Q. A 55-year-old male presents to his physician’s office with progressively increasing episodes of shortness of breath starting approximately six (6) months ago. The patient admits to smoking a pack of cigarettes daily for 15 years, but states he quit approximately eight (8) years ago when he developed a cough. The cough has been on-and-off since, but the patient admits to a productive cough of white sputum for the past two (2) years. He attributed this to his history of smoking and thought nothing of it until his recent bouts of SOB. The patient is in mild respiratory distress with a barrel chest, pursed lip breathing, and is using accessory respiration muscles. Upon auscultation, breath sounds are distant, and crackles are present bilaterally in the lower lung fields. Spirometry shows: decreased FEV1:FVC ratio, increased residual volume, and decreased diffusion capacity. Chest X shows hyperinflation with hypertranslucency of the lower lobes bilaterally. Which of the following is the most likely diagnosis?