Patients Comfort During Highflow Oxygen Therapy With Asymmetrical Prongs: The Comfoxy-1 Trial

Background. High-flow nasal cannula (HFNC) is a promising respiratory support modality that improves oxygenation, alveolar recruitment, and comfort while reducing dead space compared to conventional oxygen therapy. Recently, a novel asymmetrical HFNC interface (Optiflow® Duet system; Fisher & Paykel Healthcare, New Zealand) has been introduced, but its physiological effects are not clear. This study aimed to investigate whether different configurations of the asymmetrical HFNC interface—specifically, fully versus partially occlusive nasal prong—affect patient comfort, dyspnea, lung aeration, ventilatory efficiency, gas exchange, and hemodynamic parameters. Methods. This was a randomized crossover physiological pilot study including 40 adults admitted to the Intensive Care Unit of Padua University Hospital for acute hypoxemic respiratory failure. Each patient received oxygen therapy with fully and partially occlusive nasal configurations in randomized order (60 minutes each, with a 10-minute washout between phases). Primary outcomes included comfort (Numeric Rating Scale, NRS) and dyspnea (Borg scale); secondary outcomes were lung aeration (assessed by electrical impedance tomography [EIT]), ventilatory efficiency (measured by corrected minute ventilation [MV] and ventilatory ratio), gas exchange, and hemodynamic variables. Comparisons between the two configurations were conducted both in the overall population and in predefined subgroups, according to baseline respiratory rates (< or ≥ 24 breaths per minute). Results. No significant differences were observed between fully and partially occlusive nostril setups in terms of comfort, dyspnea, EIT-derived measurements, gas exchange, or hemodynamic parameters, both in the overall population and in the subgroups. However, in patients with a baseline respiratory rate < 24 breaths/min, the fully occlusive nasal prong setup was associated with a modest increase in corrected minute ventilation (13 [10–16] vs. 11 [8–12], p = 0.02) and ventilatory ratio (0.0023 [0.0017–0.0027] vs. 0.0018 [0.0015–0.0020], p = 0.04). Conclusions. The degree of nasal occlusion in asymmetrical HFNCs did not significantly influence comfort, dyspnea, lung aeration, gas exchange, or hemodynamic parameters. A slight increase in ventilatory load was observed with the fully occlusive configuration in ICU patients with lower baseline respiratory rates, although the clinical relevance of this finding remains uncertain. CLINICAL TRIAL NUMBER: ClinicalTrial.gov registration number NCT06778291 (01/07/2025) NEW & NOTEWORTHY The degree of nasal occlusion in asymmetrical HFNCs (Optiflow® Duet system; Fisher & Paykel, Healthcare, Auckland, New Zealand) did not significantly influence comfort, dyspnea, lung aeration, gas exchange or hemodynamic variables. A slight increase in ventilatory load was observed with the fully occlusive setup in patients with lower baseline respiratory rates, although the clinical significance remains uncertain.