Understanding Blood Pressure Phases: A Comprehensive Guide

In 1905, a Russian surgeon named Nicolai Korotkoff described a new method to determine blood pressure. (See Reference 1.) Korotkoff's method consisted of dividing the process of taking blood pressure into five phases of sound which could be used to determine exactly where a patient's blood flow level was during the process.

Phase One

• During the first phase, the pressure cuff inflates past the systolic pressure and prevents blood from flowing through the artery. The University College London Department of Medical Physics and Bioengineering notes that as a result, "no sounds are heard above the systolic pressure. At the point where cuff pressure equals the systolic pressure, a sharp tapping sound is heard." (See Reference 2.)

Phase Two

• As the blood flow to the brachial artery increases, a swishing or murmur sound is heard. If the cuff is deflated too slowly, an auscultatory gap may occur, which is characterized by a few seconds of silence. This sometimes leads to misreadings in the blood pressure levels.

Phase Three

• Blood flow increases to the artery, and a solid tapping or slapping sound occurs.

Phase Four

• Phase four is characterized by a thumping or blowing noise. The University College London Department of Medical Physics and Bioengineering comments that "some medical practitioners choose to record this point as the diastolic pressure." (See Reference 2.)

Phase Five

• The fifth phase of blood pressure is characterized by silence as the cuff pressure lowers and blood pressure returns to normal.