Scientific Reports | 2021
Effect of nocturnal oxygen therapy on exercise performance of COPD patients at 2048 m: data from a randomized clinical trial
Abstract
This trial evaluates whether nocturnal oxygen therapy (NOT) during a stay at 2048 m improves altitude-induced exercise intolerance in lowlanders with chronic obstructive pulmonary disease (COPD). 32 lowlanders with moderate to severe COPD, mean\u2009±\u2009SD forced expiratory volume in the first second of expiration (FEV1) 54\u2009±\u200913% predicted, stayed for 2 days at 2048 m twice, once with NOT, once with placebo according to a randomized, crossover trial with a 2-week washout period at\u2009<\u2009800 m in-between. Semi-supine, constant-load cycle exercise to exhaustion at 60% of maximal work-rate was performed at 490 m and after the first night at 2048 m. Endurance time was the primary outcome. Additional outcomes were cerebral tissue oxygenation (CTO), arterial blood gases and breath-by-breath measurements (http://www.ClinicalTrials.gov NCT02150590). Mean\u2009±\u2009SE endurance time at 490 m was 602\u2009±\u200965 s, at 2048 m after placebo 345\u2009±\u200962 s and at 2048 m after NOT 293\u2009±\u200960 s, respectively (P\u2009<\u20090.001 vs. 490 m). Mean difference (95%CI) NOT versus placebo was −\u200952 s (−\u2009174 to 70), P\u2009=\u20090.401. End-exercise pulse oximetry (SpO2), CTO and minute ventilation (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\\text{V}}}_{{\\text{E}}}$$\\end{document}V˙E) at 490 m were: SpO2 92\u2009±\u20091%, CTO 65\u2009±\u20091%, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\\text{V}}}_{{\\text{E}}}$$\\end{document}V˙E 37.7\u2009±\u20092.0 L/min; at 2048 m with placebo: SpO2 85\u2009±\u20091%, CTO 61\u2009±\u20091%, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\\text{V}}}_{{\\text{E}}}$$\\end{document}V˙E 40.6\u2009±\u20092.0 L/min and with NOT: SpO2 84\u2009±\u20091%; CTO 61\u2009±\u20091%; \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\\text{V}}}_{{\\text{E}}}$$\\end{document}V˙E 40.6\u2009±\u20092.0 L/min (P\u2009<\u20090.05, SpO2, CTO at 2048 m with placebo vs. 490 m; P\u2009=\u2009NS, NOT vs. placebo). Altitude-related hypoxemia and cerebral hypoxia impaired exercise endurance in patients with moderate to severe COPD and were not prevented by NOT.