On methods of blood pressure measurement: to 120th anniversary of N.S. Korotkoff’s discovery

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INTRODUCTION

In 2025, we mark the 120^th anniversary the landmark discovery made by Russian physician and surgeon of the Military Medical Academy Nikolai S. Korotkoff, who introduced the auscultatory method for measuring arterial blood pressure in humans.

Owing to its simplicity, accuracy, and accessibility, Korotkoff’s method is used in medical practice worldwide and is recognized as the international reference standard for measuring and assessing arterial blood pressure (BP). Its introduction marked a new era in studying the cardiovascular system’s functional state in both healthy individuals and patients. Firmly established in clinical and research settings, the method laid the foundation for the development of concepts of hypertension and other blood pressure regulation disorders.

ON THE STUDY OF BLOOD PRESSURE: PREREQUISITES FOR A REVOLUTIONARY DISCOVERY

In 1733, the eminent British natural philosopher, inventor, and Anglican clergyman Stephen Hales (1677–1761) published the results of the first acute experiments to measure blood pressure in animals using arterial cannulation, which he had been conducting since 1727. Using these experimental models, Hales described the clinical features of posthemorrhagic shock, accurately estimated cardiac output, and formulated enduring concepts regarding the role of cardiac valves, importance of blood friction within vessels in determining peripheral vascular resistance, and role of arterial elastic recoil in maintaining blood flow during diastole [1, 2]. A few years later, Daniel Bernoulli (1700–1782), a young academician from the St. Petersburg Academy of Sciences and a mathematician, physicist, physician, and professor of physiology at St. Petersburg University, investigated the laws governing blood pressure in his treatise Hydrodynamica, sive de viribus et motibus fluidorum, together with fellow St. Petersburg academician and professor of physiology and mathematician Leonhard Euler (1707–1783). They evaluated the relationship between blood flow velocity and fluid pressure, which was formalized in Bernoulli’s principle: as the velocity of a fluid increases, the pressure exerted by it decreases. Bernoulli inserted a tube into a thinner one of flowing liquid and observed that the height to which the liquid rose in the perforating tube depended on the flow velocity in the main tube [3]. This principle was subsequently used for over a century to measure blood pressure. Then, Jean Léonard Marie Poiseuille (1797–1861) invented the hemodynamometer, which is a U-shaped mercury manometer, and applied it to the acute measurement of blood pressure in animals, leading to the discovery of one of the most fundamental laws of hemodynamics (See Fig. 1). In his doctoral dissertation, Poiseuille measured pulse-induced arterial dilation and investigated capillary blood flow, establishing that the volumetric flow rate of blood through a vessel is proportional to the fourth power of its radius and depends on the pressure gradient between its ends [4]. Poiseuille’s law is crucial not only for physiology but also for hydrodynamics. It states that the flow of a viscous, incompressible fluid through a long, thin cylindrical tube under steady laminar conditions is directly proportional to the fourth power of the tube radius and inversely proportional to the fluid’s viscosity coefficient.

 

Fig. 1. Poiseuille’s manometer (source: Gscheidlen R. Physiologische Methodik: ein Handbuch der Praktischen Physiologie. Braunschweig: Friedrich Vieweg and Son; 1876:622, fig. 455).

 

$Q=\frac{\pi R^4}{8\eta l}\times \Delta P$,

where Q is the volume of fluid passing through a unit length of the tube per unit time; l is the length of the tube; R is the tube radius; η is the viscosity of the fluid; and ΔP is the pressure difference between the ends of the tube. In medicine, this law is used to assess changes in volumetric flow rate resulting from variations in vessel diameter, such as vascular narrowing due to atherosclerotic lesions.

In 1848, German physiologist Carl Ludwig (1816–1895) combined Poiseuille’s mercury hemodynamometer with a clockwork-driven rotating drum wrapped with a paper strip and equipped with a writing stylus. This device was named the kymograph (from the Greek κῦµα, “wave or oscillation,” and γραφή, “writing”); it produced the first graphical recordings of arterial blood pressure over time (See Fig. 2).

