Which Korotkoff phase corresponds to systolic BP?

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

Answer: (D)

Main concept: systolic blood pressure is determined by the first Korotkoff sound heard as the cuff deflates. When the cuff pressure drops to the level just above the systolic pressure, blood begins to spurt through the artery during each heartbeat, producing a tapping sound. That first audible tapping marks Korotkoff Phase I and is taken as the systolic BP. As deflation continues, sounds change through the later phases (a softer murmur in Phase II, a crisper tapping in Phase III, muffling in Phase IV, and eventual disappearance in Phase V). Diastolic BP is typically the pressure at which sounds disappear, not the first sound.