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
5.2 -
The most useful method: The measure of the blood pressure using
a sphygmomanometer with a cuff
- Principle of measurement
The principle of measurement
consists in recording not the blood pressure directly in the artery
but the arterial counter pressure by squeezing the artery on which
the pressure is measured.
Indeed, the doctor uses a cuff (or an arm-band), which will be gradually filled
with air to press the artery below. The doctor listens to, using his stethoscope,
to the noise emitted by blood at the time of its passage in the artery.
When the band is sufficiently
inflated to compress the artery that is below, blood cannot pass
any more and the doctor thus does not perceive any noise. Then, the
cuff is gradually deflated and the noise now perceived defines the
maximal blood pressure (systolic blood pressure). As the band carries
on its deflation, the noise of the artery disappears again and the
physician measures the pressure corresponding now to the minimal
(diastolic blood pressure).
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- 1 -
The device of
measurement includes an inflatable cuff, a dial of measurement
and a stethoscope.
The bladder is
inflated until the cuff compresses the artery of the arm,
the blood does not pass anymore: the stethoscope perceives
no noise. |
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- 2 -
Then the cuff
is deflated slowly, the blood goes through the artery again:
the stethoscope perceives a noise and the value of the
blood pressure is read at the same time on the dial.
The blood pressure
measured at this moment is the maximal blood pressure,
the systolic blood pressure. |
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- 3 -
The cuff continues
to deflate slowly. The blood passes again and the stethoscope
perceives a noise. |
 |
- 4 -
The more the cuff
deflates and the less audible the noise will be by the
stethoscope, until it disappears completely: the blood
pressure is read on the dial and defines the minimal, i.e.
the diastolic blood pressure. |
- Precision
of measurements: comparison of the values of the blood pressure
between a pressure probe introduced in the artery and the arm-band
measurement.
The studies have shown
that the arm-band device (those which are generally used) underestimate
the maximal blood pressure by 10 millimetres of mercury and over-estimate
by 10 millimetres of mercury the minimal blood pressure.
For example, a person who
has a blood pressure of 140/90 millimetres of mercury (14/9) has
in fact a pressure of 150/80 millimetres of mercury if a probe in
the artery measures the pressure.
| File
last modified on : 28 sep 2003 |
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