It is not impossible that in a few years time, following the prohibition of the mercury, this method will be replaced by another automatic one.

10.2.1 – The self-measurement device using a stethoscope (microphonic method)

After the inflation of the cuff, the artery of the arm is compressed and the blood is blocked. Then, the cuff is gradually deflated, at on average 2 to 3 millimetres of mercury per second. During this phase, the noise emitted by the artery changes: when the artery is compressed, no noise is audible to the practitioner or the patient who listens with his stethoscope or the microphone which " replaces the ears ".

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 corresponds to the auscultatory method. It is used of course by the practitioner, but also by the automatic device of the measurement of the blood pressure. The cuff of the practitioner is connected with a mercury sphygmomanometer, but mercury is now forbidden for the public’s use.

Thus, cuffs including a membrane able to measure the blood pressure have been created. These cuffs are called aneroid and classically require the use of a stethoscope to hear the noises of the artery.

Sometimes, a microphone has been integrated into the cuff to obtain an automatic device.

nfortunately, this device is not always highly reliable because of the dexterity needed in their handling and the reduction in the precision of the cuff with time.

Nevertheless, this device has not currently been abandoned.

10.2.2 – The oscillometric method

During the progressive deflating of the cuff, 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 the systolic blood pressure.

Progressively as the pressure decreases in the cuff, the oscillations will become increasingly significant, until the maximal amplitude of these oscillations defining the mean blood pressure.

Then, the oscillations continue to be audible during the pressure decrease in the cuff, until the time when they disappear: the pressure then read on the device corresponds to the minimal blood pressure or the diastolic blood pressure.

This method of measurement of the blood pressure is the oscillometric method. It is a simple technique, effective and validated by many medical societies. This technique can be easily automated, and can be used as a self-measurement device by a great number of patients with high blood pressure.

Currently, the majority of the self-measurement devices for blood pressure use this technique and the devices are generally reliable.

10.2.3 – The Photoplethysmographic method

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