In the medical world, a person's systolic blood pressure is the pressure in the arteries when the heart beats, while diastolic blood pressure is the blood pressure during the "rest" interval between heartbeats. While both are important, and independent of each other, they are also important in determining the "average" blood pressure for certain uses (such as determining how well blood is flowing to an organ). This value, called the mean arterial pressure (MAP) can be calculated easily using the equation MAP = (2(DBP) + SBP)/3, with DBP = diastolic pressure or diastolic blood pressure, and SBP = systolic pressure or systolic blood pressure.
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Part 1 of 3: Using the MAP Formula
Step 1. Measure your blood pressure
To be able to calculate mean arterial blood pressure (MAP), you need to know your diastolic and systolic blood pressures. If you don't know both, then take your blood pressure to find out. While there are various sophisticated methods of measuring blood pressure, all you need to get a fairly accurate result is a manual sphygmomanometer and a stethoscope. Keep in mind, the blood pressure measured when you hear the first pulsating sound is the systolic blood pressure, and the blood pressure measured when the pulse disappears is the diastolic blood pressure.
- If you're hesitant to take your own blood pressure, read the section below for a step-by-step how-to guide, or read our dedicated article.
- Another option is to use an automatic blood pressure monitor which you can use for free at many pharmacies and supermarkets.
Step 2. Use the formula MAP = (2(DBP) + SBP)/3
Once you know your diastolic and systolic blood pressure, calculating your MAP is easy. Just multiply your diastolic pressure by 2, add it to your systolic pressure, and divide the number by 3. This calculation is basically the same as the formula for finding the mean (mean) of several numbers. MAP is expressed in mm Hg (or "millimeters of mercury"), a standard measure of pressure.
- Remember that diastolic pressure must be doubled because the cardiac system spends about two-thirds of its time "resting" in the diastole phase.
- For example, let's say you take a blood pressure measurement and find your diastolic pressure of 87 and systolic of 120. Next, plug the two values into the equation, and solve like this: MAP = (2(87) + 120)/3 = (294)/ 3 = 98 mm Hg.
Step 3. Alternatively, use the formula MAP = 1/3(SBP – DBP) + DBP
Another way to get the MAP value is to use this simple formula. Subtract the systolic pressure by the diastolic pressure, divide by three, and increase your diastolic pressure. The result you get should be exactly the same as the one you got using the previous formula.
Using the same blood pressure example as above, we can solve this equation as follows: MAP = 1/3(120 – 87) + 87 = 1/3(33) + 87 = 11 + 87 = 98 mm Hg.
Step 4. To estimate the MAP, use the formula MAP approx = CO × SVR
In medical conditions, this formula is another way of estimating MAP. These formulas using the variable cardiac output (CO; expressed in L/min) and systemic vascular resistance (SVR; expressed in mm HG × min/L) are sometimes used to estimate a person's MAP. Although the results obtained from this formula are not always 100% accurate, this value is usually suitable for use as an approximate value. Keep in mind that CO and SVR are usually only measured using specialized equipment in medical care (although both can be determined using simpler methods).
In women, normal cardiac output is about 5 L/min. If we assume an SVR of 20 mm HG × min/L (at the upper limit of the normal value range), the woman's MAP is approximately 5 × 20 = 100 mm Hg.
Step 5. Consider using a calculator to make the calculations easier
Another thing to remember is that the MAP calculation does not have to be done manually. If you're in a hurry, there are many online calculators like this one that can help you calculate your MAP value in real time, simply by entering your blood pressure value.
Part 2 of 3: Understanding Your MAP Score
Step 1. Find a "normal" range of MAP values
As with systolic and diastolic blood pressure, there are certain ranges of MAP values that are generally considered "normal" or "healthy." Although some healthy people have MAP values outside this range, these values often signal the presence of a potentially dangerous cardiovascular condition. In general, the MAP value is between 70-110 mm Hg considered normal.
