BACKGROUND: High-flow nasal oxygen (HFNO) therapy delivers humidified, heated air with flow rates of up to 60 L/min with oxygen entrained. HFNO has advantages over conventional oxygen therapy, including precise and reliable fraction of inspired oxygen delivery, therefore is recommended as first-line treatment for people with acute hypoxaemic respiratory failure. OBJECTIVES: This pilot study aimed to determine the feasibility and acceptability of domiciliary nasal high flow (NHF) without entrained oxygen for people with chronic obstructive pulmonary disease (COPD) and severe breathlessness. DESIGN: Single-arm, mixed-methods, pilot study of an 8-day, air-only NHF intervention in adults with COPD and severe breathlessness not requiring domiciliary oxygen therapy. METHODS: Participants were educated and advised to use NHF for ⩾7 h per night for 7 nights with day use as desired. Patient-reported outcome measures were assessed on Days 3, 5 and 8. PRIMARY OUTCOME: feasibility. SECONDARY OUTCOMES: breathlessness (dyspnoea), fatigue, quality of life, physical function, sleep, tolerability and safety. Acceptability was also assessed through semi-structured interviews. RESULTS: Fifteen participants were enrolled (mean age 73.6
40% women
mean FEV CONCLUSION: Domiciliary NHF was a feasible intervention, albeit with varied adoption and acceptability. These trial implementation outcomes may have affected preliminary effectiveness outcomes. Further research is required to determine what role domiciliary NHF may have for people with COPD and severe breathlessness. TRIAL REGISTRATION: ACTRN12621000044820.