LOS ANGELES – Pulmonary arterial hypertension (PAH) patients with severely impaired diffusing capacity of the lung for carbon monoxide (DLCO) were much more likely to survive when they received home oxygen therapy, according to a disease registry analysis.
“We all know that supplemental oxygen is widely used with PAH,” said Harrison W. Farber, MD, director of the pulmonary hypertension center at Boston University. But there are practically no data showing that it is successful, and there are even fewer data for patients with PAH who have very low diffusion capacity, he added.
That knowledge gap prompted Dr. Farber and his colleagues to analyze data from the Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL), the largest disease registry in the world of patients with PAH.
“Patients in that group – the severe DLCO group – who got oxygen had poorer prognostic features but improved overall survival relative to those who didn’t,” Dr. Farber explained during a presentation at the annual meeting of the American College of Chest Physicians. “Based on this, it makes us think that home oxygen, supplemental oxygen treatment, is associated with improved survival in patients, especially those with severe DLCO and PAH.”
The 3,046 patients analyzed by Dr. Farber and his colleagues had World Health Organization Group 1 PAH with right heart catheterization hemodynamic criteria: a mean pulmonary artery pressure greater than 25 mm Hg, a pulmonary capillary wedge pressure less than or equal to 15 mm Hg, and a pulmonary vascular resistance of at least 3 Wood units (WU). Patients were at least 18 years of age and grouped by oxygen use, which was defined as any use at any time from study enrollment to the end of follow-up, and by DLCO group.
A total of 57% of the patients (1,734) received oxygen, and the remaining 43% of the patients (1,312) did not receive oxygen. Among the patients who received oxygen, 71% (1,227) received the therapy continuously, and 24% (408) received oxygen at night only.
The 424 patients with a DLCO of less than 40% were considered to have a severe DLCO impairment. The other two groups comprised 505 patients with a moderate DLCO impairment (at least 40%, but less than 60%) and 844 patients with a mild to normal DLCO (at least 60%). The DLCOs of 1,273 patients analyzed were unknown.
Among those patients with severe DLCO impairment, the risk of death was significantly lower in those who received oxygen, compared with those who did not receive oxygen (hazard ratio, 0.56; P = .0033). Oxygen use was associated with significant improvements in overall survival in both the newly diagnosed (HR, 0.47; P = .029) and previously diagnosed (HR, 0.59; P = .026) severe DLCO cohorts, Dr. Farber said.
Patients receiving oxygen were more likely to be treated with PAH-specific medications, regardless of their DLCO group.
Among the analysis’s limitations was that the lengths of time patients had been undergoing oxygen treatment were unknown. That prevented adjustments for duration of oxygen treatment, according to Dr. Farber.
Dr. Farber disclosed serving on the steering committees or advisory boards for Actelion, Bayer, Bellerophon, Gilead, and United Therapeutics. He has received research support from Actelion, Gilead, and United Therapeutics, and has been a speaker for Actelion, Bayer, and Gilead.