This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'In an emphysematous patient with bullous leison which is the best investigation to measure lung volumes? \nSelect and explain. \nA. Body plethysmography, B. Helium dilution, C. Trans diaphragmatic pressure, D. DLco', 'role': 'user'}, {'content': "Answer: A \nExplanation: RV ,FRC,TLC cannot measured by spirometry. This are measured by using the helium dilution technique/ body plethysmographY. In patients with severe COPD,and with large bullae in paicular,body plethysmography is preferred because the use of helium may underestimate lung volumes. Reference:Davidson's Medicine -22nd edition,page no:675", 'role': 'assistant'}]