A 68-year-old man comes to the clinic with a six-month history of shortness of breath, intermittent wheezing, and coughing with sputum production. He has had difficulty walking up slight inclines for the past 4 months. He has a past medical history of hypertension and hyperlipidemia, and currently takes only amlodipine for his hypertension. He is a former smoker with a 30 pack-year history. He has never been hospitalized. His temperature is 36.9^o C (98.4^o F), pulse is 80/min, respirations are 20/min, and blood pressure is 140/82 mm Hg. Pulse oximetry on room air is 95%. His BMI is 28 kg/m2. Chest X-ray shows hyperinflation of the lungs and a spirometry shows a post-bronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) < 0.53 and FEV1 55% predicted. Which of the following is the most appropriate next step in his management?