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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


5.8 - Method for the measurement of the blood pressure: listening (microphonic), oscillometric or much more rarely photoplethysmographic.

Once the cuff is inflated, the artery of the arm is compressed and the passage of the blood is stopped. Then, the cuff is gradually deflated, at on average 2 to 3 millimetres of mercury per second.

During this phase, two phenomena occur:

- Auscultatory method


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The noise emitted by the artery changes: when the artery is compressed, the physician listening with his stethoscope or the microphone which «replaces the ears» hears no noise. Then, when the pressure decreases in the cuff, the artery starts to emit a noise: the pressure then measured on the device defines the maximal blood pressure or systolic blood pressure.

Then, the noise continues to be heard during the decrease of the pressure in the cuff, until the noise disappears: the pressure then read on the device defines the minimal blood pressure or diastolic blood pressure.

This method of measurement of the blood pressure is the auscultatory method. It is used by the physician, but also by an automatic measurement of the blood pressure device.


Auscultatory method

- Oscillometric method

The pulsations induced by the artery are different: when the artery is compressed, no pulsation is perceived by the device, then when the pressure decreases in the cuff, the artery starts to emit pulsations: the pressure then measured on the device defines the maximal blood pressure or systolic blood pressure.

During the pressure decrease in the cuff, the oscillations will become increasingly significant, until a maximum amplitude of these oscillations defines the average blood pressure.

Then, the oscillations can still be seen during the decrease of the pressure in the cuff, until they disappear: the pressure then read on the device defines the minimal blood pressure or diastolic blood pressure.

This method of measurement of the blood pressure is the oscillometric method. It is very often used in the automatic device for the measurement of the blood pressure because of its excellent reliability. On the other hand, it is less precise than the microphonic or auscultatory method. Many devices and in particular the automatic devices measuring the blood pressure during 24 hours, use the two measurement techniques.



Oscillometric method

- Photoplethysmographic method

This technique measures the blood pressure at the level of the arteries of the fingers. A small cuff is inflated around the finger, and the pressure is maintained constant in the small cuff. Any variation of pressure on the level of the finger will involve a modification of the pressure in the cuff, which thus translates it into blood pressure.

File last reviewed on : 18 dec 2011
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