High-flow nasal oxygenation: a transformative tool in airway management
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Effective high-flow nasal oxygenation (HFNO) supportive therapy involves delivering fully conditioned gas through a wide-bore nasal cannula at very high-flow rates (up to 60 L/min) and maintaining a constant oxygen concentration ranging from 21% to 100% [1,2]. Although the exact mechanisms of action and physiological effects are not entirely understood, HFNO may enhance carbon dioxide clearance through dead-space washout facilitated by the high-flow of fresh air during expiration and the generation of positive pharyngeal pressure during expiration resulting from the continuous incoming flow, which can further aid in respiratory support [3]. Unlike traditional nasal prongs or masks, HFNO is not associated with discomfort caused by insufficient heat and humidity; thus, enhancing patient compliance.
HFNO is increasingly applied to address hypoxemia in spontaneously breathing critically ill patients [4]. Several investigations have demonstrated that HFNO surpasses traditional methods of oxygen administration at enhancing arterial oxygenation and patient comfort while decreasing respiratory rate, shortness of breath, and clinical manifestations of respiratory distress. Patients unresponsive to conventional oxygen therapy, such as those with hypoxemic acute respiratory failure, may especially benefit from HFNO. Additionally, HFNO may help prevent post-extubation respiratory failure and reintubation by ensuring adequate oxygenation, promoting airway clearance, and reducing the work of breathing. Furthermore, for patients with acute cardiogenic pulmonary edema, HFNO may improve oxygen delivery while reducing cardiac afterload through the generation of mildly positive intrathoracic pressure.
In anesthesia-related procedures, preoxygenation focuses on enhancing patient safety during intubation. For individuals with known or expected difficult airways, HFNO improves oxygenation, patient comfort, and procedural safety, as evidenced by a lower incidence of desaturation episodes. In critically ill patients, tracheal intubation is often complicated by adverse events, with oxygen desaturation among the most frequent, potentially leading to cardiac arrest despite pre-intubation oxygenation. HFNO can be used to sustain oxygenation during laryngoscopy, thereby ensuring effective high-flow apneic oxygenation.
The study by Kim et al. [5], published in this issue of the Korean Journal of Anesthesiology, contributes significantly to our understanding of apneic oxygenation by comparing HFNO with standard low-flow nasal oxygenation. This randomized controlled trial provides an enhanced perspective on the clinical utility of HFNO, specifically in mitigating hypoxemia-related interruptions during apneic procedures. This study reports that, while HFNO does not improve the lowest peripheral oxygen saturation levels compared to standard low-flow oxygenation, it significantly reduces the incidence of hypoxemia-related surgical interruptions and attenuates the decline in arterial oxygen tension during the apneic period. These findings highlight the potential of HFNO for improving procedural efficiency and patient safety.
This study also raises intriguing questions regarding the physiological mechanisms underlying HFNO. The generation of positive end-expiratory pressure, even with an open mouth, and its contribution to the maintenance of oxygenation during apnea are areas for future investigation. Additionally, its utility in patients with compromised oxygen reserves, such as those with obesity or pulmonary comorbidities, merits further investigation. As anesthesiologists continue to innovate in pursuit of better patient outcomes, HFNO has become a promising tool for perioperative oxygenation.
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Conflicts of Interest
No potential conflict of interest relevant to this article was reported.