The Korotkoff sounds n ways to measure BP

Korotkoff sounds - There are five sounds which are heard as the blood pressure in the sphygmomanometer cuff is released during the measurement of arterial pressure; these are described as:

• Korotkoff I is a sharp thud
• Korotkoff II is a loud blowing sound
• Korotkoff III is a soft thud
• Korotkoff IV is a soft blowing sound
• Korotkoff V is silence

The sounds heard over an artery when blood pressure is determined by the auscultatory method.


Korotkoff are the sounds that medical personnel listen for when they are taking blood pressure using a non-invasive procedure. They are named after Dr. Nikolai Korotkoff, a Russian physician who described them in 1905, when he was working at the Imperial Medical Academy in St. Petersburg.

Description
The sounds heard during measurement of blood pressure are not the same as the heart sounds 'lub' and 'dub' which are due to the closing of the hearts valves. If a stethoscope is placed over the brachial artery in the cubital fossa in a normal person (without arterial disease), no sound should be audible. As the heart beats, these pulses are transmitted smoothly throughout the arteries and no sound is produced.

If the cuff of a sphygmomanometer is placed around a patient's upper arm and inflated to a pressure above the patient's systolic blood pressure, there will similarly be no sound audible. This is because the pressure in the cuff is high enough such that it completely occludes the blood flow. It is similar to a flexible tube or pipe with fluid in it that is being pinched shut.

If the pressure is dropped even with the patient's systolic blood pressure, the first Korotkoff sound will be heard. As the pressure in the cuff is the same as the pressure produced by the heart, some blood will be able to pass through the upper arm when the pressure in the artery rises during systole. This blood flows in spurts as the pressure in the artery rises above the pressure in the cuff and then drops back down, resulting in turbulence that results in audible sound.

As the pressure in the cuff is allowed to fall further, thumping sounds continue to be heard as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and dropping back below the pressure in the cuff.

Eventually, as the pressure in the cuff drops further, the sounds change in quality, then become muted, then disappear altogether. As the pressure in the cuff drops below the diastolic blood pressure, the cuff no longer provides any restriction to blood flow allowing the blood flow to become smooth again with no turbulence and thus produce no further audible sound.

Korotkoff actually described 5 types of Korotkoff sounds:

1.The first Korotkoff sound is the snapping sound first heard at the systolic pressure.
2.The second sounds are the murmurs heard for most of the area between the systolic and diastolic pressures.
3.The third and-
4.the fourth sound, at pressures within 10 mmHg above the diastolic blood pressure were described as "thumping" and "muting".
5.The fifth Korotkoff sound is silence as the cuff pressure drops below the diastolic blood pressure.

Traditionally, the systolic blood pressure is taken to be the pressure at which the first Korotkoff sound is first heard and the diastolic blood pressure is the pressure at which the fourth Korotkoff sound is just barely audible. However, there has recently (2000 onwards) been a move towards the use of the 5th Korotkoff sound (i.e. silence) as the diastolic blood pressure, as this has been felt to be more reproducible.

An auscultatory gap is the interval of pressure where Korotkoff sounds indicating true systolic pressure fade away and reappear at a lower pressure point during the manual measurement of blood pressure. The improper interpretation of this gap may lead to blood pressure monitoring errors: namely, the falsely low recording of systolic blood pressure.

The auscultatory gap can be mistaken for the silence that occurs when the cuff pressure exceeds the systolic pressure. In this setting, the true systolic pressure can be elucidated by palpating the radial artery pulse. It is therefore recommended to palpate and auscultate when manually recording a patient's blood pressure.

There is evidence that auscultatory gaps are related to carotid atherosclerosis and to increased arterial stiffness in hypertensive patients, independent of age.

Although these observations need to be confirmed prospectively, they suggest that auscultatory gaps may have prognostic relevance.