Step 2. Consult your doctor if you have dangerous MAP or blood pressure values
If you have a MAP value outside the "normal" range above, this may not necessarily mean that you are in a dangerous condition, but you should still consult your doctor for a thorough examination and analysis. The same is true for abnormal systolic and diastolic values (which should be below 120 and 80 mm Hg, respectively). Don't avoid consulting your doctor - many cardiovascular diseases are easily treatable if treated before they develop into serious problems.
Keep in mind that a MAP value below 60 is generally considered dangerous. As described above, the MAP is used to determine how well blood can reach organs - a MAP value of over 60 is usually required for adequate perfusion
Step 3. Be aware of certain medical conditions that can affect MAP
It's important to understand that certain medical conditions and medications can change what is considered a "normal" or "healthy" MAP value. In this case, your doctor may need to monitor your MAP to make sure it doesn't fall too far from an acceptable range to prevent serious problems. Below are some types of patients whose MAP values should be closely controlled. If you're not sure which conditions or medications could change your acceptable MAP range, talk to your doctor right away:
- Patients with head injuries
- Patients with certain aneurysms
- Patients experiencing septic shock and taking vasopressor drugs
- Patients taking vasodilator infusion drugs (GTN)
Part 3 of 3: Measuring Your Own Blood Pressure
Step 1. Find your pulse
If you're not sure what your systolic and diastolic blood pressure values are, taking your own blood pressure measurement is actually quite easy. All you need is a manual sphygmomanometer and a stethoscope - both should be available at your local pharmacy. Wait until your body is completely relaxed, then sit down and feel the inside of your arm or wrist until you can feel a pulse. Place the stethoscope in your ear to prepare for the next step.
If you're having trouble, try using a stethoscope to listen to your pulse. When you hear a light, regular "pulse," you've found it
Step 2. Insert the sphygmomanometer into your upper arm
Fit and secure this sheath around the biceps muscle of the same arm where you find your pulse. Most tensimeter casings have an adhesive for easy fixing. When it is firmly in place (but not tight), use the small pump on the sphygmomanometer to inflate it. Pay attention to the pressure gauge - you will need to inflate it to about 30 mm Hg higher than your estimated systolic pressure.
As you do so, hold the head of the stethoscope at the point of your pulse (or if you can't find it, at the crease of your elbow). Listen - if you have inflated the casing to sufficient pressure, you should not be able to hear your pulse at this point
Step 3. Allow the sphygmomanometer casing to deflate while keeping an eye on the pressure gauge
If air has not flowed out of the casing, do not turn the air valve (the small bolt near the pump) counterclockwise until the air flows out at a slow, steady rate. Watch the pressure gauge as air flows out of the casing - the value should decrease slowly.
Step 4. Listen to the first pulse
As soon as you hear the first pulse with your stethoscope, write down the visible pressure on the pressure gauge. This value is pressure systolic You. In other words, this is the pressure when the arteries are at their strongest right after the heart beats.
As soon as the pressure in the sphygmomanometer is equal to your systolic pressure, blood can flow under it with each heartbeat. This is the reason for using the value expressed in the pressure indicator at the first beat as the systolic pressure value
Step 5. Listen and feel the pulse disappear
Keep listening. As soon as you can no longer hear the pulse on the stethoscope, write down the pressure expressed in the gauge. This value is pressure diastolic You. in other words, this is the pressure at which the arteries "rest" between heartbeats.
As soon as the pressure in the sphygmomanometer equals your diastolic pressure, blood can flow under it even when the heart is not pumping blood. This is why you can no longer hear the pulse, and why we use the value expressed in the meter after the last beat as the diastolic pressure
Step 6. Know what can affect your blood pressure
Normal blood pressure is generally below 80 mm Hg for diastolic pressure and below 120 mm Hg for systolic pressure. If none of your blood pressures are greater than these normal values, you probably don't need to worry. Various health conditions, whether serious or not, can affect a person's blood pressure. If you experience any of these conditions, try waiting for it to subside first, then try again.
- Feeling anxious or stressed
- Just ate
- Just finished exercising
- Smoking, drinking alcohol, or drugs
- Pay attention if your blood pressure is persistently high. You should call your doctor (even if you feel fine). This can indicate hypertension (high blood pressure) or prehypertension, which can eventually develop into a serious condition.
