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Definition of high blood pressure
What to do in case of hypertension?
For a better understanding of blood pressure The follow-up of a high blood pressure
High blood pressure damage High blood pressure and special cases
Why does high blood pressure exist? The self-measurement of blood pressure
How to measure high blood pressure? About Us
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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.


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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).

- 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.

- 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.

- 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 reviewed on : 18 dec 2011
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