MRCP2-4185

An 80-year-old woman visits her GP complaining of increasing shortness of breath for the past 4 months. She occasionally experiences a productive cough. Her medical history includes two previous heart attacks treated with percutaneous coronary intervention and hypercholesterolaemia managed with simvastatin. She has a 35 pack-year smoking history and does not consume alcohol.

The GP orders lung function tests which reveal:

Forced expiratory volume in 1 second (FEV1) 0.78L
Forced vital capacity (FVC) 1.68L
Total lung capacity 5.08L

What is the most probable diagnosis?