# Mean arterial pressure

The mean arterial pressure , abbreviated MAD or MAP (from english mean arterial pressure ), describes in medicine the average of the blood pressure curve over time and is regarded as zuverlässigster parameters for organ perfusion. Normal values ​​are in the range from 70 to 105  mmHg .

Pressure curve in the aorta
Pressure curve in peripheral arteries

## physiology

Mean arterial pressure is the sum of hydrodynamic pressure, which is calculated as the product of cardiac output (CO) and total peripheral resistance (TPR) , and central venous pressure (CVP) , with the latter contributing only a small part and often neglected:

${\ displaystyle {\ text {MAD}} = {\ text {TPR}} \ cdot {\ text {HZV}} + {\ text {ZVD}}}$

The mean arterial pressure is between the systolic and diastolic arterial pressure . Only in arterial vessels very close to the heart does it come close to the arithmetic mean. In peripheral vessels, the blood pressure curve has a narrow maximum and a broad base, so that the mean arterial pressure is closer to the diastolic than to the systolic pressure. A rule of thumb for estimating from the peripherally measured systolic and diastolic pressure is:

${\ displaystyle {\ text {MAD}} = {\ frac {2} {3}} \ cdot {\ text {BD}} _ {\ text {diast}} + {\ frac {1} {3}} \ cdot {\ text {BD}} _ {\ text {syst}} = {\ text {BD}} _ {\ text {diast}} + {\ frac {{\ text {BD}} _ {\ text {syst }} - {\ text {BD}} _ {\ text {diast}}} {3}} = {\ frac {2 \ cdot {\ text {BD}} _ {\ text {diast}} + {\ text {BD}} _ {\ text {syst}}} {3}}}$

## meaning

The MAD is used as a measurement variable in therapy to assess and ensure organ perfusion . This is particularly important in intensive care medicine when caring for critically ill patients, e.g. B. in catecholamine therapy or sepsis . The MAD is also used to calculate the cerebral perfusion pressure (CPP) , which is used as a measure of cerebral blood flow:

${\ displaystyle {\ text {CPP}} = {\ text {MAD}} - {\ text {ICP}}}$

or

${\ displaystyle {\ text {CPP}} = {\ text {MAD}} - {\ text {CVP}}}$,

where ICP is intracranial pressure and CVP is central venous pressure . Neglecting the current air pressure conditions, the higher of the two is subtracted from the mean arterial pressure.

## determination

• Invasive measurement : The direct determination of the mean pressure by invasive blood pressure measurement is the most precise method. For this, the mean value of the measured arterial pressure curve is calculated. This method is mainly used in intensive care medicine and for intraoperative blood pressure measurement.
• Oscillometric measurement technology : This method is used in automatic blood pressure monitors. To do this, the cuff pressure is released at set intervals. In the area between systolic and diastolic pressure, the vessel wall oscillates (oscillation), which is transmitted to the cuff. The oscillations reach their maximum at the cuff pressure, which corresponds to the mean arterial pressure. The oscillation maximum and thus the MAD can be determined with far greater accuracy than the end of the oscillation, which corresponds to the diastolic pressure.
• Auscultatory measurement according to Riva-Rocci : During manual blood pressure measurement, the above-mentioned oscillations are perceived by the examiner as a Korotkow sound . This enables the systolic and diastolic blood pressure values ​​to be determined.

The MAD is also very much influenced by the degree of filling of the vessels and the relationship to the diastolic and systolic arterial pressure fluctuates in the same patient. It is therefore important to distinguish whether the MAD is actually the integral of the arterial pressure over time or whether it is only an approximate pressure calculated from the measured systolic and diastolic values.