title: Indirect videolaryngoscopy using Macintosh blades in patients with non-anticipated difficult airways results in significantly lower forces exerted on teeth relative to classic direct laryngoscopy: a randomized crossover trial.
abstract: BACKGROUND
  Videolaryngoscopy has proven advantageous over direct laryngoscopy for a variety of outcome variables, most importantly, making laryngoscopy more successful. We tested whether three videolaryngoscopes (VLS), McGrath® series 5 (Aircraft Medical Ltd, Edinburgh, UK), C-MAC® (Karl Storz, Tuttlingen, Germany) and GlideScope® Cobalt (Verathon Medical, Bothell, WA, USA) exert reduced forces on maxillary incisors and lower teeth, and compared them with a classic Macintosh MAC 3 laryngoscope blade during laryngoscopy.
  
  
  METHODS
  In this randomized crossover trial, we included 141 patients (ASA I-III) with non-anticipated difficult airways. They were randomly allocated to undergo direct laryngoscopy and videolaryngoscopy performed with one of three VLS. Primary outcome was the magnitude of forces applied to the maxillary incisors during laryngoscopy. Secondary outcomes were the frequency with which forces were applied, and the magnitude of forces applied to the lower teeth.
  
  
  RESULTS
  Forces applied to the maxillary incisors during direct classic laryngoscopy were on average higher than forces applied during videolaryngoscopy. Among the VLS the average force applied was significantly lower for the C-MAC® as compared to the McGrath® and the GlideScope® VLS. The frequency with which a force was applied to the maxillary incisors was significantly lower for the C-MAC®, compared to the other VLS and classic Macintosh laryngoscope. The number of cases in which force was applied to the lower teeth was smallest for the McGrath VLS.
  
  
  CONCLUSIONS
  Forces exerted on maxillary incisors are lower using video-assisted Macintosh blade laryngoscopy compared to classic direct laryngoscopy. The number and magnitude of forces applied to maxillary incisors also differ substantially between different VLS.
authors.affiliation: Department of Anesthesiology, Intensive Care and Pain Therapy, Catharina Hospital Eindhoven, Eindhoven, The Netherlands - vanzundertandre@gmail.com.
authors.forename: B
authors.initials: B
authors.lastname: Pieters
authors.forename: R
authors.initials: R
authors.lastname: Maassen
authors.forename: E
authors.initials: E
authors.lastname: Van Eig
authors.forename: B
authors.initials: B
authors.lastname: Maathuis
authors.forename: J
authors.initials: J
authors.lastname: Van Den Dobbelsteen
authors.forename: A
authors.initials: A
authors.lastname: Van Zundert
mesh_terms: D000328:Adult; D000368:Aged; D058109:Airway Management / Q000009:adverse effects / Q000379:methods*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000009:adverse effects / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018677:Tooth Injuries / Q000453:epidemiology / Q000209:etiology*