He Noise of Korotkoff Is the characteristic sound produced on an artery when pressure is reduced below systolic blood pressure, as when 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 Dr. 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 Medical School with the rank of Physician (equivalent to the rank of Doctor of Medicine in the United States).
Korotkoff stayed in Moscow doing his residency in 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 position of assistant at the Military Medical Academy of St. Petersburg.
During the Russo-Japanese war (1904 to 1905), he was sent to Harbin, northeast China, where he worked as a doctor in different hospitals. From 1908 to 1909, he worked in Siberia as a physician in the Vitemsk-Oleklinsk region of Russia.
In 1905, Korotkoff developed a new method for measuring blood pressure . This auscultatory blood pressure measurement method was described in detail for the first time in"Experiments to Determine the Strength 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 S.P. Fedorov and V.A. Oppel and Privat-Docent (equivalent to Associate Professor) N.N. Petrov, unanimously acknowledged that Korotkoff's scientific findings represented an incredibly important discovery, which revolutionized the existing field of heart disease .
During World War I, Korotkoff worked at the military hospital in the city of Tsarskoye-Selo, Russia. After the revolution of 1917 in Russia, he became the senior physician of the Metchnikov Hospital in Petrograd (as it was then called St. Petersburg) and later became a 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 the wounded in the battle led Korotkoff to study the damage to the main 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 for 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 the Ligature of the abdominal aorta The aneurysm in the groin region be performed easily and safely?"
While treating the wounded soldiers they had Aneurysms , Korotkoff set out to find clues that would allow the surgeon to predict the outcome of the ligature of the arteries of traumatized limbs, ie whether the limb would recover or die after surgery.
While attempting to solve this problem, he systematically listened to arteries to estimate the potential strength of arterial collaterals after a major vessel of the injured limb had been ligated.
It 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 of the new method of measuring blood pressure.
In his studies, Korotkoff used the apparatus proposed by Riva-Rocci in Italy in 1896 which contained an elastic inflatable armband around his arm, a rubber bulb to inflate the bracelet, and a mercury sphygmomanometer to measure the pressure of the cuff.
Riva-Rocci measured the systolic pressure by recording the cuff pressure at which the radial pulse was obliterated as determined by palpation. The technique of palpation did not allow the measurement of the diastolic pressure.
Shortly after describing the technique of Riva-Rocci, Hill and Barnard, he reported a device with an inflatable cuff that surrounded the arm and a needle manometer that allowed the diastolic pressure to be measured by the oscillatory method.
This method used the oscillations transmitted to the calibrator when the pulse wave was coming through the compressed artery. When the cuff pressure was slowly reduced from suprasistolic pressure, the onset of definite 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 widespread 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 allowed to investigate the functioning of the cardiovascular system under normal conditions and during different diseases.
Introduced in 1905, Korotkoff's simple and accurate method of measuring blood pressure has been used by doctors, nurses, researchers and paramedics throughout the world throughout the 20th century. The Korotkoff method will certainly continue to be widely used in the 21st century.
Phases of the sounds of Korotkoff
It is believed that Korotkoff sounds 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 intra-arterial pressure typically, produces lower systolic pressures. This is based on a study that found a difference of 25 mmHg between the 2 methods in some individuals.
In addition, there is some disagreement as to whether the Korotkoff IV or V phase correlates more accurately 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 intraarterial pressure measurements and the pressures obtained using the phase.
Phase IV is used alternately to measure diastolic pressure if there is a difference of 10 mmHg or greater between the onset of phase IV and phase V. This may occur in cases of high cardiac output or peripheral vasodilation in children younger than 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.
The sounds of Korotkoff are the sounds that are heard with a stethoscope as the bracelet 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 pulsating sound as the cuff is gradually deflated. The first clear sound of these pulsations is defined as the systolic pressure.
K-2 (Phase 2)
The sounds in K-2 become softer and longer and are characterized by a sharp sound, as the blood flow in the artery increases.
K-3 (Phase 3)
The sounds become clearer and louder than in the K-3 phase, the beep sound is similar to the sounds heard in the K-1 phase.
K-4 (Phase 4)
As the blood flow begins to become less turbulent in the artery, the sounds in K-4 are damped and softer. Some professionals record diastolic during Phase 4 and Phase 5.
K-5 (Phase 5)
In phase K-5, the sounds completely disappear as the 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:
- Detection of hypertension.
- Assess the suitability of a person for a sport or certain occupations.
- Estimation of cardiovascular risk.
- Determination of the risk of various medical procedures.
Auscultatory method of measurement of blood pressure
The auscultatory method (also known as Riva Rocci-Korotkoff or manual method for measuring blood pressure) is the one that hears the sounds of Korotkoff in the brachial artery.
The gold standard for clinical measurement of blood pressure has always been to take a blood pressure using the auscultatory method where a trained health care provider uses a sphygmomanometer and listens to the sounds of Korotkoff with a stethoscope.
However, there are many variables that affect the accuracy of this method. Numerous studies have shown that doctors and health care providers rarely follow established guidelines for taking appropriate manual blood pressure measurements.
Oscillometric method of measuring blood pressure
The oscillometric method is the measurement of pressure variations in the blood pressure cuff caused by the oscillation of blood flow through the brachial artery.
Blood pressure values are then calculated by an algorithm derived empirically. Most automatic blood pressure monitors use the oscillometric method for blood pressure because it is less susceptible to external noise.
Average Blood Pressure
Mean blood pressure is the average blood pressure during a single cardiac cycle (ie, mean arterial pressure in the arteries).
The equation to calculate is PAM = diastolic +1/3 (systolic-diastolic). Average blood 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 an important 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 contributing to the prevalence of hypertension include smoking, stress, drugs, alcohol, nutrition, diabetes, obesity, and limited physical activity.
References
- 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, American Heart Association. Taken from: circ.ahajournals.org.
- Mohan, S. (2010). What are Korotkoff sounds? What are its five phases? 1-2-2017, from Blogger. Taken from: cardiologytips.blogspot.com.
- Maley, C. (2016). Intro to Blood Pressure. 1-2-2017, American Diagnostic Corporation. Taken from: adctoday.com.
- Jahangir, E. (2015). Blood Pressure Assessment. 1-2-2017, from Medscape. Taken from: emedicine.medscape.com.