title: Validation of a model of graded difficulty in Laerdal SimMan: functional comparisons between Macintosh, Truview EVO2, Glidescope Video Laryngoscope and Airtraq.
abstract: OBJECTIVE
  A randomised, cross-over study was designed to validate a new model of graded difficulty (based on mandibular space reduction) in the Laerdal 'SimMan' mannnequin and to suggest functional comparisons between Macintosh. Glidescope Video Laryngoscope, Truview EVO2 and Airtraq.
  
  
  METHODS
  Twenty anaesthetists attempted intubation with all four laryngoscopes in three settings: easy, intermediate (based on a custom-made removable prosthetic insert) and difficult ('tongue oedema', a mannnequin feature). Laryngoscopic view and time to intubate were the primary outcome measures. Other measures were successful intubation, ease of laryngoscopy [visual analogue scale (VAS)] and intubation (VAS), tongue compression score and number of attempts.
  
  
  RESULTS
  Between settings comparisons demonstrated that Macintosh, Glidescope and Airtraq had worsening scores from easy to intermediate with lesser changes for Truview. However, with the intermediate to difficult comparison, Airtraq was the only blade with no worsening of scores. Within-blade comparisons showed that Macintosh was superior over all in both the easy and intermediate settings, whereas Airtraq was the most successful blade in the difficult setting.
  
  
  CONCLUSIONS
  Our study suggests that Glidescope and, to some extent Truview, are functionally similar to Macintosh and suffer from similar limitations in the difficult setting. On the contrary, Airtraq was functionally unique in providing good laryngeal exposure in the difficult setting and without excessive tongue compression.
authors.affiliation: Department of Anaesthesia, Warrington and Halton NHS Trust, Lovely Lane, Warrington, WA51QG, UK. sdarshane@sky.com
authors.forename: Seema
authors.initials: S
authors.lastname: Darshane
authors.forename: Mohiidin
authors.initials: M
authors.lastname: Ali
authors.forename: Sethuraman
authors.initials: S
authors.lastname: Dhandapani
authors.forename: Peter
authors.initials: P
authors.lastname: Charters
mesh_terms: D018592:Cross-Over Studies; D004867:Equipment Design; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation* / Q000379:methods; D020704:Laryngoscopes; D007828:Laryngoscopy / Q000379:methods*; D008348:Manikins; D008954:Models, Biological; D014059:Tongue