A normal range for mean arterial blood pressure is 70 to 110, according to GlobalRPh. A minimum of 60 is required to supply enough blood to nourish the coronary arteries, brain and kidneys. If mean arterial pressure falls below 60 for an appreciable length of time, vital organs can be deprived of oxygen. There are various ways of estimating mean arterial pressure, some more accurate than others, according to PhysiologyWeb.
PhysiologyWeb maintains that the best formula for measuring is as follows: mean arterial pressure = diastolic pressure + (1/3) × pulse pressure. Pulse pressure equals systolic minus diastolic pressure. The practice of calculating MAP by averaging diastolic and systolic readings isn't an accurate measure because the ventricles spend only about one-third of the time in systole, which is the working stage of the cycle. Mean arterial pressure is critical because it is a time-weighted average of blood pressure readings in the large arteries during a cardiac cycle. It shows the rate at which the heart pumps blood, the rate of blood flow out of the large arteries and the compliance, or elasticity, of the arterial walls. Together these three factors give a more complete snapshot of cardiac vigor than the popular equation of systolic over diastolic readings.