title: Force and pressure distribution using Macintosh and GlideScope laryngoscopes in normal airway: an in vivo study.
abstract: BACKGROUND
  Forces applied on oropharyngeal soft tissues by direct laryngoscopy may cause damage to the patients. The aim of this study was to measure the forces applied during the manoeuvres to achieve glottis visualization and tracheal intubation, comparing direct laryngoscopy and videolaryngoscopy in vivo.
  
  
  METHODS
  Thirty adult patients (ASA physical status 1 or 2, BMI between 18 and 30 kg/m2, no difficulty to intubate) were randomly and blindly assigned to one of two groups. Forces and pressure distribution applied during glottis visualization and intubation were measured using film pressure transducers, comparing Macintosh direct laryngoscope and GlideScope videolaryngoscope.
  
  
  RESULTS
  Fifteen patients from each group, all with Cormack-Lehane grade 1 view, were analyzed. Forces applied during the intubation with the GlideScope were significantly lower than forces applied with the Macintosh (8+4 N vs. 40+14 N, respectively, P<0.001). Considering the Macintosh laryngoscope, the minimal force applied for glottis visualization was significantly lower than the one applied for intubation (16+6 N vs. 40+14 N, respectively, P<0.005). When using the Macintosh laryngoscope, forces were concentrated mostly on the tip, whereas with the GlideScope forces' concentration in a particular area was not observed.
  
  
  CONCLUSIONS
  Our study shows that in patients with normal airways the GlideScope allows a view of glottis and permits a successful tracheal intubation applying lower force (significantly in intubation) as compared to the Macintosh laryngoscope. Also, the GlideScope probe distributes the forces more homogeneously to the tissue thus further reducing the potential for tissue damage.
authors: Department of Anesthesia, University School of Medicine Campus Bio-Medico, 00128 Rome, Italy. m.carassiti@unicampus.it
authors: M
authors: M
authors: Carassiti
authors: V
authors: V
authors: Biselli
authors: S
authors: S
authors: Cecchini
authors: R
authors: R
authors: Zanzonico
authors: E
authors: E
authors: Schena
authors: S
authors: S
authors: Silvestri
authors: R
authors: R
authors: Cataldo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects; D020704:Laryngoscopes; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D009960:Oropharynx / Q000293:injuries* / Q000502:physiology*; D011312:Pressure; D055815:Young Adult