The History of Sphygmomanometers

The sphygmomanometer is a device for recording blood pressure. Not until the 1700s was a method devised for recording blood pressure; this method was inconvenient and intrusive. A century later, a doctor came up with the basic design for the sphygmomanometer, which permitted accurate blood pressure readings in a clinical setting. The ability to measure blood pressure allowed researchers to discover average blood pressure, the consequences of relatively low or high blood pressure and the effects of factors like diet on blood pressure.

First Methods of Reading Blood Pressure

• The first blood pressure reading was taken in 1773 by a physiologist interested in blood circulation. Stephen Hales inserted a hollow pipe connected to a 12-foot glass tube into an artery in the neck of a horse; the blood rose 9 feet into the glass tube, indicating the blood pressure. His device was known as a manometer. Although improvements were made to its design, methods of measuring blood pressure remained invasive until 1881. They required the insertion of a pipe into an artery.

The Invention of the Sphygmomanometer

• In 1881, Samuel Ritter von Basch--a doctor in Vienna--came up with the basic design for a sphygmomanometer by following up on the research of Karl von Vierordt, who suggested in the 1850s that a non-invasive blood pressure reading could only be taken if the pulse was stopped. Von Basch used a rubber bulb filled with water to apply pressure to the artery until the pulse disappeared. The rubber bulb was attached to a mercury manometer, which measures the pressure of a fluid; the amount of pressure required to obviate the pulse was the blood pressure reading.

Significance of Von Basch's Design

• Von Basch's device was the first non-invasive and portable method for measuring blood pressure. However, it only measured the systolic pressure, which is the pressure as the heart contracts (the first number of a blood pressure reading). Later improvements made to Von Basch's design rectified this.

Improvements Made to the Sphygmomanometer

• In 1896, Scipione Riva-Rocci and Leonard Hill published separate articles in which they introduced a cuff to be placed around the arm; it was inflated by a pump in order to obviate the pulse. This allowed for uniform pressure to be placed on the artery. N.S. Korotkoff, a Russian doctor, used a stethoscope to listen to the sounds from the artery as pressure from the cuff was released. He reported that the pressure reading when the sounds drop off is the diastolic pressure, or the pressure when the heart relaxes. Since Korotkoff's discovery, blood pressure has been measured diastolically and systolically.

The Sphygmomanometer Today

• There are three main types of sphygmomanometers today, including mercury, aneroid (using air pressure) and digital. Mercury is still considered to be the most accurate. No matter the type, a blood pressure measurement is always given in millimeters of mercury (mmHG).