The principle of bloodless blood pressure measurement goes back to the Italian physician Scipione Riva-Rocci (1863-1943), therefore the abbreviation RR according to Riva-Rocci is usual for the blood pressure measured on the arm. The apparatus that Riva-Rocci made consisted of a bicycle tube, which he used as a humeral cuff, a rubber balloon to inflate the cuff, and a mercury barometer to measure the pressure in the artery. Riva-Rocci was able to check the disappearance with increasing (sytolic) pressure by touching the wrist at the wrist. This was a big step forward in blood pressure measurement, because until the 19th century, blood pressure could only be determined by a "bloody" method: measuring probes were inserted into the large arteries of the body.
How is today measured?
Even today, as in the days of Riva-Rocci, an inflated pressure cuff exerts pressure on the upper arm, damaging the arteries and severely limiting local blood flow. By releasing the pressure, the typical "Korotkov noise" can be heard with the stethoscope. These are due to the fact that the blood is swirled, and therefore the movement sounds are audible. After reaching the diastolic value, no pulsating noises are more noticeable. The blood pressure (RR) in the arterial arteries normally reaches a value of 120 mmHg in the systole, in diastole it falls by about a third of the value to an average of 80 mmHg.
Natural blood pressure fluctuations
Blood pressure is by and large a stable business. Short-term and temporary changes can be triggered by physical work, a change in position, pain, psychological effects or stress. Blood pressure is also subject to daily fluctuations: the highest values occur in the morning, late afternoon and early evening. During lunchtime (especially after lunch) blood pressure drops significantly, most during the night.