Preoxygenation in Critically Ill Patients Requiring Intubation: Difficult Questions, No Easy Answers.

Airway management in critically ill patients remains a fundamental but challenging procedure, characterized by a high rate of complications. Studies have shown that as many as 40% of intubations in critical care settings are accompanied by severe adverse events,1,2 the most frequent complication being hypoxemia. A prospective study from critical care units in Scotland reported that severe hypoxemia (SpO2 80%) during endotracheal intubation occurred in 22% of subjects, despite the procedure being carried out by highly skilled teams.3 Patient factors, expertise of the intubating clinician, choice and dose of induction and neuromuscular blocking drugs, and pre-induction management all contribute to safety and outcome.3 In the operating room, one crucial step to minimize desaturation during intubation is preoxygenation by administering high oxygen concentration via face mask. Unfortunately, preoxygenation of critically ill patients is less effective.4,5 Different techniques for preoxygenation have been investigated in the intensive care setting. Tightly fitting bag-valve-mask proved to be only marginally effective.4,6 Noninvasive ventilation delivered via face mask for a 3-min period pre-intubation appears to aid in reducing arterial oxyhemoglobin desaturation during the procedure,7 although no large randomized trials have confirmed these findings. A limitation of this technique is that its use must be interrupted during laryngoscopy, reducing the benefits, and this may account for its frequent failure to prevent desaturation. In recent years, high-flow nasal cannula (HFNC) has gained attention in critical care due to its capacity to generate positive airway pressure, using a small interface and heated and humidified air flow, providing greater comfort than traditional oxygen therapy.8 These features make it an attractive candidate for improving preoxygenation as well as maintaining apneic oxygenation during intubation attempts in the critically ill. MiguelMontanes et al9 compared non-rebreathing bag reservoir face mask with HFNC for preoxygenation before endotracheal intubation of intensive care subjects with mild to