Canadian Journal of Anaesthesia

, Volume 41, Issue 7, pp 589–593

Laryngeal mask airway cuff pressure and position during anaesthesia lasting one to two hours

  • J. Brimacombe
  • A. Berry
Reports of Investigation

Abstract

The cuff of the laryngeal mask airway (LMA) is highly permeable to nitrous oxide (N2O), and cuff pressure increases during N2O/O2 anaesthesia. The extent of these changes and their effect on LMA position have previously only been investigated for short procedures. The current study was designed to investigate the effects of nitrous oxide-oxygen (N2O/O2) anaesthesia lasting one to two hours on cuff pressure, LMA positioning and pharyngeal morbidity. Twenty-four male patients underwent spontaneous ventilation anaesthesia with 66% N2O in oxygen and isoflurane. Following insertion and inflation of a #4 LMA with 30 ml air, mean (SD) cuff pressures immediately increased from 107 (9) to 145 (12) mmHg and then at a decreasing rate for 90 min to peak at 215 (12) mmHg. There was a correlation between N2O concentration and final cuff volume (P < 0.001). There was no displacement of the LMA cuff in any patient. Three of 19 patients had a mild sore throat. This study demonstrates that the increase in LMA cuff pressure is self limiting over a one-to-two-hour period and does not cause displacement of the LMA. There is no evidence that cuff pressure monitoring and pressure limitation is necessary during LMA anaesthesia.

Key words

anaesthetics, gases: nitrous oxide equipment: laryngeal mask airway 

Résumé

Le coussinet du masque laryngé (ML) est hautement perméable au protoxyde d’azote (N2O), et sa pression augmente pendant l’anesthésie au N2O/O2. L’importance de ces changements et leur effet sur la position du ML n’ont été investigués précédemment que pour de courtes interventions. Cette étude propose d’investiguer les effets du mélange de protoxyde d’azote et d’oxygène (N2O/O2) sur la pression du coussinet au cours d’une anesthésie d’une à deux heures, ainsi que sur la position du ML et ses répercussions sur le pharynx. Vingt-quatre patients masculins sont soumis à une anesthésie en ventilation spontanée avec 66% de N2O dans l’oxygène et de l’isoflurane. Après l’insertion et l’inflation d’un ML #4 avec 30 ml d’air, les pressions moyennes (DS) du coussinet augmentent immédiatement de 107 (9) à 145 (12) mm de Hg et ensuite atteignent un pic de 215 (12) mm de Hg après une augmentation décroissante de 90 min. Il y a une corrélation entre la concentration de N2O et le volume final du coussinet (P < 0,001). Il n’y a eu de déplacement du coussinet du ML chez aucun patient. Trois des 19 patients ont eu une douleur modérée de la gorge. Cette étude démontre que l’augmentation de la pression du coussinet du ML se limite d’elle même après une période d’une à deux heures et ne provoque pas de déplacement du ML. Il n’y a pas d’argument indiquant que le monitorage de la pression du coussinet et sa limitation soient nécessaires au cours d’une anesthésie au ML.

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Copyright information

© Canadian Anesthesiologists 1994

Authors and Affiliations

  • J. Brimacombe
    • 1
  • A. Berry
    • 1
    • 2
  1. 1.Department of Anaesthesia and Intensive CareCairns Base HospitalCairnsAustralia
  2. 2.Department of AnaesthesiaRoyal Berkshire HospitalReadingUK

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