Preventing leaks around a laryngeal mask airway


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I read with interest the letters by Dr Lenoir [1] and Drs Burnell and da Silva [2]. The author reports several occurrences of problems with adequacy of seal around single-use laryngeal masks and Burnell and da Silva, in their reply, suggest this may be a common problem in children [3]. Dr Lenoir's solution is to improve the seal between the airway and laryngeal mask with pressure on the anterior neck applied through a gel pad. Further inferred solutions include intentional over-inflation of the laryngeal mask cuff, managing ventilation with low pressures, using un-physiological inspiratory: expiratory ratios and using neuromuscular blockade where this was not previously planned. None of these appear intrinsically desirable, if they can be easily avoided.

These letters raise several issues. First, why has this problem not been reported before with re-usable laryngeal mask airways? Is this a feature more likely to be encountered with single-use devices (in these letters it appears the single-use devices were from Intavent Orthofix and Ambu), and if so, is this not a cause for concern [4]?

Second, the solution, while apparently simple and pragmatic, raises some minor concerns. What Lenoir describes is a solution to a poorly fitting laryngeal mask. Gas leaking out of the mouth is not a safety issue, unless it causes hypoventilation. It is entirely plausible, however, that with the solution advocated, the natural position of the mask may be altered and gas will continue to leak, but more will leak into the oesophagus. This phenomenon is well-known when a Classic™ laryngeal mask airway is used with high ventilating pressures [5] and is self-evidently potentially dangerous. Lenoir's solution to the problem also uses the gel pads in a fashion for which they were not designed; would this have medico-legal implications if problems were to ensure [6]? It is notable that the patient described by Lenoir was an asthmatic weighing 100 kg. While many anaesthetists are, some would not be comfortable ventilating the lungs of such a large patient with asthma through a laryngeal mask airway, under any circumstances.

There are several alternative solutions which might be considered if one does not wish to resort to tracheal intubation. First, forget the laryngeal mask airway, as it seems to be offering little benefit, and resort to a facemask and Claussen harness. Second, try a reusable laryngeal mask airway. The third and most simple solution, however, is to use a ProSeal® laryngeal mask airway (PLMA, Intavent Orthofix, Maidenhead, UK), which is designed for controlled ventilation. In a cross-over study performed 4 years ago, it was demonstrated that when using a PLMA with a ventilating pressure of 20 or 30 cmH2O the proportion of patients without an airway leak was 87% and 48%, while with a Classic laryngeal mask airway the figures were 41% and 4%, respectively [7]. The average airway seal with a PLMA exceeds that of the Classic LMA by at least 60–80%; its drain tube vents any gas leaking to the oesophagus and airway protection is increased. The PLMA performs equally well with or without neuromuscular blockade [8]. Overall, it can be argued that safety is likely to be improved by use of the PLMA [8].

Dr Lenoir's solution is inventive and realistically is unlikely to be harmful, but I would argue it is unnecessary. The PLMA offers a simple solution to this problem. However in those hospitals where wholesale transfer to single-use masks has occurred, this option is unfortunately not likely to be available.

Conflict of interest

Dr Cook has been paid by Intavent Orthofix and the LMA Company for lecturing. Both companies manufacture laryngeal mask airways including the ProSeal.