Mr. T is a 64 year-old man with coronary artery disease, benign prostatic hyperplasia and urinary incontinence, who presents to the Pulmonary clinic at Kashlak with shortness of breath. He has had a cough with mucus production for the last several years that occasionally worsens when he has a cold. He is currently smoking, but is cutting back, admitting to an 80 pack-year history. He has been hospitalized for “asthma” 3 times in the last year, and treated with antibiotics. He is able to walk two blocks before becoming short of breath. His resting O2 saturation is 93%. He has an albuterol inhaler that he uses once a day. Of the following, what is the most appropriate diagnostic adjunct to obtain after completing a thorough history and physical exam? *
