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Optimizing insertion of the ProSeal laryngeal mask airway

Royal United Hospital, Bath, UK, E-mail timcook{at}ukgateway.net

To the Editor:

O’Connor et al. report an incidence of ProSeal laryngeal mask airway (PLMA) glottic insertion of 6%.¹

We should not conclude the PLMA increases the risk of glottic insertion. In the first classic LMA (cLMA) fibreoptic study 4% of cLMA tips entered the glottis.² Unlike the cLMA, the PLMA drain tube enables rapid diagnosis of misplacement.

During 656 elective adult PLMA insertions (age 52 ± 17 yr, weight 76 kg, range 34–140 kg, > 90% unparalyzed) my first time success is 83.2%, overall success 99.8% and median seal pressure 33 cm H₂O. Most re-insertions were in patients who moved during insertion.

Glottic insertion is likely to cause complete airway obstruction. I have needed 12 reinsertions (1.8%) due to high airway pressure (5), stridor (5) or airway obstruction (2). These might be due to glottic insertion or: PLMA cuff infolding, arytenoid shortening, mask fold-over or laryngospasm. Differential diagnosis may be difficult, though an algorithm assists.³ My estimates for glottic insertion therefore range from 1.8% (all cases of partial obstruction or stridor) to 0.3% (all complete obstructions): compared to the 6% reported by O’Connor.

In explaining these differences it is noteworthy that O’Connor uses digital insertion. I routinely use the manufacturer’s introducer and anesthesia assistants provide mouth-opening, then jaw-thrust during insertion. The digital technique is used when this fails.

Finally O’Connor’s tests of glottic insertion have not been validated.⁴ When the test was ‘positive’ O’Connor replaced the PLMA, without fibreoptic examination to confirm accuracy of the test. An opportunity for validation has therefore been missed.

References

1 O’Connor CJ Jr, Stix MS, Valade DR. Glottic insertion of the ProSeal^TM LMA occurs in 6% of cases: a review of 627 patients. Can J Anesth 2005; 52: 199–204.[Abstract/Free Full Text]

2 Nandi PR, Nunn JF, Charlesworth CH, Taylor SJ. Radiological study of the laryngeal mask. Eur J Anaesthesiol Suppl 1991; 4: 33–9.[Medline]

3 Brimacombe J, Keller C. A proposed algorithm for the management of airway obstruction with the Proseal^TM laryngeal mask airway. Anesth Analg 2005; 100: 298–9.[Free Full Text]

4 O’Connor C Jr, Stix MS. Bubble solution diagnoses ProSeal^TM insertion into the glottis (Letter). Anesth Analg 2002; 94: 1671–2.[Free Full Text]

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REPLY

Cornelius J. O’Connor, Jr, Michael S. Stix, and Dennis R. Valade
CJA 2005 52: 886. [Full Text]  

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