This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
When evaluating an ABG from a client with a subdural hematoma, the nurse notes the PaCO2 is 30 mm Hg. Which of the following responses best describes this result? 
Select and explain. 
A. Appropriate; lowering carbon dioxide (CO2) reduces intracranial pressure (ICP)., B. Emergent; the client is poorly oxygenated., C. Normal, D. Significant; the client has alveolar hypoventilation.
A: Appropriate; lowering carbon dioxide (CO2) reduces intracranial pressure (ICP).
Answer: A: Appropriate; lowering carbon dioxide (CO2) reduces intracranial pressure (ICP). 
Explanation: A normal PaCO2 value is 35 to 45 mm Hg. CO2 has vasodilating properties; therefore, lowering PaCO2 through hyperventilation will lower ICP caused by dilated cerebral vessels.

Option B: Oxygenation is evaluated through PaO2 and oxygen saturation.
Option D: Alveolar hypoventilation would be reflected in an increased PaCO2.