Korotkoff sounds are heard when a blood pressure cuff is applied, allowing healthcare professionals to take a blood pressure reading. The sounds indicate the systolic and diastolic pressure and can be affected by external factors such as noise or movement.
Korotkoff sounds are distinctive sounds that can be heard when a blood pressure cuff is applied and adjusted. They were first described in 1905 by the Russian physician Nikolai Korotkoff. Listening to these sounds with a stethoscope while using a blood pressure cuff allows a healthcare professional to take a blood pressure reading. Many people are familiar with the process of taking blood pressure manually in clinical settings, as blood pressure is a vital sign commonly tested during doctor visits.
Under normal conditions, the movement of blood through the arm artery is not audible. This is because blood flow is not turbulent. In people with arterial disease, sounds may be heard when the flow is stopped. When a blood pressure cuff is applied, it stops blood flow in a stable and predictable manner and can be used to generate information about the patient’s blood pressure.
When a blood pressure cuff is inflated above the systolic blood pressure, no sounds are heard. Blood flow is occluded and therefore does not move through the arm artery at all. As the pressure drops, the first stage of Korotkoff sounds, a loud thump, is heard as blood begins to flow back into the artery. The reading on the cuff at this point equals the systolic blood pressure. As the pressure decreases, the blood moves into the second stage, a hissing sound, followed by the third stage, characterized by a thumping sound as the blood moves through the vessel.
The fourth phase of the Korotkoff sounds is a murmur noise, followed by silence in the fifth phase as the blood pressure equals the diastolic pressure. Blood flow returns to normal with no blood pressure cuff pressure and silence resumes. An experienced practitioner can get an accurate blood pressure reading with one session, while others may require a second reading to confirm. Fully electronic blood pressure reading machines are programmed to listen for Korotkoff’s sounds and take readings as needed.
Things that can interfere with Korotkoff’s sounds can include placing the stethoscope improperly or being in a noisy environment. Patients should also follow healthcare provider directions, including staying still and relaxed to avoid accidentally raising their blood pressure. Talking or moving during the test can interrupt the readings and force the doctor to repeat the test.
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