A 67-year-old man presents with a history of dyspnea, which has progressed for the past several years. He began smoking cigarettes at 15 years of age and continues to smoke one pack per day. Worsening breathlessness forced him to retire as a laborer, and he has sought emergency care for what he calls bronchitis twice in the past year. His physical examination is notable for diminished breath sounds on auscultation, with a prolonged expiratory phase. Spirometry reveals severe airflow obstruction (ratio of forced expiratory volume in 1 second [FEV1] to forced vital capacity [FVC], 0.43; FEV 1, 34% of the predicted value). How should this case be managed?