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Predicting difficult intubation: a multivariable analysis

  • Keyvan Karkouti
  • D. Keith Rose
  • D. Wigglesworth
  • Marsha M. Cohen
Reports Of Investigation

Abstract

Purpose: To develop a clinically useful and valid model for predicting difficult laryngoscopic tracheal intubation in patients with seemingly normal airways by adhering to the principles of multivariable model development.

Methods: This was an observational study performed at a tertiary-care teaching hospital. Preoperatively, 444 randomly selected patients requiring tracheal intubation for elective surgery were assessed. In addition, 27 patients in whom tracheal intubation was difficult, but were not assessed properatively, were assessed postoperatively. One assessor, blinded to the intubation information, collected the predictor variables. A reliable definition for difficult intubation was used and all attempts were made to eliminate sources of bias. Multivariable modeling was performed using logistic regression and the model was validated using the bootstrapping technique.

Results: Of the 461 patients included in the analysis, 38 were classified as difficult to intubate. Multivariable analysis identified three airway tests that were highly significant for predicting difficult tracheal intubation. These were: 1) “mouth opening”, 2) “chin protrusion”, and 3) “atlanto-occipital extension”. Using these tests, a validated, highly reliable and predictive model is produced to determine the propability of difficult intubation for patients. At a selected probability cut-off value, the model is 86.8% sensitive and 96.0% specific.

Conclusion: A simple and accurate multivariable model, consisting of three airway tests, is produced for predicting difficult laryngoscopic tracheal intubation. Additional studies will be required to determine the accuracy and feasibility of this model when applied to a large sample of new patients by multiple anesthesiologists.

Keywords

Obstructive Sleep Apnea Tracheal Intubation Direct Laryngoscopy Difficult Intubation Difficult Tracheal Intubation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Résumé

Objectif: Élaborer un modèle valide et utilisable en clinique pour prédire des difficultés d’intubation trachéale laryngoscopique chez des patients qui ont apparemment des voies aériennes mormales. Utiliser, pour ce faire, les principes d’élaboration d’un modèle multivariable.

Méthode: Il s’est agi d’une observation réalisée dans un hôpital d’enseignement de soins tertiaires. Avant l’opération, on a évalué 444 patients choisis au hasard qui avaient besoin d’intubation endotrachéale pendant une intervention planifiée. De plus, 27 patients chez qui l’intubation a été difficile n’ont été évalués qu’après l’intervention. Un assistant, qui ne connaissait pas les conditions ’intubation, a enregistré les variables de prédiction. Une définition exacte de l’intubation difficile a été utilisée et on a tenté d’éliminer tout biais possible. Une modélisation à multivariables a été réalisée en utilisant une régression logistique et le modèle a été validé par la technique de l’amore («bootstrapping»).

Résultats: Des 461 patients inclus dans l’analyse, 38 ont été difficiles à intuber. L’analyse à multivariables a reconnu trois épreuves d’intubation comme hautement significatives pour prédire une intubation endotrachéale difficile: 1) «L’ouverture de la bouche», 2) «la protrusion du menton» et 3) «l’extension atlanto-occipitale». Avec ces tests, un modèle validé, très fiable et prédictif a été produit pour déterminer la probabilité d’intubation difficile. Pour une valeur limite de probabilité choisie, le modèle affichait une sensibilité de 86,8 % et une spécificité de 96,0 %.

Conclusion: Un modèle à multivariables simple et précis, fait de trois test d’intubation, a été produit pour prédire des difficultés d’intubation endotrachéale laryngoscopique. D’autres études demeurent nécessaires pour évaluer la fidélité de ce modèle quand il est appliqué à un échantillon important de nouveaux patients par différents anesthésiologistes.

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Copyright information

© Canadian Anesthesiologists 2000

Authors and Affiliations

  • Keyvan Karkouti
    • 1
  • D. Keith Rose
    • 2
  • D. Wigglesworth
    • 2
  • Marsha M. Cohen
    • 3
  1. 1.From the Departments of Anaesthesia, Toronto General HospitalUniversity Health NetworkCanada
  2. 2.St. Michael’s HospitalUniversity of TorontoCanada
  3. 3.the Center for Research in Women’s Health, Department of Health Administration, and Department of Anaesthesia, Sunnybrook Health Science CenterUniversity of TorontoCanada

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