title: Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope.
abstract: BACKGROUND
  The GlideScope videolaryngoscope allows equal or superior glottic visualization compared with direct laryngoscopy, but predictive features for difficult GlideScope intubation have not been identified. We undertook this prospective study to identify patient characteristics associated with difficult GlideScope intubation.
  
  
  METHODS
  Demographic and morphometric factors were recorded preoperatively for 400 patients undergoing anesthesia with endotracheal intubation. After induction, direct laryngoscopy was performed in all patients to assess the Cormack and Lehane grade of glottic visualization followed by GlideScope intubation. The number of attempts and time needed for intubation were recorded. Univariate and multivariate analyses were performed to identify the characteristics associated with difficult GlideScope intubation.
  
  
  RESULTS
  Intubation required 1, 2, and 3 attempts in 342, 48, and 9 participants, respectively, with one failure. Mean time for intubation was 21 +/- 14 s. After univariate analysis, the following characteristics were significantly correlated (P < 0.05) with longer time to intubate and/or multiple attempts: older age, male sex, history of snoring, high Mallampati class, small mouth opening, short sternothyroid and manubriomental distances, large neck circumference, high upper lip bite test score, and high Cormack and Lehane grade during direct laryngoscopy. However, after introducing these variables in nominal logistic and proportional hazard multiple regression models, only high Cormack and Lehane grade during direct laryngoscopy, high upper lip bite test score, and short sternothyroid distance were significantly associated with multiple attempts or lengthier intubations.
  
  
  CONCLUSIONS
  Despite a high success rate, intubation with the GlideScope is likely to be more challenging in patients with high Cormack and Lehane grade during direct laryngoscopy, high upper lip bite test score, or short sternothyroid distance.
authors.affiliation: Department of Anesthesiology, CHUM, Hôpital Notre-Dame, 1560 Sherbrooke East, Montréal, Canada, H2L 4M1.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Tremblay
authors.forename: Stephan
authors.initials: S
authors.lastname: Williams
authors.forename: Arnaud
authors.initials: A
authors.lastname: Robitaille
authors.forename: Pierre
authors.initials: P
authors.lastname: Drolet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017558:Elective Surgical Procedures; D004867:Equipment Design; D005260:Female; D005931:Glottis / Q000033:anatomy & histology*; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects / Q000295:instrumentation*; D007574:Jaw Relation Record; D020704:Laryngoscopes; D007828:Laryngoscopy; D008046:Lip; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000033:anatomy & histology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012372:ROC Curve; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014741:Video Recording