DETERMINATION OF ARTERIAL BLOOD PRESSURE IN MAN
DETERMINATION
OF ARTERIAL BLOOD PRESSURE IN MAN
Aim: To determine the arterial
blood pressure in man by indirect method before and after exerciser.
Principle: It consists of balancing
air pressure against the pressure of blood in the bronchial artery and then
estimating the former by means of a mercury manometer.
Apparatus: Sphygmo manometer and
stethoscope are the instruments which are universally accepted and used to
determine the arterial blood pressure by indirect or clinical method.
Essentially it consists of an inflatable, Cloth -covered flat rubber bag nearly
by wrapping and extension for the cloth covering over the bag and around the
arm like a bandage. It is usually referred to as cuff. On one side the cavity
of the rubber bag is connected to manometer and on the other side it is connected
to a pressure bulb pump by means of rubber tubes.
By
using the pressure bulb, the rubber bag can be inflated to any desired pressure
on the tube leading from the bulb to the bag, there is a needle valve which can
be opened gradually to allow the air to escape, there by reducing the pressure
in the bag as required.
The
manometer consists of a wide glass bulb bottom and a vertical glass tube. The
glass bulb is filled with mercury and is connected with the inflatable cuff.
The column of mercury in the bulb rises or falls in the glass tube depending
upon the inflation or deflation of the cuff. The vertical glass tube on either
side, is celebrated each division indicating 2 mm of. Pressure can be increased
upto 300 mm Hg. from 0 mm Hg.
Position of
the Patient:
Depending upon the condition of the patient, he can be kept in lying position
(supine position on). If he is able to sit, he can sit in ‘a chair what ever
may by the position of the patient, the hand must be kept at the heart level
and the manometer must be kept at the heart level upper arm of the patient must
be bare up to the shoulder.
Procedure: The uninflated cuff is
wrapped around the upper arm neither to tight nor too loosely. The cubital
fosses must be left free the subject is advised, to relax the arm muscles: after
‘setting every thing as said above the determination of Blood pressure is
stated.
Method to
determine blood pressure: There are different methods to determine the blood pressure.
- Palpatory method
- Auscultory method
- Oscillartory method
Among
these, oscillatory method is out of date due to its inaccuracy. Palpators
method is to determine only systolic blood pressure but not the diastolic,
blood pressure. But the auscitatory method is the one by which both can be
determined and also with accuracy.
Palpatory
Method:
With the cuff wrapped around, the upped arm, the pulse is palpated first by
feeling the radial pulse the cuff is inflated to increase the air pressure till
it over comes the blood pressure and obliterates the arterial lumen so that the
pulses no longer felt. The pressure must be raised another 20 mm Hg beyond this
level.
By
means of the valve, the air is allowed to escape very gradually so that the air
pressure falls inside the cuff and the mercury column in the manometer comes
down simultaneously at the same time the pulse also must be examined as the air
pressure falls a point reaches where the pulse appears suddenly, This is the
point where the air pressure and the blood pressure are equal and the pulse
appears. That is known as the systolic pressure, once pulse appears it will
remain as it is. So the diastoic pressure can not be measured by this.
Auscultatory
method:
Here to auscultate the sounds, the stethoscope is used. The branchial artery is
palpated and the place is noted in the cubital fossa to keep the chests piece
of stethoscope.
The
air pressure is raised in the Sphygmomnometer to 20 to 30 mm Hg above the
systolic pressure as determined by palpatory method. Now the air pressure must
be slowly reduced and simultaneously the chest piece of the stethoscope is kept
on the cubital fossa to hear any sounds, it appear.
As
we reduce the compression 3 sounds are heard which finally disappears. Those sounds
appears during determination of blood pressure are known so korot koff sounds.
First
sound- sudden appearance of a clear, tapping sound which corresponds with the systole
of the heart and corresponds with systolic pressure, Second sound with further failing
the air pressure. The sound attains harsh murmurish quality.
Third
sound with still further reduction in the air pressure, the sound become
clearer, louder and gonging type.
Then
finally, with still further reduction in. the air pressure, the sound become
muffled and finally disappears. The appearance of the first sound .is systolic
pressure and the disappearance of the sound is the diastolic pressure.
Normal average
values:
Systolic
B. P. 120. 120+20 nim. Hg
Diastolic
B. P. 75 + 15 mm. Hg.
N.B: The systolic and diastolic pressure are
conventionally written as 120/80 or 130/90 etc.
Precaution: 1) Observe the arterial
pressure only after the subject has been assured and when he is quietly resting
free from excitement and with the arm relaxed. This is relevant, for the
arterial pressure show temporary variations with change of posture after meals,
in excitement etc.
2) Reject the first reading in nervous subject, for
it is often too high. A second reading will more closely represent the true
pressure.
3) When successive estimation to be made the air
pressure in the armlet should be allowed to fall to zero as soon as each reading
has been taken. The work should be quiet and quick.
4) Repeated compression and decompression of the armlet
just before making actual V determination of arterial blood pressure will
remove any spasm of the arterial wall and eliminate the source of in accuracy.
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