Purpose: Nasal high flow (NHF) is increasingly used in COPD patients with chronic respiratory failure. An asymmetrical cannula interface (AI) may enhance these benefits by combining increased airway pressure with reduced rebreathing from anatomical dead space. The aim of this study was to compare the effects of NHF using an AI versus a conventional symmetrical interface (SI) on tidal volume (Vt), respiratory rate (RR), minute ventilation (MV), gas exchange, and neuro-respiratory drive (NRD). Methods: Following a 15-minute baseline period, COPD patients recovering from acute exacerbation underwent two randomized 45-minute sessions of NHF therapy using either the AI or SI. All sessions were conducted during daytime in a semi-recumbent position. Ventilation was recorded using calibrated respiratory inductance plethysmography, and transcutaneous CO 2 (TcCO 2 ) and oxygen saturation (SpO 2 ) were continuously monitored. In addition, intercostal surface electromyography (sEMG) of the parasternal muscles was performed to assess NRD. Results: In a group of 18 patients NHF significantly reduced RR and TcCO 2 , regardless of the interface used. AI significantly reduced MV compared with both baseline and SI (p = 0.048), while SpO 2 increased. sEMG activity increased compared with baseline without a corresponding rise in tidal volume; however, no difference was observed between the two interfaces. Conclusion: NHF reduced RR by shortening both inspiratory and expiratory times without altering the duty cycle. The lower MV during NHF with AI, accompanied by higher SpO 2 , may indicate improved gas exchange efficiency. The use of AI could enhance the respiratory support effects of NHF in patients with advanced COPD. Keywords: nasal high flow, COPD, minute ventilation, gas exchange, work of breathing
Nilius et al. (Sun,) studied this question.