Korotkoff sounds

Measuring blood pressure is one of the first practical skills that medical students are taught. Throughout our careers we will do this simple procedure countless times. We know that we listen for noises and these correlate to the systolic and diastolic pressure. But have you ever wondered what causes these sounds? I was taught that the Korotkoff sounds are due to turbulent blood flow. But I was not convinced and decided to look into it further.

In 1905 during a conference at the Imperial Medical Academy in St Petersburg, Dr Nicolai Korotkoff announced a new method to determine blood pressure.1 He placed a stethoscope over the brachial artery and inflated a rubber cuff around the upper arm. Korotkoff found that as the cuff deflated he heard different noises--snapping, murmur-like noises, and muffled tones.2

Since then several different theories for what causes Korotkoff sounds have been suggested: the cavitation theory,3 the arterial wall theory,1 the turbulence theory,4 the transmission of heart sounds theory,5 and the water hammer theory.6