Airway risk factors for the Miller laryngoscope blade

The role of airway risk factors impeding orotracheal intubation during Miller blade laryngoscopy has not been formally examined in a large-scale study in adults. A high degree of success for orotracheal intubation during Miller blade laryngoscopy was observed with a novel finding of different sets of airway risk factors impeding the process of laryngoscopy and orotracheal intubation.

Study objectiveThe purpose of this study was to analyze previously reported airway risk factors in the performance of Miller laryngoscopy and orotracheal intubation.DesignProspective, observational study.SettingOperating rooms.PatientsA total of 978 American Society of Anesthesiologists I-III adults requiring general orotracheal anesthesia for elective surgery.InterventionsNone.MeasurementsNine previously reported airway risk factors used in predicting difficult laryngoscopy, modified McCormack-Lehane views observed during initial unaided Miller blade laryngoscopy, and number of attempts or need for alternate airway tools to facilitate orotracheal intubation.Main resultsOrotracheal intubation occurred in 941 of 978 (96.2%) patients with the Miller blade, although 8 patients required 3 attempts, with the remaining 37 patients requiring alternate airway tools. There were no failed orotracheal intubations. Multivariable analysis revealed that modified Mallampati class, thyromental distance, and ability to prognath were associated with progressively inferior modified Cormack-Lehane views, whereas modified Mallampati class, height, and head and neck extension were associated with progressive difficulty with orotracheal intubation.ConclusionsThe Miller blade is highly successful in the performance of direct laryngoscopy for orotracheal intubation. These findings suggest that different sets of airway risk factors affect the process of laryngoscopy and orotracheal intubation.