A 68-year-old man presents for evaluation of progressive dyspnea. He has an extensive smoking history. Pulmonary function testing is consistent with severe airway obstruction. Resting arterial blood gas analysis demonstrates a partial pressure of oxygen of 54 m m H g . An echocardiogram shows normal left ventricular systolic function, right ventricular hypertrophy and dilation, and an elevated estimated pulmonary artery systolic pressure. Which of the following therapies would improve outcomes in this patient? A. Digoxin B. Oxygen C. Beta-adrenergic agonists D. Theophylline E. Bosentan