 

Fig. 2. Ludwig’s kymograph (source: Ludwig C. Lehrbuch der Physiologie des Menschen. Band 2: Aufbau und Verfall der Säfte und Gewebe. Thierische Wärme. 2 Auflage. Heidelberg: Akademische Verlagsbuch-Handlung C.F. Winter. 1856. S. 122).

 

Using the kymograph, Ludwig identified consistent relationships between animal respiratory processes and blood pressure. In addition, he developed the Ludwig clock to measure blood flow velocity, another key hemodynamic parameter. However, because these measurements were obtained under acute experimental conditions using arterial cannulation, they remained unsuitable for clinical application [5]. For clinical translation, measurement techniques had to be noninvasive. This was addressed by German physiologist Karl Vierordt (1818–1884) in 1854 by refining Ludwig’s approach, proposing an indirect method of blood pressure measurement based on applying mechanical counterpressure to the radial artery. This external pressure equilibrated intravascular pressure until arterial pulsation ceased, allowing for noninvasive assessment. Vierordt named his device the sphygmograph (from the Greek σφυγµός, “pulse,” and γραφή, “writing”).

In medical history, Vierordt’s sphygmograph is regarded as the first device for noninvasive BP measurement. However, the first accurate measurement of blood pressure in a human was performed invasively, 18 years before the future physician Nikolai Sergeyevich Korotkoff (1874–1920) was born into a merchant family in Kursk. This measurement was performed in 1856 by Lyon-based surgeon Jean Faivre (1824–1871). During an amputation, he cannulated the patient’s femoral artery and connected it to Poiseuille’s mercury manometer; he recorded an arterial pressure in the femoral artery of 120 mmHg, which was slightly lower than the brachial artery pressure of 115–120 mmHg [6]. In 1860, French physiologist Étienne Jules Marey (1830–1904) significantly improved Vierordt’s sphygmograph by introducing a portable version, which he presented to the Biological Society of Paris and Emperor Napoleon III (See Fig. 3). The success of this invention was paradoxically facilitated by a tragic circumstance: during a demonstration of the device, Marey detected an arrhythmia in a court volunteer and publicly warned them of its potential danger. A few days later, the individual died of a cardiac event. Public confidence in the usefulness and diagnostic power of the new medical device significantly increased. Subsequently, Marey was awarded a prize by the French Academy of Sciences.

 

Fig. 3. Marey’s sphygmograph [7] (Fig. 7).

 

Marey’s sphygmograph was even later employed in an early lie detector by the renowned criminologist Cesare Lombroso (1835–1909) [7]. In addition to the portable sphygmograph, Marey developed the plethysmograph, the first instrument to measure both systolic and diastolic blood pressure by recording arterial wall relaxation. Marey adopted Vierordt’s concept of counterpressure; however, his apparatus enclosed the subject’s arm in a water-filled glass chamber connected to a sphygmograph and kymograph to record arterial pulsations. However, the apparatus proved too complex and cumbersome for routine clinical practice.

