In a manikin study, Jepsen et al.1 showed that anaesthesia residents performed tracheal intubation significantly faster with the McGrath videolaryngoscope (VLS) than with the flexible fibreoptic endoscope (FFE) and achieved a higher success rate in two out of three simulated difficult airway scenarios. Their results suggest potential benefits of using a VLS in difficult airway management, but there are several aspects of this study that need to be discussed.
First, three difficult airway scenarios were simulated: pharyngeal obstruction, pharyngeal obstruction with cervical rigidity, and tongue oedema. The authors emphasised that the residents were instructed to perform intubation during simulated general anaesthesia. However, for patients with a known difficult airway caused by the scenarios which were simulated, difficult airway algorithms recommend awake intubation.2 Head and neck abnormalities have been associated with a high failure rate using videolaryngoscopy.3 Large upper airway or pharyngeal space-occupying lesions may preclude the use of a VLS because of a lack of space for insertion of the device. Moreover, the patient with limited mouth opening is not an appropriate candidate for videolaryngoscopic intubation.4 When dealing with these patients with altered upper airway anatomy, awake fibreoptic intubation is an absolutely vital skill. We are concerned that this study may misdirect clinicians to believe that tracheal intubation using a VLS under general anaesthesia represents a paradigm shift in known difficult airway management because it is easier to learn. This may discourage those anaesthesiologists unfamiliar with awake fibreoptic intubation from trying to master this important technique.
Second, in the introduction, the authors describe fibreoptic intubation as a complex, technically demanding skill to acquire. In the discussion, the authors mention that novice users require less than six attempts to achieve a success rate of more than 90% with the McGrath VLS, whereas an acceptable level of technical expertise may be acquired within 10 intubations with the FFE. Is videolaryngoscopic intubation really easier to master than fibreoptic intubation? In a survey of airway training, new residents found fibreoptic intubation easier to learn than videolaryngoscopic intubation, achieving a higher success rate with less trauma sooner with fibreoptic intubation than direct laryngoscopy and subsequent videolaryngoscopy.5
Third, the authors compared the Cormack and Lehane grades obtained by the FFE and McGrath VLS. However, Cormack and Lehane originally proposed their laryngoscopic view grades during laryngoscopy using a Macintosh blade, which requires alignment of the oral, pharyngeal and laryngeal axes.6 Also, the grade of the glottic view obtained using the Macintosh laryngoscope is often used as a primary variable for difficult or failed intubation. In contrast, use of the FFE or McGrath VLS to visualise the larynx does not require alignment of three airway axes, because these devices offer the ability to ‘look around the corner’. Moreover, what usually determines successful intubation with the FFE or McGrath VLS is not the grade of glottic view (which is often grade 1), but the alignment of the device and subsequent trajectory of the tracheal tube into the glottis. Actually, the glottic view grades obtained by the devices in this study were not related to the success rates of tracheal intubation with them. We would, therefore, argue that use of the Cormack and Lehane grades to compare performances of the FFE and McGrath VLS is irrational and insignificant.
Fourth, in this study, dental clicks were used as indication of dental damage, and the incidence of dental clicks was up to 30 to 32% during fibreoptic intubation. The authors attributed all these dental clicks to insertion of the Berman airway. However, dental damage by inserting the Berman airway is impossible in anaesthetised patients. This suggests that the manikin may not precisely reproduce the intubation conditions of real patients, and manikin studies can reveal results that are impossible to interpret in clinical practice. Thus, great caution must be taken when interpreting the findings from any manikin study.
Finally, their statement that no other study has compared performance of the fibreoptic and videolaryngoscopic intubations in difficult airway management is inexact. Rosenstock et al.7 compared the FFE and McGrath VLS for awake orotracheal intubation in adult patients with an anticipated difficult intubation, and found no difference between the two techniques in intubation time or success rate.
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1. Jepsen CH, Gätke MR, Thøgersen B, et al. Tracheal intubation with a flexible fibreoptic scope or the McGrath videolaryngoscope in simulated difficult airway scenarios. Eur J Anaesthesiol
2. American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology
3. Aziz MF, Healy D, Kheterpal S, et al. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2004 Glidescope intubations, complications, and failures from two institutions. Anesthesiology
4. Rothfield KP, Russo SG. Videolaryngoscopy: should it replace direct laryngoscopy? A pro-con debate. J Clin Anesth
5. Pott LM, Randel GI, Straker T, et al. A survey of airway training among U.S. and Canadian anesthesiology residency programs. J Clin Anesth
6. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia
7. Rosenstock CV, Thogersen B, Afshari A, et al. Awake fiberoptic or awake video laryngoscopic tracheal intubation in patients with anticipated difficult airway management: a randomized clinical trial. Anesthesiology