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Cricoid pressure impedes positioning and ventilation through the laryngeal mask airway

Abstract

Purpose

To assess the effect of cricoid pressure on the positioning of and ventilation through the laryngeal mask airway (LMA).

Methods

In a double-blind, randomized design, the LMA was inserted with (CP[+] group, n = 20) or without double-handed cricoid pressure (CP[−] group, n = 20). Ventilation through the LMA was assessed by measuring expiratory tidal volume and judged as adequate when a mean expiratory tidal volume of ≥10 ml · kg−1 could be obtained. The LMA position was examined by fibreoscopy. The position of the mask relative to the cricoid cartilage and the cervical spine was radiologically examined (n = 10 in each group).

Results

Ventilation was adequate in all patients in the CP[−] group but in only five patients (25%) of the CP[+] group (P < 0.001). The glottis was visible fibreoptically below the mask aperture in all patients in the CP[−] group, but in only three patients in the CP[+] group (P < 0.001). Fibreoscopy showed that the mask was not inserted far enough in the remaining 17 patients of the CP[+] group. The reason for unsuccessful ventilation in the CP[+] group was excessive gas leakage (n = 2) and/or partial or complete airway obstruction (n = 13), which was noted fibreoptically. The radiographs showed that the tip of the mask in the CP[−] group was located below the level of the cricoid cartilage (C6 or C7 vertebra). The mask tip in the CP[+] group was above this level (C4 or C5 vertebra) (P < 0.01).

Conclusion

Cricoid pressure impedes positioning of and ventilation through the LMA.

Résumé

Objectif

Vérifier l’influence de la pression cricoïdienne sur la ventilation au masque laryngé (ML) et son positionnement.

Méthodes

Au cours de cette étude aléatoire et en double aveugle, le LM a été inséré avec (groupe CP[+], n = 20) ou sans pression cricoïdienne manuelle (groupe CP[−], n = 20). La ventilation par masque laryngée était évaluée par la mesure du volume courant expiré et jugée suffisante lorsqu’on obtenait un volume minute expiré ≥10 ml · kg−1. La position du ML était vérifiée par fibroscopie. Chez dix patients de chaque groupe, l’examen radiologique a déterminé la position du ML relativement au cartilage cricoïde et à la colonne cervicale.

Résultats

La ventilation a été adéquate chez tous les patients du groupe CP[−] mais chez seulement cinq (25%) du groupe CP[+] (P < 0,001). La glotte était visible par fibroscopie sous l’ouverture du masque chez tous les patients du groupe CP[−], mais chez seulement trois du groupe CP[+]. La fibroscopie a montré que le masque n ’était pas inséré assez profondément chez les 17 autres patients du groupe CP[+]. Cet échec ventilatoire dans le groupe CP[+] était causé par une fuite de gaz exagérée (n = 2) ou/et par l’obstruction des voies aériennes partielle ou complète (n = 13), vérifiée par fibroscopie. Les radiographies ont révélé que la pointe du masque dans le groupe CP[−] était située sous le niveau du cartilage cricoïde (C6 ou C7). Dans le groupe CP[+], la pointe du masque était située à un niveau plus élevé (C4 ou C5, P < 0,01).

Conclusion

La pression cricoïdienne nuit et à la ventilation au masque laryngé et a son positionnement.

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Correspondence to Kazuyoshi Aoyama.

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Aoyama, K., Takenaka, I., Sata, T. et al. Cricoid pressure impedes positioning and ventilation through the laryngeal mask airway. Can J Anaesth 43, 1035–1040 (1996). https://doi.org/10.1007/BF03011906

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Key words

  • Airway: laryngeal mask
  • Anaesthetic Technique: cricoid pressure
  • Equipment: airway, laryngeal mask