A 55-year-old man comes to the physician because of a 4-month history of worsening shortness of breath. He has a 5-year history of COPD. He smoked two packs of cigarettes daily for 40 years but quit three years ago. Vitals are within normal limits. Arterial blood gas shows:
pH 7.40
PCO2 43 mm Hg
PO2 75 mm Hg
Which of the following is the most appropriate next step in management?
Bosentan
Fluticasone
Home oxygen therapy
Ipratropium
Nedocromil
