How to Calculate Mean Arterial Pressure

Mean arterial pressure (MAP) is a function of systolic and diastolic blood pressure.
The easiest way to calculate MAP is to get the pulse pressure (Systolic BP – Diastolic BP), then multiply the result with 1/3. The answer you get, add it to diastolic pressure and the result is the MAP.

1/3(SBP-DBP)+DBP = MAP
Explanation.
Systole is the time when the ventricles are contracting and diastole is the relaxation time. In normal condition, the systole phase takes about half the time the diastole takes. In other words, diastole takes twice as longer as systole.
This explains why we cannot just add systolic blood pressure and diastolic blood pressure and divide it with 2. The time each takes is different. In-stead, if we divided the time in equal parts, we would have 3 equal parts, where the systole takes 1/3 and diastole takes 2/3 of total time.

To test if this is true, we can multiply systolic BP by 1/3 and diastolic BP by 2/3 and add the results together to come up with the mean arterial pressure.

Lets use real example using the known formula of 1/3(SBP-DBP)+DBP = MAP and control theoretical explanation and see if we will come up with the same results.
Lets say a patient BP = 120/60. Pulse pressure (SBP-DBP) would be 120-60 = 60.
Mean Arterial Formula: 1/3(SBP-DBP)+DBP = MAP
1/3 X 60 = 20
Add the result above to DBP (60)
20+60 = 80
Lets now use the theoretical way of testing if the formula above gives a true picture of how the heart works in normal conditions.
Our sample BP is 120/60

We will multiple SBP X 1/3 AND DBP X 2/3 and then add the total. We should get the same results as above
1/3×120 = 40 + 2/3×60 = 40. 40+40 = 80
:-)
Happy? Leave your comments/complements

Comments

  1. Cool, I knew the formula but this explains the theory behind it so clearly.

  2. its gud

  3. Dr Awais Ahmed says:

    its very nice way to clear the concept regarding mean arterial pressure but do any body know what is the mechanism of mean arterial pressure checking in the monitors used in critical care like philips or hewlett packard. please let me know how they calculate even with nibp cuff they give mean pressure.

  4. Excellent explanation, will use it to explain this phenomenon to my class.

  5. Does diastole always take twice the time as systole REGARDLESS of heart rate? MAP is calculated the same way in human and cat. In a cat with heart rate of 160 and pressure of 120/60 and a human with heart rate of 70 and pressure of 120/60, do they have the same MAP?

  6. According to the article and the information given that MAP is calculated the same way for both humans and cats, I would say both the human and the cat have the same MAP, as the heart rate is not figured into the equation. The next question would be, does a MAP of 80 have the same indications for a cat as it does for a human?

  7. nice one……..

  8. Judy, RN says:

    Interesting site, I like it. I am a senior nurse that learned the formula as : systolic + diastolic x 2
    —————————-
    3
    = mean arterial pressure
    You did have good answer behind the formula, sometimes we as nurses are told to learn a formula, but do not receive the theory behind it. I makes so much sense to learn both at once.