# Mean arterial pressure

Mean arterial pressure is the average value of blood pressure during one heart cycle.

## Calculation of mean arterial pressure

Comparison of mean pressure (orange) with systolic and diastolic

The mean arterial pressure value cannot be calculated as the arithmetic mean of the systolic and diastolic pressure values. The main reason for the difficulty of such a calculation is the duration of diastole, which is about twice as long as the duration of systole. For this reason, the mean arterial pressure value is closer to the diastolic pressure value.

In physiological blood pressure values (120/80 mmHg) the mean arterial pressure value is 93,3 mmHg.

For an accurate calculation, it would be necessary to know the detailed course of arterial pressure values during the entire cardiac cycle. This condition is partially only met during invasive measurements. For this reason, relations using the fact that SAT depends significantly on the value of systolic and diastolic pressure are used to estimate mean arterial pressure:

The mean arterial pressure (SAT) can be calculated as the sum of one-third of the systolic pressure (ST) and two-thirds of the diastolic pressure (DT).

${\displaystyle SAT={\frac {1}{3}}ST+{\frac {2}{3}}DT}$

Another calculation for mean arterial pressure is the sum of diastolic pressure (DT) and one-third pulse pressure (PT).

${\displaystyle SAT=DT+{\frac {1}{3}}PT}$

The pulse pressure value can be calculated as the difference between systolic and diastolic pressure.

${\displaystyle PT=ST-DT}$

In practice, it should be borne in mind that these calculations are valid in situations where the pressure curve has a physiological course. If blood pressure values are significantly modified by a pathological process (affecting, for example, a vessel wall or blood viscosity), the actual mean arterial pressure value may differ from the value calculated using the above relations.

## References

### Source

• KITTNAR, Otomar, et al. Lékařská fyziologie. 1. edition. Praha : Grada, 2003. 790 pp. ISBN 978-80-247-3068-4.
• TROJAN, Stanislav, et al. Lékařská fyziologie. 4. edition. Praha : Grada, 2003. 771 pp. ISBN 80-247-0512-5.