sphygmograph

The sphygmograph ( ) was a mechanical device used to measure

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressur ...

in the mid-19th century. It was developed in 1854 by German

physiologist Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

Karl von Vierordt Karl von Vierordt (July 1, 1818 – November 22, 1884) was a German physiologist. Vierordt was born in Lahr, Baden. He studied at the universities of Berlin, Göttingen, Vienna, and Heidelberg, and began a practice in Karlsruhe in 184 ...

(1818–1884). It is considered the first external, non-intrusive device used to estimate blood pressure. The device was a system of levers hooked to a scale-pan in which weights were placed to determine the amount of external pressure needed to stop blood flow in the

radial artery In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm. Structure The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of th ...

. Although the instrument was cumbersome and its measurements imprecise, the basic concept of Vierordt's sphygmograph eventually led to the

blood pressure cuff A sphygmomanometer ( ), a blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury ...

used today. In 1863,

Étienne-Jules Marey Étienne-Jules Marey (; 5 March 1830, Beaune, Côte-d'Or – 15 May 1904, Paris) was a French scientist, physiologist and chronophotographer. His work was significant in the development of cardiology, physical instrumentation, aviation, cine ...

(1830–1904) improved the device by making it portable. Also he included a specialized instrument to be placed above the radial artery that was able to magnify

pulse wave A pulse wave or pulse train is a type of non-sinusoidal waveform that includes square waves (duty cycle of 50%) and similarly periodic but asymmetrical waves (duty cycles other than 50%). It is a