A Novel Approach to High-flow Nasal Oxygen Delivery: Physiological and Clinical Perspectives on Asymmetrical Cannulas.

High-flow nasal cannula (HFNC) therapy has become an essential therapeutic modality across a broad spectrum of indications, and it is currently regarded as the optimal initial therapeutic option for patients presenting with acute hypoxemic respiratory failure. A novel HFNC interface with an asymmetrical cannula has recently been introduced to optimize the physiological benefits of HFNC. It features prongs, one with a smaller diameter and another with a larger diameter, to enhance positive end-expiratory pressure and carbon dioxide washout. This is achieved by modulating the prong-to-nare area ratio to maintain a balance between airway pressure and dead space clearance. Recent studies have indicated that the use of an asymmetrical design may result in enhanced upper airway pressure and dead space washout. Asymmetrical cannulas may enhance patient comfort, reduce work of breathing, and lower minute ventilation. However, they do not significantly differ from standard cannulas in terms of gas exchange, oxygenation, diaphragm activity, lung compliance, dorsal fraction of ventilation, or lung impedance. Further research is needed to determine whether asymmetrical cannulas offer clinical advantages in specific patient populations, to identify optimal sizing parameters, and to assess their long-term safety and efficacy in diverse clinical settings.