
24
K-Sounds: A Primer
Korotkoff sounds, commonly called K-sounds, are the sounds you detect through your
stethoscope when you measure blood pressure with a sphygmomanometer or an aneroid
device. Named for the Russian physician who identified them, there are five phases of K-
sounds, each phase characterized by a distinct volume and quality of sound.
K-sounds are heard through the stethoscope as the blood pressure cuff deflates. The first
sound, K-1, is heard when cuff pressure equals systolic pressure. K-1 is a sharp, tapping sound.
The K-2 phase is characterized by a swishing sound, caused by the swirling currents in the
blood as the flow through the artery increases.
In the K-3 phase, there is a resumption of crisp tapping sounds, similar to those heard during
phase 1.
An abrupt muffling of sound identifies K-4, the fourth phase.
The end or fifth phase is the point at which sounds cease to be heard altogether.
Systolic pressure is registered at K-1 and diastolic at K-5.
K-4 or K-5? There exists some debate about whether K-4 or K-5 should be
recorded as the diastolic BP. In most cases, K-5 is preferred. However, if the
sound persists even after the cuff is completely deflated, it is recommended
that K-4 be recorded as the diastolic blood pressure.
2
You can find more tips like this in the British Hypertension Society‘s
current guidelines for management of hypertension.
2
B Williams, NR Poulter, MJ Brown, M Davis, GT McInnes, JF Potter, PS Sever, S McG Thom, British
Hypertension Society Guidelines, Guidelines for management of hypertension: report of the fourth
working party of the British Hypertension Society 2004 – BHS IV, Journal of Human Hypertension,
2004 18, 139-185.