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
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. Instead, if we divided the time into equal parts, we would have 3 equal parts, where the systole takes 1/3 and diastole take 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.
Let’s use the 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.
Let’s 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
Let’s 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/compliments
Cool, I knew the formula but this explains the theory behind it so clearly.
Thank you Lorae for the compliments
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.
Thank you Dr Awais for your compliments. I definately will dig into the monitors but I bet they compute the Systolic Blood pressure and diastolic blood pressure and they calculate the MAP using mean aterial pressure formula we all know about. Not hard to do at all programmatically using a software
Heart monitors calculate MAP using the same formula and adding the heart rate divided by 10.
Because heart rate does play a role in the determination of MAP.
When using invasive monitoring CVP is used to calculate MAP, by adding the divided heart rate you can get closer to a true MAP.
The main thing to understand is that without central monitoring the calculated MAP is a close proximity, not 100% accurate.
Dr Igwe says
Excellent explanation, will use it to explain this phenomenon to my class.
Thank you Dr. Igwe. for your compliments
Joey Hung says
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?
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?
I didn’t know that. Good to know
domz tolentino says
Thank you for the compliments
Judy, RN says
Interesting site, I like it. I am a senior nurse that learned the formula as : systolic + diastolic x 2
= 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.
@July, my explanation kind of decodes the formula or MAP and explains how that formula was formulated. I hope you found it helpful
Within our respiratory therapy field, we use the formula (2xDBP) + SBP/ 3. And it gives you the same answer. For example: (60×2) + 120 / 3 = 240 / 3 = 80mmHg. The explanation to it is the same as one given above.
so now that we have the MAP …what is the recommended range for male in 70s ?
With the numbers above explained and how MAP is calculated, it is not so evidence based practice (EBP) to dictate a mean aterial pressure based on age. So many factors come to play and that is why we only deal with a minimum mean aterial pressure of 60mm/Hg.
@Bimu, thank you for your input about MAP calculation formula. Please note that this explanation on how to calculate mean aterial pressure is only explaining how the MAP formula was derived at
Mahima Jamwal says
Thnkewww so much to explain it in this simple way…??
I am glad you found it helpful Jamwal. Thank you for stopping by
Excellent explanation not explained as such in textbooks. They give it more as like a memorize it thing.
mohamed gad ibrahim says
first time to understanding it
I want to know how is the normal blood pressure (magical figure of 120/80) is arrived, by which method?
Automatic BP monitors do not use the formula above to calculate MAP. If you try the formula on the numbers displayed by the monitor they may not add up. In fact most of the monitors estimate BP based on the so called oscillometric method. When you measure BP using manual sphigmomanometer and open the valve to gradually deflate cuff the needle of the manometer will go smoothly down until you hear the first Korotkoff sound. At this point the needle will go down but oscillating (jerking) with each sound. As the needle goes down the amplitude of this tiny oscillations increases then reaches the maximum, decreases and disappears. The cuff pressure at which the amplitude of this oscillations is maximum is the MAP. It is difficult–although not impossible–for us to by looking at the manometer needle, determin when the amplitude of the oscillations is maximum. For machine it is relatively easy task. BP monitors first calculate MAP and then based on amplitudes before MAP determine SBP and based on amplitudes after MAP calculate DBP. It is fun to try to figure MAP using manual sphigmomanometer.
scared edabilo says
? so cofused? why so hard