title: A deliberately restricted laryngeal view with the GlideScope® video laryngoscope is associated with faster and easier tracheal intubation when compared with a full glottic view: a randomized clinical trial.
abstract: BACKGROUND
  During video laryngoscopy (VL) with angulated or hyper-curved blades, it is sometimes difficult to complete tracheal intubation despite a full view of the larynx. When using indirect VL, it has been suggested that it may be preferable to obtain a deliberately restricted view of the larynx to facilitate passage of the endotracheal tube. We used the GlideScope® GVL video laryngoscope (GVL) to test whether deliberately obtaining a restricted view would result in faster and easier tracheal intubation than with a full view of the larynx.
  
  
  METHODS
  We recruited 163 elective surgical patients and randomly allocated the participants to one of two groups: Group F, where a full view of the larynx was obtained and held during GVL-facilitated tracheal intubation, and Group R, with a restricted view of the larynx (< 50% of glottic opening visible). Study investigators experienced in indirect VL performed the intubations. The intubations were recorded and the video recordings were subsequently assessed for total time to intubation, ease of intubation using a visual analogue scale (VAS; where 0 = easy and 100 = difficult), first-attempt success rate, and oxygen saturation after intubation. Complications were also assessed.
  
  
  RESULTS
  The median [interquartile range (IQR)] time to intubation was faster in Group R than in Group F (27 [22-36] sec vs 36 [27-48] sec, respectively; median difference, 9 sec; 95% confidence interval [CI], 5 to 13; P < 0.001). The median [IQR] VAS rating for ease of intubation was also better in Group R than in Group F (14 [6-42) mm vs 50 mm [17-65], respectively; median difference, 20 mm; 95% CI, 10 to 31; P < 0.001). There was no difference between groups regarding the first-attempt success rate, oxygen saturation immediately after intubation, or complications.
  
  
  CONCLUSIONS
  Using the GVL with a deliberately restricted view of the larynx resulted in faster and easier tracheal intubation than with a full view and with no additional complications. Our study suggests that obtaining a full or Cormack-Lehane grade 1 view may not be desirable when using the GVL. This trial was registered at ClinicalTrials.gov: NCT02144207.
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Robert
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Kovacs
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Milne
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Morris
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Orlando
authors.initials: O
authors.lastname: Hung
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada.
authors.forename: Kirk
authors.initials: K
authors.lastname: MacQuarrie
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford St., PO Box 15000, Halifax, NS, B3H 4R2, Canada.
authors.forename: Sean
authors.initials: S
authors.lastname: Mackinnon
authors.affiliation: Department of Anesthesia, Pain Management and Perioperative Medicine, QEII Health Sciences Centre, Dalhousie University, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS, B3H 3A7, Canada. jlaw@dal.ca.
authors.forename: J
authors.initials: J
authors.lastname: Adam Law
mesh_terms: D000328:Adult; D000368:Aged; D004867:Equipment Design; D005260:Female; D005931:Glottis; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation* / Q000379:methods*; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000295:instrumentation* / Q000379:methods; D007830:Larynx; D008297:Male; D008875:Middle Aged; D013995:Time; D014741:Video Recording