The principle of blood pressure measurement without blood goes back to the Italian physician Scipione Riva-Rocci (1863-1943), so the abbreviation RR according to Riva-Rocci is commonly used for blood pressure measured on the arm.
The predecessor of
blood pressure monitors of today
The apparatus that Riva-Rocci built consisted of a bicycle inner tube that he used as an upper arm cuff, a rubber balloon to inflate the cuff, and a mercury barometer with which he measured the pressure in the brachial artery.
By palpating the artery at the carpus, Riva-Rocci was able to check for disappearance as the (sytolic) pressure increased. This was a major advance 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 for measurement.
How is it measured today?
Even today, as in Riva-Rocci’s time, pressure is applied to the upper arm by means of an inflated pressure cuff, which congests the arteries and severely restricts local blood flow.
By releasing the pressure, the typical “Korotkow’s noises”, can be heard with the stethoscope. These are caused by the blood being swirled, and therefore the movement sounds are audible. After the diastolic value is reached, pulsating sounds are no longer perceptible.
Blood pressure (RR) in the brachial arteries normally reaches a value of 120 mmHg in systole, and in diastole it drops by about one-third of that value to an average of 80 mmHg.
Natural fluctuations in blood pressure
Blood pressure is, by and large, a stable affair. Short-term and temporary changes can be triggered by physical work, a change in position, pain, psychological influences or stress.
Blood pressure is also subject to diurnal fluctuations: The highest values occur in the morning, late afternoon and early evening. During the midday period (especially after lunch), blood pressure drops significantly, and it drops most sharply during the night.