Among the various types of manometers, the sphygmomanometer (Greek σφυγµός, pulse + µανός, loose + µετρέω, to measure) developed in 1881 by Viennese physician and pathologist Karl Samuel Ritter von Basch (1837–1905) gained the widest acceptance. Furthermore, in this case, patronage by royalty played a role; such support was as valuable to physiologists of that era as it was to opera composers. Von Basch was a friend and personal physician of Archduke Ferdinand Maximilian of Austria. His august patient briefly became Emperor of Mexico, and the physician accompanied him there. Maximilian I failed to retain the throne and was executed 3 years later by republican forces during the civil war. Von Basch defended his patron to the end, narrowly escaping death himself; he escorted the body of the deposed emperor back to Austria. Upon his return to Vienna, the deceased’s brother, Emperor Franz Joseph I, granted von Basch a title of nobility and supported his scientific work [8]. Von Basch introduced two important technical innovations into blood pressure measurement: compressing a limb using a rubber bag filled with fluid and coupling this bag to a mercury manometer to register the pressure required to occlude an artery. Unlike Marey’s apparatus, von Basch’s sphygmomanometer lacked cumbersome components; its principal advantage was its simplicity. Von Basch’s device was used in the earliest clinical studies of hemodynamic pathology. These investigations demonstrated that patients with atherosclerosis exhibited increased blood pressure, a finding that correlated with Poiseuille’s physical laws of hemodynamics, while patients with fever showed decreased blood pressure, thereby confirming clinical observations. The device accurately indicated only the systolic component of blood pressure. Nevertheless, despite the gradual and logical evolution of instrumental blood pressure measurement, professional caution has always been inherent to physicians. Practical medicine is relatively conservative, a trait that can be beneficial but may also delay the adoption of innovations. In clinical practice, von Basch’s method did not gain widespread acceptance. Somewhat ironically, the British Medical Journal commented on this innovation as follows: “…by using the sphygmomanometer, we impoverish our senses and dull the sharpness of clinical perception” [9]. In 1889, French cardiologist Pierre Potain replaced the water in von Basch’s compression bag with air. Air compression exerted pressure on the arm to displace the mercury column, allowing for recording of systolic pressure and making the device more suitable for clinical use. Subsequently, Austrian pathophysiologist and physician Gustav Gärtner (1855–1937), another representative of the Viennese school, introduced a hollow rubber cuff for his blood pressure instrument, the tonometer. In this design, the cuff was applied to a finger [10]. Finally, in 1896, Scipione Riva-Rocci (1863–1937), an Italian pathologist and pediatrician from Turin, developed a device consisting of a pneumatic cuff with an inflation bulb coupled with a mercury manometer to compress the brachial artery. Additionally, he introduced into practice the method of circumferential compression and pulse monitoring to determine blood pressure levels [11]. The Riva-Rocci device proved more convenient in use, establishing blood pressure measurement in clinical medicine as a fundamental method for assessing the circulatory system’s functional state (See Fig. 4).

 

Fig. 4. Riva-Rocci’s sphygmomanometer (source: Janeway T. The Clinical Study of Blood Pressure. New York and London: D. Appleton and Company; 1904. 300 p.).

 

From 1893 to 1898, Nikolai S. Korotkoff studied at Imperial Kharkiv University and later at Imperial Moscow University, where he graduated with the distinction of physician with honors and began his career as a district physician. He later specialized in surgery, served in the Russian Army during the Boxer Rebellion in China, and worked as a Red Cross physician; for his outstanding service in the care of sick and wounded soldiers, he was awarded the Order of St. Anna, Third Class. On his return journey, he traveled around Eurasia by steamship. In 1903, at the invitation of Professor Sergey P. Fedorov (1869–1936), Korotkoff joined Fedorov’s clinic at the Imperial Military Medical Academy as an assistant. When Korotkoff was in Harbin, he participated in the Russo–Japanese War as a senior surgeon at a Red Cross hospital, engaged in vascular surgery, and began collecting material for his doctoral dissertation. At that time, the Imperial Military Medical Academy clinic routinely measured brachial artery blood pressure using the Riva-Rocci apparatus. However, monitoring arterial compression by palpation of the pulse to determine blood pressure levels was not an ideal method. Measurements often had to be repeated several times to obtain an average. The narrow cuff of the Riva-Rocci device (5 cm wide) produced inaccurate readings. Although accuracy improved in 1901 when German physician Heinrich von Recklinghausen proposed the 12 cm cuff, the device’s principal limitation remained: compression control based on the pulse did not allow for assessment of diastolic pressure. Nevertheless, this method remained the only practical means available for the routine clinical evaluation of blood pressure (See Fig. 5).

