Korotkoff

Korotkoff refers to a set of sounds heard through a stethoscope during the auscultatory method of measuring blood pressure with a cuff. The sounds were described by Russian physician Nikolai Korotkoff in 1905, and the phenomenon that bears his name is used to determine systolic and diastolic pressures without invasive procedures.

In practice, the cuff is inflated above the expected systolic pressure and then gradually deflated while the clinician listens over a peripheral artery, usually the brachial artery. As the cuff pressure falls, a sequence of five phases of sound is observed:

Phase I: the first appearance of a clear tapping sound, corresponding to the systolic blood pressure.

Phase II: a softer, longer murmur following Phase I.

Phase III: a crisper, louder tapping sound.

Phase IV: the sound becomes muffled and fades.

Phase V: the sounds disappear completely; in most guidelines, diastolic pressure is read at the point of disappearance (though some guidelines use Phase IV for diastolic in certain populations).

These sounds underpin the conventional auscultatory method for indirect blood pressure measurement and remain a standard reference in clinical practice, though automated oscillometric devices are also widely used. The concept is foundational to noninvasive cardiovascular assessment, and the term “Korotkoff sounds” is widely employed in medical literature and instruction.