V - How
to measure high blood pressure?
Principles
5.1 - The
most reliable method: to place a probe measuring the pressure directly
in the artery
5.2 - The most
useful method: The measure of the blood pressure using a sphygmomanometer
with a cuff
Measurement
of the blood pressure
5.3 - At rest
at the doctors
5.4 - At rest
at home, using a self-measurement device
5.5 - During
a physical exercise
5.6 - Measurement
by an ambulatory monitoring of the blood pressure during 24 hours
Description of the device
5.7 - The cuff
5.8 - Method
for the measurement of the blood pressure
5.9 - The sphygmomanometer
5.7 -
The cuff
The cuff is a very significant
element in the measurement of the arterial blood pressure. Thus,
this device must be of good quality and adapted to the circumference
of the arm.
For that, there are various
sizes of cuff: a small size for the children, a normal size for the
adults and a large one for the subjects with a large arm.
The cuff contains an inflatable
pocket (the bladder) which, when it is sufficiently inflated, compresses
the artery of the arm (humeral artery).
The width of the bladder must be adapted to the circumference of the arm: classically,
this width must be equal to at least 40% of the circumference of the arm.
Thus, a bladder of 12 centimetres in width must be proposed on a subject
whose arm’s circumference is equal to 30 centimetres.
The widths of the bladder for a child, an adult and an obese
patient are respectively 9, 12 and 15 centimetres. A few manufacturers proposed
mixed cuff, containing a pocket of 9 cm and 12 cm in the same cuff (" Bi-cuff ")
or 12 and 15 cm.
The width of the cuff is
of primary importance in the measurement of the blood pressure because
mistakes can occur if an unsuited cuff is used. Thus, if the blood
pressure is measured with a " normal " cuff (diameter of
the bladder = 12 cm) on a subject with a fat arm, the blood pressure
will be overestimated.
The reverse is also valid
for the children or subjects whose arm is very thin. If the blood
pressure is measured using a " normal " cuff instead of
a smaller cuff (inflatable pocket of 9 cm) the blood pressure is
then underestimated.
This concept is very important
to avoid considering a patient is hypertensive while he is not, just
because a too small cuff has been used.
In order to adapt the cuff
to the arm, the manufacturers propose a marking-system on the bladder:
a dotted line on one extremity of the bladder must be placed during
the rolling up of the cuff around the arm between the two full lines
drawn on the other extremity of the cuff.
Using
these reference marks, the errors are minimized.
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last modified on : 28 sep 2003 |
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