 

Fig. 5. Indirect measurement of arterial blood pressure using a sphygmomanometer (source: Nichols WW, O’Rourke MF. McDonald’s Blood Flow in Arteries. 4th edition. New York: Oxford University Press, Inc. 1998. P. 132.).

 

REVOLUTIONARY DISCOVERY: KOROTKOFF’S METHOD

On November 8, 1905, at a scientific conference for physicians at the Clinical Military Hospital of the Imperial Military Medical Academy, surgeon Nikolai S. Korotkoff delivered a brief report titled, “On Methods of Investigating Blood Pressure” [12]. He observed that when a Riva-Rocci cuff is used on the upper arm and the pressure within it is rapidly increased until the pulse in the radial artery disappears, no sounds can be heard over the brachial artery. However, as the pressure is gradually decreased, short, faint sounds first appear; with further lowering of the mercury level in the manometer, murmurs and louder sounds become audible. Their intensity then gradually decreases until eventually all sounds disappear completely. This regular sequence, first discovered by Korotkoff, formed the basis of the auscultatory method of measuring blood pressure in humans [13]. Experiments conducted in animals yielded positive results. Korotkoff noted that the use of a binaural stethoscope combined with the Gärtner tonometer significantly simplified the procedure; he then proposed his revolutionary method of blood pressure measurement in a single page of just 281 words (See Fig. 6).

 

Fig. 6. Auscultatory measurement of arterial blood pressure [18].

 

Modern proponents of scientometric indicators and science administrators, who often zealously calculate Hirsch indices, sometimes treat such a scientific genre as conference abstracts with disdain, excluding them from consideration and disregarding them when evaluating scientific work outcomes. There are even formal guidelines in which abstracts are a priori regarded as second-rate. For those who hold this view, it is instructive that one of the most frequently cited Russian scientific works worldwide over the past 120 years — a publication that established the global priority of a Russian physician as renowned as Pavlov or Mechnikov—was precisely a set of abstracts from a local scientific and practical conference. The issue lies not in the genre or length of the text, but in its scientific content.

GENERAL PRINCIPLES OF HYDRODYNAMICS AS APPLIED TO BLOOD FLOW IN VESSELS: THE BIOPHYSICAL NATURE OF KOROTKOFF SOUNDS

Fluid flow through vessels may be laminar or turbulent. When fluid layers move parallel to one another without mixing, the flow is considered laminar. When fluid motion is accompanied by mixing of layers due to the formation of vortices, the flow is referred to as turbulent. The transition from one type of flow to the other is determined by the Reynolds number (R_e):

$R_e=\frac{\rho \upsilon d}{\eta }$,

where ρ is the fluid density, υ is the linear velocity of fluid motion, d is the vessel diameter, and η is the fluid viscosity.

For each fluid, a critical Reynolds number (R_ecrit) exists, which serves as a conventional boundary distinguishing the type of flow. At R_e > R_ecrit, the flow is considered turbulent; at R_e < R_ecrit, it is laminar.

Cardiac activity and blood movement through vessels are accompanied by rhythmic changes in arterial vessel volume and blood pressure. It is customary to distinguish three groups of parameters that integrally characterize blood circulation. The first group comprises blood flow velocity; the second, blood pressure; and the third, total peripheral vascular resistance [13, 14]. The method developed by Korotkoff was based on measuring the minimal external pressure required to compress an artery enough to cease blood flow. In his monograph, Savitsky reported that, under certain conditions, the pressure within the cuff is transmitted to the artery located beneath it without significant losses [15]. Yakovlev noted that as compression cuff pressure exceeds systolic levels, limb segment hemodynamics are characterized by collapsed veins and arteries and blood pooled within the capillary bed [12]. These progressive changes in blood flow culminate in the complete closure of the pulsating arteries. This marks the start of blood pressure measurement according to Korotkoff’s method.

