A 67-year-old man presents with a recent onset of breathlessness and cough. He has been smoking 15 cigarettes a day for the past 35 years. He thinks he may have developed asthma.

Listening to his chest, you hear a few widespread fine crackles. You refer him for a spirometry measurement, it shows the following: FEV1 = 1.7; FVC = 2.06; FEV1/FVC ratio = 0.83.