The term blood pressure refers to the pressure within the arteries as the heart pumps the blood around the body. There are two pressures which are measured, Systolic pressure and Diastolic pressure. Systolic pressure refers to the pressure in the arteries when the heart contracts. Diastolic refers to the pressure in the arteries as the heart relaxes.
By regularly monitoring blood pressure doctors are able to advise patients on avoidance of Hypertension (high blood pressure) and Hypotension (low blood pressure).
In 1730 the first recorded measurement of blood pressure was made by the Reverend Stephen Hales. He inserted a cannula into an artery on the neck of a horse and measured the height of the column of blood in a glass tube. It rose to more than eight foot above the heart level.
It was over a hundred years later in 1896 that Italian physiologist, Scipione Riva-Rocci developed a blood pressure machine which was very similar to modern day machines. Using a Mercury manometer he was able to measure what is now known as Systolic pressure.
It needed further advancement to take a measurement of Diastolic pressure. In 1905 a Russian army surgeon, Nicholai Korotkoff introduced the idea of listening over the brachial artery (in the arm) to detect the turbulence of sounds during the gradual deflation of a cuff. Therefore these sounds are now known as `Korotkoff' sounds.
The Mercury blood pressure machine is still in frequent use these days, but it must be used properly to gain an accurate reading. The cuff is wrapped around the patient's left arm at the same level as the heart and the cuff is inflated until the patient's pulse disappears, then the cuff is gradually deflated.
More accurate electronic blood pressure machines are slowly starting to replace the mercury machines.
