Use of supplemental oxygen in patients with pulmonary arterial hypertension in REVEAL

Background: Supplemental low-flow oxygen is recommended by treatment guidelines as supportive therapy for patients with pulmonary arterial hypertension (PAH), based largely on expert opinion. Reduced diffusing capacity of lung carbon monoxide (DLCO) is associated with increased mortality in PAH. Reduced DLCO is also associated with relative hypoxemia, making the effects of supplemental oxygen use of particular interest in this sub-population. Methods: Patients in the Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL), a 5-year observational study of Group 1 PAH, were categorized by presence or absence of supplemental oxygen use and by degree of DLCO reduction. Kaplan–Meier survival estimates were calculated by group. Results: Of 3,046 patients, 57% used supplemental oxygen and 43% did not. Supplemental oxygen users had worse prognostic factors and more PAH-specific medication use. Of the 424 patients with severe DLCO reduction (<40% of predicted), 76% used oxygen and 24% did not. Patients with severe DLCO reduction who used supplemental oxygen had a significantly lower risk of all-cause mortality than those who did not (hazard ratio 0.56; 95% confidence interval 0.39 to 0.83; p = 0.0033). This was true for newly diagnosed and previously diagnosed patients. There was no relationship between oxygen use and outcomes in patients with no, mild, or moderate DLCO reduction. Conclusions: In this observational study, the risk of death was significantly lower for patients with severe DLCO reduction who received supplemental oxygen compared with those who did not. A randomized trial is warranted to further investigate the relationship between supplemental oxygen use and outcomes in PAH.