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Canadian Journal of Anesthesia 50:967-968 (2003)
© Canadian Anesthesiologists' Society, 2003

Correspondence

REPLY

M. Zubair Ahmed, MB BS FRCA and Akbar Vohra, MB CHB DA FRCA

London, UK

We thank Dolling et al. for their comments and appreciate this opportunity to reply. We note fundamental differences in the methodology of the study by Dolling and ours:1

- rigid vs reinforced laryngeal mask airway (LMA);
- oral vs nasal surgery;
- spontaneous vs controlled ventilation;
- pediatric vs adult patients;
- no suctioning vs suctioning at the end of the procedure.

All of which may have contributed to the differing results.

The LMA protects the airway by covering it and movement of the LMA will reduce this protection. Oral surgery and a rigid LMA are likely to result in increased LMA movement. Increased LMA movement, combined with the negative pressure created by spontaneous breathing, will encourage blood to breach the LMA barrier and contaminate it from the inside.

The shape of the LMA is based on adult anatomy and pediatric masks are the downsized version of adult masks. It can be postulated that pediatric masks do not make an effective seal because of the differences between adult and pediatric upper airway anatomy. We are not aware of any work on this. Finally, if secretions or blood are not cleared at the end of the procedure, this is likely to result in increased LMA contamination upon withdrawal.

We have also observed that overinflating the LMA cuff distorts its shape and reduces the area of contact with the pharynx, thus worsening the seal. We do not know how the authors assessed the adequacy of the seal in their study. This may be an additional factor explaining higher contamination scores.

We agree that further studies using reinforced LMA and direct scoring with endoscopic examinations may clarify the situation.

Reference

1 Ahmed MZ, Vohra A. The reinforced laryngeal mask airway (RLMA) protects the airway in patients undergoing nasal surgery – an observational study of 200 patients. Can J Anesth 2002; 49: 863–6.[Abstract/Free Full Text]


Related articles in CJA:

Protection of the airway with the LMA during upper airway surgery
Stuart Dolling, Nicola R.K. Anders, and Sian E. Rolfe
CJA 2003 50: 967. [Full Text]  




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