A Horse and a Glass Tube
The first well-known measurement of blood pressure was invasive. In 1733 the English clergyman and scientist Stephen Hales connected a long glass tube to an artery in the leg of a horse and watched the blood rise in the tube. The height of the column told him about the force pushing the blood. The experiment was influential in showing that pressure could be measured, but it required opening a vessel, and it was clearly not suited to a patient in a clinic.
In 1828 the French physician Jean Poiseuille improved the idea by connecting a mercury manometer to an artery, which gave a more compact and practical reading in the laboratory. Mercury columns later became the standard unit: pressure in the clinic is still commonly given in millimeters of mercury, even where no mercury is used.
Measuring Without Cutting
Physicians wanted a way to estimate pressure through the skin. In the mid-nineteenth century the German physiologist Karl Vierordt reasoned that if one pressed on an artery until the pulse beyond it disappeared, the force needed would reflect the pressure inside. His device was awkward and involved weights, but the principle held.
Others refined the approach. Samuel von Basch, a physician in Vienna, introduced a device in the early 1880s, often called the first practical sphygmomanometer, in which a water-filled bulb pressed against the radial artery at the wrist and was connected to a pressure gauge. The word comes from the Greek for pulse. His version gave an estimate of systolic pressure, the highest pressure when the heart contracts, and it began to spread among physicians in Europe. Pierre Potain in France developed a similar instrument using air.
The Cuff Arrives
The decisive change was the cuff. In 1896 Scipione Riva-Rocci, an Italian physician, described a device with an inflatable rubber band wrapped around the upper arm, a rubber bulb for pumping air in, and a mercury column to read the pressure. He would inflate the cuff until the pulse at the wrist vanished, then let air out slowly and note the pressure when it returned. A cuff covered a larger area than a small pad on the wrist and gave steadier, more repeatable results than earlier devices. Later users found that narrower cuffs overestimated pressure, which led to wider bands.
In the United States, the neurosurgeon Harvey Cushing encountered the device in Italy around 1901 and helped introduce it in American hospitals, using it to monitor patients during operations. Cushing is often credited with popularizing it there, though the instrument was becoming known more widely in the same years.
Listening for the Sounds
Riva-Rocci’s method found the systolic pressure only. In 1905 the Russian surgeon Nikolai Korotkov described a way to also estimate the lower, diastolic pressure by listening with a stethoscope over the artery at the elbow while the cuff was slowly deflated. A series of tapping sounds, now called Korotkoff sounds, begins when blood first squeezes through the compressed artery and changes character and then fades as the pressure falls. The numbers at which they start and stop were associated with the systolic and diastolic readings. The surname is spelled Korotkov or Korotkoff depending on the transliteration.
This combination, a cuff, a mercury gauge and a stethoscope, remained the standard clinical method for most of the twentieth century. It also shows how medical tools often depend on each other, since the stethoscope was already well established.
From Curiosity to Routine
For decades after the cuff appeared, many doctors did not routinely take blood pressure. Interest grew in the early twentieth century, helped in part by life insurance companies that noticed a relationship between higher readings and mortality. Over the decades that followed, researchers published population studies linking high blood pressure to heart disease and stroke, and measuring it became a standard part of a physical examination.
Other changes followed:
- The aneroid gauge, a sealed metal capsule with a dial, replaced the mercury column in many settings because it was lighter and more portable, though it needs periodic checking.
- Automatic electronic monitors, using sensors that detect pressure oscillations in the cuff instead of listening for sounds, spread widely from the later twentieth century, including home devices.
- Concerns about mercury as a toxic substance led many hospitals and some countries to phase out mercury devices.
Limits and Cautions
A single reading can vary with posture, stress, cuff size and time of day, and the history of the instrument includes repeated work on improving accuracy and standardizing the method. That is why modern guidance, which this article does not provide, is left to clinicians. The device itself remains conceptually simple: a way to squeeze an artery from the outside and find the pressure at which blood begins to flow.