How is mean arterial pressure approximately calculated in a resting adult?

• A. diastolic pressure + 1/3 pulse pressure
• B. systolic pressure
• C. pulse pressure
• D. diastolic pressure

Answer: (A)

Mean arterial pressure is the average pressure in the arteries over a full heartbeat, and at rest the heart spends more time in diastole than systole, so the value is weighted toward the diastolic pressure. The standard quick estimate adds one third of the pulse pressure (pulse pressure is the difference between systolic and diastolic pressures) to the diastolic pressure. In formula form: MAP ≈ DBP + 1/3(SBP − DBP). For a typical 120/80 reading, the pulse pressure is 40; one third of that is about 13, so MAP ≈ 80 + 13 ≈ 93 mmHg, which matches the usual resting MAP. Using only diastolic would miss the contribution from systole, using only systolic would overstate the average, and using pulse pressure alone ignores the baseline diastolic pressure.