Fig. 2

Study procedures and measurements. Stable patients with COPD GOLD IV (n = 77) successively received conventional oxygen therapy (COT) and nasal high-flow oxygen therapy (HFOT), each for 60 min and separated by a 30 min washout phase. Blood gas and vital signs were analysed at the screening visit, at baseline, after oxygen adaption (PaO₂ > 60 mmHg or increased by ≥10 mmHg when compared to baseline), and at the end of each treatment. Bodyplethysmography, spirometry and DLCO measurements were performed at the screening visit, at baseline, and at the end of each 1-h treatment session