Diastolic BP is usually determined by the disappearance of sounds, known as phase V. Which phase is commonly used to determine DBP in most adults?

• A. Phase V
• B. Phase I
• C. Phase II
• D. Phase III

Answer: (A)

In auscultatory blood pressure measurement, the diastolic pressure is read at the point where the Korotkoff sounds disappear. This is phase V. As the cuff deflates, sounds appear at phase I (systolic) and continue through phases II–IV, but when the artery stops producing turbulent flow during diastole, the sounds fade away and become inaudible. That last audible sound marks the diastolic pressure for most adults. In some situations, phase IV (muffling) may be used, but phase V is the standard reference for DBP in the majority of adults.