A 68-yeаr-оld mаle pаtient presents tо the Primary Care оffice with a 10-month history of persistent non-productive cough and difficulty breathing with mild exertion. PMH is significant for hypertension and diabetes. Current medications include enalapril and metformin. He smoked 1 pack of cigarettes per day for 25 years, but he quit 6 months ago. Vital signs are stable. Pulse oximetry on room air is 87%. Physical examination reveals grade 3 digital clubbing. Chest auscultation reveals bibasilar inspiratory crackles. CT scan shows predominant basilar opacities associated with honeycombing. The diffusing capacity of the lung (DLCO) is reduced.Which of the following interventions is most appropriate for this patient?