# Mean arterial pressure

The mean arterial pressure (MAP) is a term used in medicine to describe an average blood pressure in an individual.[1] It is defined as the average arterial pressure during a single cardiac cycle.

## Calculation

Total Peripheral Resistance (TPR) is represented mathematically by the formula:

R = ΔP/QA[2]

R is TPR. ΔP is the change in pressure across the systemic circulation from its beginning to its end. Q is the flow through the vasculature (equal to cardiac output)

In other words:

Total Peripheral Resistance = (Mean Arterial Pressure - Mean Venous Pressure) / Cardiac Output

Therefore, Mean arterial pressure can be determined from:[3]

$MAP = (CO \cdot SVR) + CVP$

where:

## Estimation

At normal resting heart rates $MAP$ can be approximated using the more easily measured systolic and diastolic pressures, $SP$ and $DP$:[4][5][6]

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

or equivalently

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

or equivalently

$MAP \simeq \frac{(2 \times DP) + SP}{3}$

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 $MAP$ that is greater than 60 mmHg is enough to sustain the organs of the average person. $MAP$ is normally between 70 to 110 mmHg[7]

If the $MAP$ falls below this number for an appreciable time, vital organs will not get enough Oxygen perfusion, and will become ischemic.