Korotkoff sounds

Abstract

In 2005, it will be the 100th anniversary of one of the most far-reaching discoveries in the field of hypertension research: the auscultatory method of blood pressure measurement. Being widely used for a century, the method is named after the Russian physician and scientist, Nokolai Korotkoff (1874–1920) (Fig. 1). Unfortunately, although the method itself, as well as the name of the author, are world-famous, much less is known, even by hypertension experts, about the history of this outstanding discovery and the real role that the author played in the interpretation of the sounds and in the implementation of their use into clinical practice.Fig. 1Nokolai Korotkoff worked in St Petersburg Russian Military Academy. He was a surgeon and his scientific work was in the field of collateral limb blood flow and aneurysms. His major interest was to find signs that could predict whether limb circulation would be viable after ligation of the artery. These investigations were based on the previous works of the famous Russian surgeon N. I. Pirogov, who recommended auscultation of aneurysms in all doubtful cases. Korotkoff started to systematically auscultate the vessels and noticed special sounds, which appeared under the brachial artery when it was compressed by the stethoscope membrane. These sounds were auscultated by other investigators as well, but it was Nokolai Korotkoff who first proposed their use in the measurement of blood pressure. He found that, after compressing an arm with the Riva-Rocci cuff until the distal pulse disappeared, and then gradually decreasing the pressure, a sequence of sounds could be heard under the artery distal to the compression. Korotkoff described the following sequence of sounds: first a sound, then murmurs, loud sounds, decreasing sounds and complete disappearance. These observations are now classified as the five different phases of Korotkoff sounds. The scientist was only 31 years old when he made a short presentation to the Scientific Meeting of the Military Hospital of the Academy on 5 November 1905 concerning an easy non-invasive method of blood pressure measurement, entitled ‘Concerning the probslem of the methods of blood pressure measurement’ [1]. The concept conveyed by the presentation was so innovative and surprising that the audience remained silent for several minutes. Nowadays, we are not surprised to learn that not all members of the Academy Scientific Council approved this discovery with enthusiasm. There are many examples in the history of human knowledge, and in the history of medicine in particular, when revolutionary ideas are met by a rather cool attitude and have a long way to progress before finally becoming accepted. The origin of the sounds became the major object of discussion. Korotkoff believed that an artery cannot produce any sound when it is completely compressed, as well as uncompressed. If the pressure in the cuff is relieved, blood starts coming through the compressed segment during systole, and Korotkoff considered this to be the cause of the first sound and a measurement of systolic blood pressure. When normal blood flow is fully restored, sounds disappear, which in Korotkoff's opinion was a measurement of diastolic blood pressure. However, other scientists thought that the sounds were derived from the heart and could not be used as indicators of blood pressure. Later, Russian scientists and investigators all over the world pursued their investigations towards an understanding of the nature of the auscultatory phenomenon. G. Lang (1908), as well as MacWilliam and Melvin (1914), considered the sounds to be the result of tension in the artery wall. In 1906, a scientist from the same clinic where Korotkoff had been working, M. Krilov, started a series of studies that lasted 30 years and, at the end, in 1935, he came to the conclusion that the origin of the sounds was ‘still a mystery'. Subsequently, many different interpretations have been suggested, and use of either the phase IV or V of Korotkoff sounds was proposed as a measurement of diastolic blood pressure until, finally, phase V was universally accepted, as wisely suggested by Korotkoff. Although our present understanding of the nature of the sounds may have changed, the method remains the standard one for the diagnosis and management of hypertension, and newer devices are still being developed to record Korotkoff sounds. There are few diagnostic methods in medicine that have survived for 100 years, and have not been relegated to historical importance only. St Petersburg, the city where the scientist lived and worked, has decided to organize an International Meeting in 2005 devoted to hypertension investigations from the time of Korotkoff to the present day. It is hoped that this meeting will help the world to know better this outstanding man, and prove to be an important contribution to his memory.