The first Korotkoff sound represents which blood pressure value?

• A. Systolic blood pressure
• B. Diastolic blood pressure
• C. Mean arterial pressure
• D. Pulse pressure

Answer: (A)

When measuring blood pressure with a cuff, you listen for sounds as the cuff pressure is gradually released. The first audible tapping you hear marks the moment when cuff pressure has fallen to the systolic level, allowing the artery to start opening and blood to flow in a pulsatile, turbulent way. That pressure—the systolic blood pressure—is what the first Korotkoff sound corresponds to. As you continue to deflate, the sounds eventually disappear when the artery stays fully open and the flow becomes smooth, which indicates the diastolic pressure. Mean arterial pressure and pulse pressure are defined or calculated values (mean arterial pressure is generally around diastolic plus about a third of the pulse pressure, and pulse pressure is systolic minus diastolic) and aren’t identified by the first audible sound.