Effect of short-term supplemental oxygen therapy on six-minute walk distance in highlanders at risk for pulmonary hypertension: a randomized, crossover trial

Background Little is known about the effects of portable supplemental oxygen therapy (SOT) to improve exercise performance in highlanders at risk for high altitude pulmonary hypertension (HAPH). We aimed to investigate whether SOT improves six-minute walk distance (6MWD) and reduces perceived dyspnea in highlanders at risk for HAPH. Methods In a pragmatic randomized open-label crossover trial, adult highlanders, living >2500 m, with a peak tricuspid regurgitation velocity >2.8 m·s −1 corresponding to a tricuspid regurgitation pressure gradient ≥31 mmHg by echocardiography were included. Highlanders were randomized to perform two 6MWD tests at 3250 m with and without SOT (50 mLpulse volume, via nasal cannula, provided by portable device). The primary outcome was the effect of SOT on the 6MWD compared to ambient air (air). Secondary outcomes were vital parameters and dyspnea assessed by BORG CR10 scale with SOT versus air. Results 47 highlanders (44% male, mean± sd age of 52±12 years, TRPG 41±10 mmHg and oxygen saturation (SpO 2 ) of 88±3% were included. SOT did not improve 6MWD compared to air (457±90 m versus 475±84 m; mean difference with SOT of −18 m (95%CI, −30 to 8, p=0.241)). End-exercise dyspnea was significantly lower with SOT compared to air, along with reduced heart rate and higher SpO 2 . Conclusion In hypoxemic highlanders at risk for HAPH, portable low-dose SOT did not improve 6MWD, despite lower dyspnea perception, lower heart rates, and higher SpO 2 at end-exercise. This indicates that low-dose SOT oxygen as commonly applied in various clinical settings, does not increase 6MWD. Whether it reduces cardiovascular stress during exercise needs to be further studied.