A 67-year-old man comes to your clinic for his annual appointmentconcerned

A 67-year-old man comes to your clinic for his annual appointmentconcerned about increasing shortness of breath. A yearago he was able to walk up the stairs to his apartment withoutdifficulty, but now he has a hard time walking one block.He has a 70 pack-year smoking history, and several previousattempts to stop smoking have been unsuccessful.ADDITIONAL HISTORYThis patient has had slowly progressive dyspnea with exercisebut no symptoms at rest. The chronicity of the patient’ssymptoms and his ability to engage in conversation reassureyou that he does not require urgent intervention. Heexpresses frustration that he is unable to get a full breathwhen simply walking around his home. The dyspnea often worsens when he has a “cold,” but he denies an acuteincrease in symptoms. There are no other triggers. Whenyou ask about related symptoms, he describes a persistentcough productive of thick green sputum. The cough hasbeen an irritating presence for the past several months. Hedenies fevers, chest pain, chest tightness, or orthopnea.
Question: What is the most likelydiagnosis?A. AsthmaB. Chronic obstructive pulmonary diseaseC. Congestive heart failureD. Pneumonia