Mean arterial pressure

Overview
The mean arterial pressure (MAP) is a term used in medicine to describe a notional average blood pressure in an individual. It is defined as the average arterial pressure during a single cardiac cycle.

Calculation
$$MAP = (CO \times SVR) + CVP$$, where
 * $$CO$$ is cardiac output
 * $$SVR$$ is systemic vascular resistance
 * $$CVP$$ is central venous pressure

$$CVP$$ is usually small enough to be neglected in this formula.

Estimation
At normal resting heart rates $$MAP$$ can be approximated using the more easily measured systolic and diastolic pressures, $$SP$$ and $$DP$$:


 * $$MAP \simeq DP + \frac{1}{3}(SP - DP)$$

or


 * $$MAP \simeq \frac{2}{3}DP + \frac{1}{3}SP$$

MAP = [(2 x diastolic) + systolic] / 3

or equivalently


 * $$MAP \simeq DP + \frac{1}{3}PP$$

where $$PP$$ is the pulse pressure, $$SP-DP$$

At high heart rates $$MAP$$ is more closely approximated by the arithmetic mean of systolic and diastolic pressures because of the change in shape of the arterial pressure pulse.

Clinical significance
$$MAP$$ is considered to be the perfusion pressure seen by organs in the body.

It is believed that a $$MAP$$ of greater than 60 mmHg is enough to sustain the organs of the average person under most conditions.

If the $$MAP$$ falls significantly below this number for an appreciable time, the end organ will not get enough blood flow, and will become ischemic.