Abstract
Purpose
In order to minimize the potential for dental damage and to improve laryngeal visualization during tracheal intubation, two commonly used laryngoscope blades were modified and compared in a clinical setting: the Miller laryngoscope blade and the Macintosh laryngoscope blade. Modified versions of both laryngoscope blades with a lowered heel (Callander modification) at the proximal end of the blade were compared to standard blades.
Methods
Forty patients scheduled for general anesthesia requiring endotracheal intubation were studied prospectively. Preoperatively, the patients’ airways were evaluated according to Mallampati score, thyromental distance and interincisor gap. After induction of anesthesia laryngoscopy was performed with the original laryngoscope and its modified counterpart in random order. A lateral x-ray of the neck was taken after the optimal view had been obtained, and blade-tooth distance, laryngeal view, blade-tooth contact and need for assistance were measured. Using angular calculations the laryngoscopes were analyzed at different insertion depths on graph paper, and the results were compared with data from the lateral x-rays.
Results
With a modified Macintosh blade the blade-tooth distance was significantly greater in comparison to the original design (2.5 ± 2.1 cmvs 0.2 ± 0.1 cm,P < 0.01). Consequently the number of blade-tooth contacts was significantly lower (20%vs 75%,P < 0.05). The best laryngeal view could be obtained using a modified Macintosh laryngoscope. With a modified Miller laryngoscope laryngeal visibility was not improved and assistance was required more often to achieve adequate intubating conditions (35%vs 5%,P < 0.05).
Conclusion
A reduction of the proximal flange of a Miller blade decreases the blade’s effectiveness for laryngeal visualization, whereas a similar modification of a Macintosh blade increases blade-tooth distance, decreases the number of blade tooth contacts and provides a better laryngeal view.
Résumé
Objectif
Pour réduire le risque de dommage aux dents et pour améliorer la visualisation du larynx pendant ľintubation endotrachéale, deux lames de laryngoscope fréquemment utilisées ont été modifiées et comparées en situation clinique, celles des laryngoscopes Miller et Macintosh. Les versions modifiées des deux lames, munies ďun talon plus bas à ľextrémité proximale (modification Callander), ont été comparées aux lames régulières.
Méthode
Quarante patients devant subir une anesthésie générale avec intubation endotrachéale ont fait ľobjet ďune étude prospective. Ľévaluation préopératoire des voies respiratoires selon le score de Mallampati a révélé la distance thyromentonnière et ľespace interincisive. Après ľinduction de ľanesthésie, la laryngoscopie a été réalisée avec le laryngoscope original et sa version modifiée suivant un ordre aléatoire. Une fois la vision optimale obtenue, une radiographie latérale du cou a été prise, puis la distance entre la lame et les dents, la vision laryngée, la présence de contact entre la lame et les dents et la nécessité ďune assistance ont été évaluées. D’après le calcul des angles, une analyse graphique des laryngoscopes a été faite pour différentes profondeurs ďinsertion et les résultats comparés avec les données de la radiographie latérale.
Résultats
Avec la lame Macintosh modifiée, la distance dentlame a été significativement plus grande qu’avec la lame originale (2,5 ± 2,1 cm vs 0,2 ± 0,1 cm, P < 0,01). Le nombre de contacts dent-lame a donc été significativement plus bas (20 % vs 75 %, P < 0,05). La meilleure vision laryngée a pu être obtenue avec une lame Macintosh modifiée. Avec le laryngoscope Miller modifié, la visibilité du larynx n’était pas améliorée et une assistance a été plus souvent requise pour atteindre des conditions ďintubation adéquates (35 % vs 5 %, P < 0,05).
Conclusion
Une réduction du manche proximal de la lame Miller diminue la qualité de la visualisation laryngée obtenue tandis qu’une modification similaire de la lame Macintosh améliore la distance dent-lame, diminue le nombre de contacts dent-lame et fournit une meilleure vision du larynx.
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Kimberger, O., Fischer, L., Plank, C. et al. Lower flange modification improves performance of the Macintosh, but not the Miller laryngoscope blade. Can J Anesth 53, 595–601 (2006). https://doi.org/10.1007/BF03021851
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DOI: https://doi.org/10.1007/BF03021851