This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
[{'content': 'A 62-year-old man with a 40-pack/year history of smoking presents with increased sputum production and marked SOB. On examination, he is using accessory muscles of respiration, and breath sounds are diminished with expiratory wheezes. Your clinical diagnosis is chronic obstructive pulmonary disease (COPD) exacerbationFor the above patients, select the characteristic arterial pulse finding. \nSelect and explain. \nA. pulsus tardus, B. pulsus paradoxus, C. hyperkinetic pulse, D. bisferiens pulse', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pulsus paradoxus, a drop of > 10 mm Hg in systolic blood pressure during inspiration, is caused by pericardial tamponade, airway obstruction, or superior vena cava obstruction. At times, the peripheral pulse may disappear completely during inspiration.', 'role': 'assistant'}]