To the Editor:

In a multicentered, observational study comparing the success rate of commonly used rescue intubation techniques after a failed direct laryngoscopy, Aziz et al.1  showed that video laryngoscopy was associated with a higher success rate of rescue intubation and was more commonly used than other tools, including a fiberoptic bronchoscope, a supraglottic airway device, an optical stylet, and a lighted stylet. In addition to the limitations described in the discussion, however, there are several questions in this study that must be clarified.

First, the majority of rescue intubations (1,023 of 1,511 cases, 68%) were defined after one failed direct laryngoscopy attempt. This practice is not in agreement with the definition of difficult or failed laryngoscopy in the current practice guidelines for difficult airway management by the American Society of Anesthesiologists.2  Because the authors did not provide the detailed causes of failed direct laryngoscopy, it was unclear why the anesthetists abandoned direct laryngoscopy after the first attempt. In fact, difficulty in performing laryngoscopy depends on the anesthetists’ level of skill, the patient’s features, and procedure circumstances. In this study, the authors did not specify whether an optimal-best laryngoscopy attempt was executed when a failed direct laryngoscopy was defined. The components of an optimal-best laryngoscopy attempt include a reasonably experienced (at least 3 full recent years) anesthetist, use of an optimal sniffing position, change of length or type of blade one time, and use of external laryngeal manipulation.3  Only when an optimal-best laryngoscopy attempt is performed may difficult or failed laryngoscopy be readily obvious to an experienced anesthetist on the first attempt and thus is independent of both number of laryngoscopy attempts and time. According to the data provided by the authors, we cannot determine whether a definitively failed direct laryngoscopy occurs in each patient receiving rescue intubation.

Second, in this study, the failed direct laryngoscopy included the use of a device without a tube passage attempt, although the goal of direct laryngoscopy is to carry out tracheal intubation. It must be emphasized that the laryngeal view obtained by direct laryngoscopy is often used as an important variable for difficult or failed intubation, but they are not synonymous in most patients.3  Successful intubation is dependent more on the skill level of the anesthetists than on the laryngeal view obtained by direct laryngoscopy, and thus the degrees of difficulty with direct laryngoscopy and tracheal intubation may be incompatible. For example, some patients with a class 3 or 4 laryngeal view may be successfully intubated by an experienced anesthetist on the first or second attempt if the distal end of the tracheal tube is suitably curved by a malleable stylet or an intubating introducer (e.g., a gum-elastic bougie).4  Actually, 61 of 1,619 patients with failed direct laryngoscopy in this study had a return to direct laryngoscopy again for airway rescue. Thus, when defining a failed direct laryngoscopy, the exclusion of a tube passage attempt is unreasonable.

Third, the success rate of rescue intubation with the supraglottic airway device was described as the final endpoint of performance. The final goal of airway management is maintenance of oxygenation rather than performing tracheal intubation. After a failed initial intubation attempt, restitution of ventilation by either a noninvasive (i.e., supraglottic airway device) or an invasive intervention is the priority.5  Thus, use of the supraglottic airway device as a rescue tool of failed direct laryngoscopy can not only provide a conduit to intubate the trachea but also is an effective ventilatory measure with a high success rate.6  If the rescue intubation via the supraglottic airway device is unsuccessful, the existence of an effective airway can evidently be lifesaving. Thus, we argue that only comparing the success rate of rescue intubation using video laryngoscopy and a supraglottic airway device after failed direct laryngoscopy in this study is not a complete comparison.

Finally, video laryngoscopy provided a high success rate of rescue intubation after failed direct laryngoscopy but did not give a 100% success rate. This suggests that when attempting to rescue a failed direct laryngoscopy, no single device can address all issues. Furthermore, we agree with Hagberg et al.5  that no one tool is better than others in all conditions, because each tool has individual properties that may be advantageous in some conditions but disadvantageous in others. The use of video laryngoscopy as the first rescue choice at the early stage of failed direct laryngoscopy seems rational,7  but an important problem we are facing is what anesthetists should do if difficult video laryngoscopy occurs. In fact, recent work shows that first attempt failure at intubation using video laryngoscopy is also associated with increased complications.8  Thus, we believe that to rescue a failed direct laryngoscopy expeditiously and safely, anesthetists must master the several different airway devices and should use the techniques with which they have the most experience and competence, with strict adherence to the current practice guidelines for difficult airway management.

Competing Interests

The authors declare no competing interests.

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