Progressive Care Nursing Certification (PCCN) Practice Exam

Which factor does NOT affect cerebral perfusion pressure?

1. Mean arterial pressure (MAP)

2. Intracranial pressure (ICP)

3. Heart rate

4. Oxygen consumption

The correct answer is: Heart rate

Cerebral perfusion pressure (CPP) is a critical parameter that reflects the adequacy of blood flow to the brain. It is calculated using the formula: CPP = MAP - ICP, where MAP is the mean arterial pressure and ICP is the intracranial pressure. In terms of the factors listed in the question, heart rate does not have a direct effect on cerebral perfusion pressure. While heart rate can influence cardiac output, which may eventually affect cerebral blood flow, it does not directly alter the components of the CPP calculation (MAP or ICP). Therefore, heart rate is not considered a factor affecting cerebral perfusion pressure. On the other hand, mean arterial pressure is crucial since it represents the average blood pressure in a person's arteries during one cardiac cycle; a decrease in MAP would lead to lower cerebral perfusion pressure. Intracranial pressure also directly influences CPP; an increase in ICP effectively reduces CPP, indicating compromised blood flow to the brain. Oxygen consumption is related to the metabolic needs of the brain, which can indirectly affect cerebral blood flow but does not specifically alter the equation for CPP as MAP and ICP do. Thus, heart rate is the factor that does not impact cerebral perfusion pressure directly.