When cuff pressure is decreased to the systolic level, the first event is a brief opening of the vessel as the sum of the intrinsic hydrostatic and dynamic pressures of the blood overcomes the external pressure exerted by the cuff. This is accompanied by a short sound or tone. With further decreases in cuff pressure, each subsequent pulse wave leads to an avalanche-like prolongation of the vessel opening period, resulting in increased sound intensity. This continues until the artery is fully opened or until cuff pressure falls to the diastolic level. At this point, normal blood flow is re-established, restoring of a quasi-stationary flow regime. Simultaneously, a rapid discharge of excess blood volume creates local fluid vortices within the vessel lumen, which are transmitted to the vessel wall by vibrations and are auscultated as the second (diastolic) tone.

During the abrupt ejection of blood accompanying the restoration of normal arterial flow, the gradient of linear fluid velocity increases, resulting in the formation of local vortices within the fluid and in a turbulent flow pattern (See Fig. 7) [14, 15].

 

Fig. 7. Transition from laminar to turbulent blood flow in the aortic arch (1, 2) and in the abdominal aorta (3, 4) (adapted from Savitsky IL, 1974) [15] (Fig. 11).

 

A significant limitation of the method remains the inability to monitor blood pressure continuously over prolonged periods. The principal obstacle is venous occlusion developing distal to the cuff during sustained compression [16, 17].

KOROTKOFF METHOD: THE BEGINNING OF A NEW ERA

In 1910, Korotkoff defended his doctoral dissertation at the Imperial Military Medical Academy, 5 years after his discovery of the auscultatory method for blood pressure determination [18]. Notably, when Korotkoff proposed his auscultatory technique in 1905, the initial reaction of the medical community was one of skepticism, distrust, and caution toward such a bold idea. This criticism was not unexpected: physicians trained in the classical traditions of the time, who did not yet understand the nature of the Korotkoff sounds and who placed primary emphasis on direct physical contact with the patient in diagnostic practice, were wary of ideas that were revolutionary for that era. However, this did not prevent the rapid and widespread adoption of the Korotkoff method. A new era in the study of the cardiovascular system’s functional state began, founded on a fundamentally new principle of BP measurement. Korotkoff, the herald of this new era, remained above all practicing physicians. Devoted to his profession and to his patients, he worked as a surgeon in remote and sparsely populated regions of Russia, including the Vitim-Olekma mining district and Lena goldfields. With the outbreak of the First World War, he served as a surgeon at the Charitable Home for Disabled Soldiers in Tsarskoye Selo. Following the opening of the Mechnikov Hospital in Petrograd, he served as its chief physician until his untimely death in 1920 from pulmonary tuberculosis. Korotkoff’s life was short, but his scientific fame is enduring, although fate did not allow him to continue his scientific path after his remarkable discovery.

120 YEARS SINCE THE REVOLUTIONARY DISCOVERY OF KOROTKOFF

Currently, questions remain highly relevant—particularly in light of the approaching milestone of the 120th anniversary of Korotkoff’s discovery of the auscultatory method for measuring blood pressure in humans [16, 19]: Why does the Korotkoff method of blood pressure measurement remain relevant to this day? Can modern science continue the work of this great physician and refine a method that has become a reference standard?

The Korotkoff method allows for the accurate determination of one of the key hemodynamic parameters, that is, BP. The simplicity and accessibility of measuring this vital homeostatic indicator make the Korotkoff method indispensable. The uniformity and invariability of the biophysical processes underlying the formation of Korotkoff sounds ensure high reproducibility and standardization of blood pressure measurements. This enables the auscultatory method to be applied under virtually any conditions and used in routine clinical practice and in various functional studies of the cardiovascular system. There is no longer any debate regarding the origin of Korotkoff sounds, and the method is regarded as the gold standard for the functional assessment of the circulatory system in clinical and research settings worldwide [19].

However, a significant limitation of the method was the inability to monitor blood pressure continuously over prolonged periods. Technological advances in electronics in the early 20th century led to the development of semi-automatic sphygmomanometers, which later became prototypes of ambulatory blood pressure monitoring devices and helped to overcome this limitation. From the 1970s onward, new approaches for measuring blood pressure were introduced, sometimes serving as alternatives to the classical palpatory and the gold-standard auscultatory methods.

