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
[{'content': 'Hyperventilation results in all of the following EXCEPT \nSelect and explain. \nA. increased PCO2, B. decreased cerebral blood flow, C. hypocapnia, D. increased PO2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hyperventilation is initiated due to an increase in PCO2. The increased rate of breathing "blows off" excess CO2. Thus, hyperventilation results in a decrease of PCO2 to its normal physiologic range. The increased respiratory rate causes a ↑PO2.\nThe resultant decrease in CO2 causes hypocapnia.\nThe resultant decrease in PCO2 causes vasoconstriction, leading to ↓cerebral blood flow.\nRespiratory alkalosis occurs due to the ↑pH.', 'role': 'assistant'}]