COPD USMLE Step 1 Practice Question
A 59 year old man has progressive exertional dyspnea and dry cough for 1 year. He worked in construction and now has bibasilar end inspiratory crackles. Pulmonary function testing shows reduced total lung capacity and reduced diffusion capacity for carbon monoxide. During exercise, his oxygen saturation drops significantly. Which of the following is the most likely cause of his exercise induced hypoxemia?
Answer choices
- AIncreased airway resistance due to bronchial smooth muscle contraction
- BLoss of central respiratory drive due to medullary depression
- CRight to left intracardiac shunting through a patent foramen ovale
- DDestruction of alveolar walls causing increased compliance
- EThickening of the alveolar membrane that limits diffusionCorrect answer
- FMismatch of ventilation to perfusion causing areas of low V/Q ratio
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