In particular, the oscillometric method emerged, based on the registration and analysis of changes in the amplitude of micro-pulsations of air pressure within the cuff. These micro-pulsations represent oscillatory movements of the arterial wall transmitted to the cuff, generated by local vortices and transient turbulent blood flow that occur during decrease of pressure applied to the vascular wall. This method enabled determining blood pressure even in the presence of weak Korotkoff sounds and in cases of a pronounced auscultatory gap (See Fig. 8).

 

Fig. 8. Nikolai S. Korotkoff (1874–1920), Russian physician and surgeon of the Military Medical Academy (collection of the Military Medical Academy).

 

CONCLUSION

Technological progress continues unabated. However, Korotkoff’s landmark discovery became a pivotal starting point, without which modern biomedical science and clinical medicine are now inconceivable.

Review of the history of arterial blood pressure measurement showed that this long and productive journey involved representatives of scientific and medical communities and schools from several countries, each making an invaluable contribution. This history illustrates a profound thought expressed by the physician and writer, a senior contemporary of Korotkoff, Anton P. Chekhov (1860–1904): “There is no such thing as national science, just as there is no national multiplication table. What is national is no longer science.”

ADDITIONAL INFO

Author contributions: A.E. Korovin: conceptualization, data curation, visualization, writing—review & editing; S.V. Mylnikov: conceptualization, visualization, writing—original draft; I.D. Nemeshev: data curation, visualization, writing—original draft; D.V. Ovchinnikov: conceptualization, data curation, visualization, writing—review & editing; M.V. Polyanichko: writing—review & editing; L.P. Churilov: conceptualization, data curation, visualization, writing—review & editing. All authors have approved the publication version and also agreed to be responsible for all aspects of the each part of the work and ensured reliable consideration of the issues related to the accuracy and integrity.

Disclosure of interests: The authors have no relationships, activities, or interests over the past three years related to for-profit or not-for-profit third parties whose interests may be affected by the content of the article.

Funding sources: The study was not supported by any external sources of funding.

Data availability statement: All the data obtained in this study is available in the article.

Generative AI: Generative AI technologies were not used for this article creation.

About the authors

Aleksandr E. Korovin

Saint Petersburg State University; Military Medical Academy

Email: korsyrik@mail.ru
ORCID iD: 0000-0001-5507-6975
SPIN-code: 6157-4453

MD, Dr. Sci. (Medicine), Associate Professor

Russian Federation, Saint Petersburg; Saint Petersburg

Ivan D. Nemeshev

Sechenov University

Email: ivan.nemeshev@mail.ru
ORCID iD: 0000-0003-2655-8857
SPIN-code: 6847-8947

Рostgraduate Student

Russian Federation, Moscow

Dmitriy V. Ovchinnikov

Military Medical Academy

Email: marianiks777@gmail.com
ORCID iD: 0000-0001-8408-5301
SPIN-code: 5437-3457

MD, Cand. Sci. (Medicine), Associate Professor

Russian Federation, Saint Petersburg

Maria V. Polyanichko

Lesgaft National State University of Physical Education, Sport and Health

Author for correspondence.
Email: marianiks777@gmail.com
ORCID iD: 0009-0009-7529-6452
SPIN-code: 3375-5520

Cand. Sci. (Pedagogical), Associate Professor

Russian Federation, Saint Petersburg

Sergey V. Mylnikov

Eco-Vector LLC

Email: s.mylnikoff@eco-vector.com
SPIN-code: 8162-6020
Russian Federation, Saint Petersburg

Leonid P. Churilov

Saint Petersburg State University

Email: l.churilov@spbu.ru
ORCID iD: 0000-0001-6359-0026
SPIN-code: 8879-0875

MD, Cand. Sci. (Medicine), Associate Professor

Russian Federation, Saint Petersburg

References

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