Clinical vignette: A 76-year-old man consults you for increasing shortness of breath over the past two years and an increasing requirement for home oxygen. A video-assisted thoracoscopic lung biopsy shows findings of usual interstitial pneumonitis, and he has no identifiable cause for pulmonary fibrosis, so he is considered to have idiopathic pulmonary fibrosis (IPF). His diffusing capacity for carbon monoxide (DLCO) is 45% of predicted, and his total lung capacity is 40% of predicted. Because of his advanced age, he is not considered a candidate for lung transplantation. What treatment should you recommend?