Korotkoff sounds

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Korotkoff described the sounds made within an artery as the pressure applied around it was reduced from above the occlusive level to ambient. It is used to measure blood pressure.

The first sound is produced by the artery beginning to open with each systole, and is therefore taken as a good indication of the peak pressure in the artery, and thus the systolic pressure.

  • K1 -
  • K2 -
  • K3 -
  • K4 - sounds becomes muffled
  • K5 - fifth phase - is when sounds cease, as the artery is no longer compressed.

In some individuals, the sounds do not completely disappear and so the diastolic value is taken at K4, although K5 is preferred. The WHO recommend the use of phase IV to measure BP in pregnancy, while the US National Heart, Lung and Blood Institute recommends phase V.[1]