Mean arterial pressure is the average pressure in the arteries over a full heartbeat, and is what actually determines blood flow to organs — not the systolic number alone.
Normal — adequate organ perfusion.
Borderline low — common resuscitation target is ≥ 65.
Too low to reliably perfuse vital organs.
Elevated.
Given: 120/80 mmHg.
Because diastole lasts longer, the mean sits closer to the diastolic pressure.
The heart spends more of each cardiac cycle in diastole than systole, so the time-averaged pressure sits closer to the diastolic value — hence the one-third/two-thirds weighting.
Roughly 70–100 mmHg. A MAP below about 60–65 mmHg is generally considered too low to reliably perfuse vital organs.
Organ blood flow depends on the average driving pressure across the whole cycle, which is MAP — not the brief systolic peak.
A MAP of at least 65 mmHg is a common resuscitation target, though the ideal value is individualized to the patient and cause.