Effect of supplemental oxygen therapy on six-minute walk distance in patients with pulmonary arterial hypertension living at 2850m: a randomized, crossover trial

Background Patients with pulmonary arterial hypertension (PAH), who permanently live at high altitude (>2500 m) face particular challenges due to hypobaric hypoxia, which may exacerbate pulmonary hypertension and impair exercise capacity .We therefore investigated the effect of low-dose supplemental oxygen therapy (SOT) on 6-minute walk distance (6MWD) in high altitude residents diagnosed with PAH. Methods Adults diagnosed with PAH, who permanently live >2500 m performed two 6MWD tests, once with SOT (1–2 l·min −1 via nasal cannula provided by a portable back-packed concentrator) and once while breathing ambient air (air) at 2850 m according to a randomized-controlled, cross-over trial. The primary outcome was the difference in 6MWD between SOT and air. Secondary outcomes were effects of SOT on heart rate, blood pressure and peripheral oxygen saturation (SpO 2 ) and Borg scale. Results 28 patients (86% women, mean± sd age 45±12 years, resting SpO 2 93±3%, mPAP 52±16 mmHg, 6MWD at 2850 m 462±100 m) were included. SOT compared to hypoxic air at 2850 m did not improve 6MWD (mean difference −5 m, CI 95%: −24 to 14 m, p=0.576), dyspnea, leg discomfort or end-exercise SpO 2 , but did increase resting SpO 2 . Conclusion In high altitude residents diagnosed with PAH, low-dose SOT as commonly prescribed via protable concentrator did not improve 6MWD nor dyspnea perception, most likely due to insufficient flow provided by the concentrator during exercise, further lowered by exertional mouth breathing and the weight of the backpacked concentrator.