Supplemental oxygen on exercise performance in highlanders with pulmonary vascular disease. A pragmatic open-label crossover RCT

<bold>Introduction:</bold> Patients with pre-existing pulmonary vascular diseases (PVD) are among millions of permanent residents of high altitude (HA) places >2500m. We investigated in PVD-patients living in Quito (~2850m), Ecuador, whether portable supplemental oxygen therapy (SOT) improves six-minute walk distance (6MWD). <bold>Methods:</bold> PVD patients diagnosed with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension, were randomly allocated to perform a 6MWD test with either first SOT followed by an exercise test without intervention or vice versa, according to a pragmatic randomized, controlled, open-label crossover design. Before each test, patients rested for 10min and received the corresponding intervention (SOT or nothing). <bold>Results:</bold> 28 patients (24 women, 26 PAH, 2 CTEPH) aged 46±12y were included. Without intervention, 6MWD was, mean±SE, 462±18m and SpO2 decreased with exercise by 4.3%(95%CI,2.5;6.2) from a mean±SE 87.9±0.9% to 83.6±0.9%. Correspondingly, HR increased by 33bpm(95%CI,26;41) from 73±3bpm to 106±3bpm. Under SOT, resting SpO2 increased to 93.6±0.9%(P<0.05 vs. no intervention) but decreased by 9.0%(95%CI,7.1;10.8) with exercise to a similar SpO2-level compared to no intervention. In accordance, 6MWD remained unchanged with SOT: mean difference(95%CI) of -5m (−28;17), P=0.647. No differences in dyspnea/leg fatigue sensation were observed between interventions. <bold>Conclusion:</bold> In hypoxemic highlanders with PVD, portable SOT did not improve 6MWD. Moreover, since SOT did not reduce the exercise-associated cardiopulmonary stress nor dyspnea sensation, other SOT settings or short-term measures to improve exercise should be considered.