A 57-year-old man who has not seen a physician in 8 years comes to your office as a new patient. He says he has increased shortness of breath walking up stairs and a chronic nonproductive cough. He says he has no chest pain, weight loss, or hemoptysis. He has smoked 3/4 of a pack of cigarettes daily for 40 years (a 30 pack-year history).

His vital signs are normal. Pulse oxygen is 94% on room air. His physical examination is unremarkable. You suspect he may have chronic obstructive pulmonary disease (COPD) and order pulmonary function testing (PFT).