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': 'Measurements of intravacular pressure by a pulmonary aery catheter should be done: \nSelect and explain. \nA. At end expiration, B. At peak of inspiration, C. During mid inspiration, D. During mid expiration', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (At end expiration): The changes in intrathoracic pressure that occur during different phases of respiration influence measurement of intravascular pressure. These changes are minimal at end expiration which therefore is the best phase for measurement of intravascular pressure.', 'role': 'assistant'}]