Background: High-flow oxygen therapy (HFOT) provides oxygen-enriched, humidified, heated air at high flow rates. It could be an alternative to low-flow oxygen therapy via nasal cannula (LFOT), which is commonly used by patients with chronic obstructive pulmonary disease (COPD) during endurance training in pulmonary rehabilitation. We hypothesized that HFOT improves exercise endurance in COPD patients compared to LFOT. Methods: Patients with stable, moderate to severe COPD with resting pulse oximetry (SpO2) ≥92% performed two cycle constant work-rate exercise tests to exhaustion at 75% of their maximum work-rate on two different days, using first LFOT (3L/min), then HFOT (60L/min, FiO2 0.45), or vice versa, according to a randomized, crossover design. The primary outcome was the difference in endurance time between therapies. Secondary outcomes were respiratory rate, SpO2, heart rate, arterial blood gases and dyspnea. Results: 79 patients, mean±SD aged 58±9years, FEV1 63±9%predicted were randomized and included in the intention-to-treat analysis. Endurance time improved under HFOT versus LFOT by a mean of 85s (95%CI: 7 to 164), corresponding to an increase of 13% (95%CI: 1 to 28). Under HFOT, patients had lower respiratory rate and higher SpO2 at isotime; at end-exercise under HFOT, SpO2 remained higher, 1.9% (1.5 to 2.3), and dyspnea sensation was lower, -0.8 points Borg CR10-scale (-1.2 to -0.3), compared to LFOT. Conclusions: HFOT improved endurance time in patients with stable, moderate to severe COPD by improving arterial oxygenation, respiratory rate and dyspnea compared to LFOT. Therefore, HFOT is promising for enhancing exercise performance in COPD. (ClinicalTrials.gov, NCT03955770)
