KOROTKOFF NOISES: PHASES, INDICATIONS AND METHODS - MEDICINE - 2025

The Korotkoff sound is the sound characteristic that occurs on an artery when the pressure is reduced below the systolic blood pressure, as when the blood pressure is determined by the auscultatory method.

The sound represents the arterial oscillation, resulting from the distension of the arterial wall with each cardiac impulse due to partial occlusion of the artery during compression of the cuff.

Measurement of blood pressure

History of Doctor Nikolai Korotkoff

Korotkoff was born in 1874 into a merchant family; he received his high school diploma in 1893 from the Kursk Gymnasium, and in 1898 he graduated cum laude from the Moscow University School of Medicine with the degree of Physician (equivalent to the degree of Doctor of Medicine in the United States).

Korotkoff stayed in Moscow doing his residency at the Department of Surgery. During the Boxer Rebellion in China in 1900, he was sent by the University to China as a Red Cross doctor. In 1902, he completed his residency and began working in the assistant position at the Saint Petersburg Military Medical Academy.

During the Russo-Japanese War (1904 to 1905), he was directed to Harbin, northeast China, where he worked as a doctor in different hospitals. From 1908 to 1909, he worked in Siberia as a doctor in the Vitemsk-Oleklinsk region of Russia.

In 1905, Korotkoff developed a new method for measuring blood pressure. This auscultatory method of blood pressure measurement was later described in detail for the first time in "Experiments to Determine the Force of Arterial Collaterals," his dissertation for the advanced scientific degree of Doctor of Medical Sciences. The dissertation was presented in 1910 to the Scientific Council of the Imperial Military Medical Academy.

Its reviewers, Professors SP Fedorov and VA Oppel and Privat-Docent (Associate Professor equivalent) NN Petrov, unanimously recognized that Korotkoff's scientific results represented an incredibly important discovery, revolutionizing the existing field of heart disease diagnosis.

During World War I, Korotkoff worked in the military hospital in the city of Tsarskoye-Selo, Russia. After the 1917 revolution in Russia, he became the senior physician at the Metchnikov Hospital in Petrograd (as St. Petersburg was then called) and later became the senior physician at the Petrograd Hospital on Zagorodny Avenue. Korotkoff died in 1920; the cause of his death is unknown.

His education and experience in treating those wounded in battle led Korotkoff to study damage to the major arteries. These studies resulted in his discovery of the new method of measuring blood pressure. It is worth noting that the idea for the new method of measuring blood pressure was born during the Russo-Japanese war.

Korotkoff was working to solve the problem that was first formulated as early as 1832 by one of the most respected Russian physicians, Nicolai I. Pirogov, in his dissertation for the degree of Doctor of Medical Sciences, 'Can ligation of the abdominal aorta during the aneurysm in the groin region be performed easily and safely? "

While treating wounded soldiers with aneurysms, Korotkoff set out to find clues that would allow the surgeon to predict the outcome of the ligation of the arteries of the traumatized limbs, that is, whether the limb would recover or die after surgery.

While trying to solve this problem, he systematically listened to the arteries to estimate the potential force of the arterial collaterals after a main vessel in the injured limb had been ligated.

He established that certain specific sounds could be heard during the decompression of the arteries. This specific phenomenon, known in the world literature as "Korotkoff sounds", became the basis for the new method of blood pressure measurement.

In his studies, Korotkoff used the apparatus proposed by Riva-Rocci in Italy in 1896 that contained an inflatable elastic cuff that encircled the arm, a rubber bulb to inflate the cuff, and a mercury sphygmomanometer to measure the cuff pressure.

Riva-Rocci measured systolic pressure by recording the cuff pressure at which the radial pulse was obliterated as determined by palpation. The palpation technique did not allow the measurement of diastolic pressure.

Shortly after describing the technique by Riva-Rocci, Hill, and Barnard, he reported an apparatus with an inflatable cuff that encircled the arm and a needle manometer that allowed diastolic pressure to be measured by the oscillatory method.

This method used the oscillations transmitted to the caliper when the pulse wave came through the compressed artery. When the cuff pressure was slowly reduced from suprasystolic pressure, the occurrence of definitive oscillations denoted systolic pressure, while the change from maximum to minimum oscillations indicated diastolic pressure.

The method of measuring blood pressure, invented by Korotkoff, quickly received wide recognition and became a standard medical procedure.

This method played an important role in the study of various forms of vascular tone alteration and influenced our understanding of the etiology, pathogenesis, and treatment of hypertension. This method also made it possible to investigate the functioning of the cardiovascular system under normal conditions and during various diseases.

Introduced in 1905, the simple and accurate Korotkoff method of measuring blood pressure has been used by physicians, nurses, researchers, and paramedics around the world throughout the 20th century. Korotkoff's method will undoubtedly continue to be widely used in the 21st century.

