Physiological effects of nasal high flow therapy during exercise in patients with chronic obstructive pulmonary...

Nasal high flow (NHF) has been proposed to sustain high intensity exercise in people with COPD, but we have a poor understanding of its physiological effects in this clinical setting.

What is the effect of NHF during exercise on dynamic respiratory muscle function and activation, cardiorespiratory parameters, endurance capacity, dyspnoea and leg fatigue as compared to control intervention.

Randomized single-blind crossover trial including COPD patients. Two constant workload exercise testing were performed at 75% of peak power with NHF (30L/min, 34°C) or with control intervention. Pressure time product of the transdiaphragmatic pressure (PTPdi/min) and other physiological measurements were continuously monitored. Dyspnoea and lower limb fatigue were assessed using the 10-Borg scale.

14 patients with severe obstruction (median FEV1: 40 (IQR 28 to 52) %) were included. Their median age was 70 (IQR 57 to 72) years. At isotime, NHF had little to no effect on PTPdi/min (MD -15cmH2O.s/min, 95% CI -62 to 33) but increased tidal volume (MD 77mL, 95% CI 21 to 133). NHF also improved endurance capacity (MD 20s, 95% CI 2 to 40) and dyspnoea at isotime (MD -1.1, 95% CI -2.1 to -0.1). NHF had no or uncertain effect on other outcomes.

NHF has little to no effect on dynamic respiratory muscle function and activation but improves Vt. It leads to a trivially small increase in endurance capacity but a worthwhile improvement in dyspnoea. NHF may be beneficial for individuals experiencing critical inspiratory constraints and significant dyspnoea.