Response to: ‘Failed supraglottic airway’: an algorithm for suboptimally placed supraglottic airway devices based on videolaryngoscopy

Editor—We read with interest the editorial by van Zundert and colleagues¹ in the recent issue of British Journal of Anaesthesia. We strongly commend the authors for highlighting the problem of suboptimal laryngeal mask airway (LMA) placement. As a single specialty ear, nose, and throat hospital, we are perhaps in a unique position in that the majority of our caseload is shared airway using first-generation flexible LMAs. Since the flexible LMA was introduced at our hospital in 1990, we estimate that we have performed >135 000 ENT operations, with 80–85% performed with flexible LMAs. This includes a large number of shared airway procedures, such as tonsillectomy. These procedures, in themselves, are a good test of LMA function, requiring the maintenance of optimal ventilation whilst also protecting the larynx from blood and debris.

We would, however, like to discuss a number of points raised in the article, including the anatomical relationship between the LMA and patient, rescue manoeuvres, and the use of videolaryngoscopy after LMA insertion. In both the original article² and the subsequent editorial,¹ the authors made a number of assertions regarding the relationship between anatomy and LMA function, which they have used as the basis of a grading system. Although we agree that the epiglottis can cause partial or complete obstruction of the LMA, it does not have to be seated on the anterior aspect of the rim of the proximal LMA cuff to function correctly. Indeed, in patients with a short laryngeal inlet it may be preferable to have part of the epiglottis within the bowl of the LMA. Downsizing to a smaller LMA to align its posterior rim with the epiglottis, as suggested by the authors’ algorithm, could lead to deterioration in the overall LMA seal. In such instances, a distally sited LMA may open posterior to the arytenoids, causing obstruction to gas flow.

We agree that a jaw thrust greatly increases the chances of achieving a well-positioned LMA. When used in combination with Brain’s original description of LMA insertion,³ using the index finger to guide the LMA cuff into the hypopharynx, first-time insertion success rates are maximized. If initial attempts fail, the narrow shaft of the flexible LMA facilitates the use of Magill forceps to guide the LMA beyond the epiglottis under direct laryngoscopy.

The authors have suggested videolaryngoscopy to confirm correct LMA placement. However, we question this part of the algorithm, because minimal laryngoscopic force alters the relationship between the epiglottis, base of tongue, and LMA, potentially displacing it from its original position. Thus, attempting to define a grading system on this basis may lead to misdiagnosis of the cause of suboptimal function.

Other issues not addressed in the algorithm are the presence of laryngospasm because of a light plane of anaesthesia, or vocal cord squeeze from an overinflated LMA cuff. In both instances, the position of the LMA may be anatomically correct, but oropharyngeal leak pressures will be greatly reduced. Corrective measures, such as laryngoscopy with or without Magill forceps, may therefore be counter-productive.

In summary, we believe that this editorial¹ has highlighted the current shortfalls in LMA practice. However, we do not believe a grading system based on videolaryngoscopy is the correct approach to an issue not easily categorized. Instead, appropriate training and practice, focusing on correct insertion technique, may be more beneficial.

Declaration of interest

A.B. invented the Laryngeal Mask Airway. No other conflicts of interest declared.

References