Phases of the Korotkoff sounds

Korotkoff sounds are believed to originate from a combination of turbulent blood flow and oscillations of the arterial wall. It is noteworthy that some believe that the use of Korotkoff sounds, rather than direct intraarterial pressure typically, produces lower systolic pressures. This is based on a study that has found a 25 mmHg difference between the 2 methods in some individuals.

Furthermore, there is some disagreement as to whether Korotkoff phase IV or V more accurately correlates with diastolic blood pressure. Typically, phase V is accepted as diastolic pressure due to both the ease of identifying phase V and the smaller discrepancy between intra-arterial pressure measurements and pressures obtained using phase.

Phase IV is used alternatively to measure diastolic pressure if there is a difference of 10 mmHg or greater between the onset of phase IV and phase V. This can occur in cases of high cardiac output or peripheral vasodilation, in children under 13 years or pregnant women. Regardless of whether a manual or automated method is used, blood pressure measurement is a key part of clinical medicine.

Korotkoff sounds are the sounds that are heard with a stethoscope as the cuff gradually deflates. Traditionally, these sounds have been classified into five different phases (K-1, K-2, K-3, K-4, K-5).

K-1 (Phase 1)

The clear appearance of the pulsation sound when the cuff gradually deflates. The first clear sound of these pulsations is defined as the systolic pressure.

K-2 (Phase 2)

Sounds in K-2 become softer and longer and are characterized by a high-pitched sound, as blood flow in the artery increases.

K-3 (Phase 3)

The sounds become clearer and louder than in the K-3 phase, the sound of the beats is similar to the sounds heard in the K-1 phase.

K-4 (Phase 4)

As blood flow begins to become less turbulent in the artery, sounds in K-4 are muffled and softer. Some professionals record diastolic during Phase 4 and Phase 5.

K-5 (Phase 5)

In the K-5 phase, the sounds disappear completely as blood flow through the artery has returned to normal. The last audible sound is defined as the diastolic pressure.

Indications

Indications for blood pressure measurement include:

• Hypertension detection.
• Assessing a person's suitability for a sport or certain occupations.
• Estimation of cardiovascular risk.
• Determination of the risk of various medical procedures.

Auscultatory method of blood pressure measurement

The auscultatory method (also known as Riva Rocci-Korotkoff or manual method to measure blood pressure) is the one that listens to the Korotkoff sounds in the brachial artery.

The gold standard for clinical blood pressure measurement has always been to take a blood pressure using the auscultatory method where a trained healthcare provider uses a sphygmomanometer and listens to the Korotkoff sounds with a stethoscope.

However, there are many variables that affect the accuracy of this method. Numerous studies have shown that doctors and healthcare providers rarely follow established guidelines for taking appropriate manual blood pressure measurements.

Oscilometric method of blood pressure measurement

The oscillometric method is the measurement of pressure variations in the blood pressure cuff caused by oscillation of blood flow through the brachial artery.

The blood pressure values ​​are then calculated using an empirically derived algorithm. Most automatic blood pressure monitors use the oscillometric method for blood pressure, as it is less susceptible to external noise.

Mean arterial pressure

Mean arterial pressure is the average blood pressure during a single cardiac cycle (that is, the mean arterial pressure in the arteries).

The equation to calculate is MAP = diastolic +1/3 (systolic-diastolic). Mean arterial pressure is a useful measure since it indicates both general health and the risk of developing various cardiovascular diseases.

Hypertension

Hypertension or high blood pressure is classified as a blood pressure measurement of 140/90 mmHg or higher. According to the American Heart Association, hypertension affects one in three Americans.

Hypertension is a major risk factor associated with many cardiovascular diseases and plays an important role in the progression of congestive heart failure, stroke, heart attacks, kidney failure, and premature death.

Factors that contribute to the prevalence of hypertension are smoking, stress, drugs, alcohol, nutrition, diabetes, obesity, and limited physical activity.

References

1. Shevchenko, Y and Tsitlik, J. (1996). 90th Anniversary of the Development by Nikolai S. Korotkoff of the Auscultatory Method of Measuring Blood Pressure. 1-2-2017, from the American Heart Association. Taken from: circ.ahajournals.org.
2. Mohan, S. (2010). What are Korotkoff sounds? What are its five phases ?. 1-2-2017, from Blogger. Taken from: cardiologytips.blogspot.com.
3. Maley, C. (2016). Intro to Blood Pressure. 1-2-2017, from American Diagnostic Corporatio. Taken from: adctoday.com.
4. Jahangir, E. (2015). Blood Pressure Assessment. 1-2-2017, from Medscape. Taken from: emedicine.medscape.com.