This will be a randomized, cross-over trial evaluating the efficacy of nasal HFOT vs. LFOT on cycling endurance in patients with COPD. Each patient will perform two constant load cycling exercise tests to exhaustion using HFOT and LFOT on two consecutive days, respectively, according to randomization. The load of the cycle ergometer will be set at 75% of the individually estimated maximum work rate (Wmax). During exercise tests, LFOT will be provided by a standard nasal cannula at a flow rate of 3 L/min using an oxygen concentrator. HFOT will be applied by a dedicated large bore nasal cannula at a flow rate 60 L/min, FiO2 45%, temperature 32 °C, using a HFOT device.
