude frequency
and phase.
The precise mathematical method by which
complex waveforms are broken down into
simpler components is called Fourier analysis.

7. Cardiac cycle causes flow & pressure waves
In terminal arteries and arterioles damping of
pressure waves predominates over distortion
because
 Increase in number of parallel vessels
increases aggregate compliance damping the
pressure waves.
 Having a small radius increases resistance
In capillaries damping is so severe that pulsations
do not occur and blood flow is continuous

8. Pulse wave harmonics
 One of the most useful tools of arterial dynamics is the
Fourier analysis of the complex pulse waves in to their
simple sinusoidal harmonic components.
 These harmonics are the simple functions described by
relatively simple mathematics so that calculations on
them are feasible .
 Principle of superposition is applied in the arteries .
 Summation of these harmonics leads in to a new
complex waves.
 Digital computer is used to carry out the Fourier
analysis .

9. Evaluation of pulse wave morphology
by Fourier’s harmonic analysis
Evaluation of pulse waves on five segments of
lower limb in a recumbent healthy subject by
means of Fourier's analysis show following
phenomenon
:: constant and marked accentuation of the
amplitude of the second harmonic.
:: distinct diminution of the amplitudes of
further higher harmonics.
:: relative augmentation of amplitude in a distal
direction as a manifestation of mounting
impedance towards periphery.

10. Distortion of pressure waves
• Vessels become more stiffer towards the
periphery increasing wave velocity especially for
higher frequency components.
• Pressure waves bounce off the end of the arterial
tree and reflect back up the vessels.
• When we summate these various effect on the
sine wave and cosine wave components
downstream the reconstructed pressure wave
has a different (distorted) shape than the original
wave.

11. Circulation time
The time required for the blood to flow between two
given points .
It measures the average linear velocity of blood.
The time taken for the blood to pass through a given
circuit of the vascular system, for Ex; the pulmonary or
systemic circulation, from one arm to another, from
one arm to tongue, or from arm to lung; it is measured
by the injection into an arm vein of a substance, such
as sodium dehydrochlorate,ether,fluorescein,
histamine, or a radium salt which can be detected
when it arrives at another point in the vascular system.

12. Factors influencing circulation time
• Increased cardiac output.
• Exercise.
• Excitement.
• Adrenaline.
• Rise of BMR-all these factors increase the velocity
of blood and decrease C.T.
• C.T is important in diagnosis of right and left
sided failure, in differentiating bronchial and
cardiac asthma , myxoedema etc.