What is the formula for Central Perfusion Pressure (CPP)?

What is the formula for Central Perfusion Pressure (CPP)?

• A. CPP = MAP - ICP
• B. CPP = MAP / ICP
• C. CPP = ICP - MAP
• D. CPP = MAP + ICP

Answer: (A)

Central Perfusion Pressure is the pressure gradient that drives blood flow to the brain. It is defined as the difference between mean arterial pressure and intracranial pressure: CPP = MAP − ICP. This relationship shows why both rising ICP and falling MAP reduce cerebral perfusion. For example, with a MAP of 90 mmHg and an ICP of 15 mmHg, CPP is 75 mmHg, which is generally adequate. If ICP increases to 25 mmHg while MAP stays the same, CPP drops to 65 mmHg, signaling potential risk and a need for intervention. The other forms (dividing MAP by ICP, subtracting MAP from ICP, or adding the two pressures) do not represent the driving pressure for cerebral blood flow, since CPP is a pressure difference, not a ratio or sum.

Central Perfusion Pressure is the pressure gradient that drives blood flow to the brain. It is defined as the difference between mean arterial pressure and intracranial pressure: CPP = MAP − ICP. This relationship shows why both rising ICP and falling MAP reduce cerebral perfusion. For example, with a MAP of 90 mmHg and an ICP of 15 mmHg, CPP is 75 mmHg, which is generally adequate. If ICP increases to 25 mmHg while MAP stays the same, CPP drops to 65 mmHg, signaling potential risk and a need for intervention. The other forms (dividing MAP by ICP, subtracting MAP from ICP, or adding the two pressures) do not represent the driving pressure for cerebral blood flow, since CPP is a pressure difference, not a ratio or sum.