A patient has an arterial blood pressure of 120/80 mmHg and a regular heart rate. His calculated mean arterial pressure is closest to:

• A 100 mmHg
• B 87 mmHg
• C 93 mmHg ✓
• D 107 mmHg

Explanation

Mean arterial pressure equals diastolic pressure plus one third of the pulse pressure: 80 plus 40 divided by 3, giving approximately 93 mmHg. The one third weighting exists because at rest, diastole occupies about two thirds of the cardiac cycle while systole occupies one third, so time-weighted average pressure lies closer to diastolic than to systolic values. Taking the arithmetic midpoint of 100 mmHg ignores this asymmetry. At higher heart rates, systole lengthens relatively and the weighting shifts toward one half.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.