70 yr old male, 2012 had heart stent put in diagnosed with heart disease and a fib. 2013 had viral pneumonia. 2013 ct scan 2 view CXR noted mild right basilar infiltrate consistent with Pneumonia. 2014, began having a mild but chronic cough which worsened and a second CT scan with contrast showed marked emphysematous changes, no lung mass or lymphadenopathy, infiltrates or effusions noted. Heart demonstrates borderline cardiomegaly. Had a pulmonary function test done with no significant findings such as obstructions. Smoked for 25 yrs. stopped 1985, was in agent orange in Vietnam. What is your best bet for a diagnosis?