How to Calculate CPP With MAP
Cerebral perfusion pressure, or CPP, is a key metric used by health-care providers to determine the pressure of blood flowing to the brain. For adults, CPP normally ranges from 70mmHg to 90mmHg. Deviations outside this range can cause brain damage; the calculation of CPP is therefore integral to monitoring the impact of medical procedures and traumatic events on a patient's brain.Things You'll Need
- Central venous catheter
- Stethoscope
- Sphygmomanometer (blood pressure cuff)
- Calibrated transducer
Instructions
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Determine the patient's systolic and diastolic blood pressures using the sphygmomanometer. Place the cuff above the patient's elbow so that it is positioned above the brachial artery. Find the brachial pulse and place the stethoscope's drum over it. Pump up the cuff until the gauge reads 180mmHg. Release pressure until you can hear a heartbeat through the stethoscope. The pressure reading on the sphygmomanometer at that point is the systolic pressure. Continue releasing pressure until you can no longer hear the heartbeat. The reading on the sphygmomanometer at that point is the diastolic pressure.
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Calculate mean arterial pressure (MAP) by multiplying diastolic blood pressure by 2, then adding the systolic pressure and dividing the total by 3. For example, if a person has a blood pressure reading of 140/90 (high blood pressure), his MAP is: (90 * 2 + 140) / 3 = 106.67
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Measure the patient's central venous pressure using a central venous catheter. Thread the catheter through any large vein (doctors often use the internal jugular or femoral vein) until it is almost to the heart's right atrium, in the lower section of the superior vena cava. Once the catheter is positioned, connect it to a calibrated transducer to read the CVP.
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Subtract the central venous pressure from the mean arterial pressure to get the cerebral perfusion pressure. If CPP reaches levels outside the typical range of 70mmHg to 90mmHg, additional intervention may be required.
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