title: Anatomic features of the neck as predictive markers of difficult direct laryngoscopy in men and women: A prospective study.
abstract: OBJECTIVE
  Difficult airway assessment is based on various anatomic parameters of upper airway, much of it being concentrated on oral cavity and the pharyngeal structures. The diagnostic value of tests based on neck anatomy in predicting difficult laryngoscopy was assessed in this prospective, open cohort study.
  
  
  METHODS
  We studied 341 adult patients scheduled to receive general anaesthesia. Thyromental distance (TMD), sternomental distance (STMD), ratio of height to thyromental distance (RHTMD) and neck circumference (NC) were measured pre-operatively. The laryngoscopic view was classified according to the Cormack-Lehane Grade (1-4). Difficult laryngoscopy was defined as Cormack-Lehane Grade 3 or 4. The optimal cut-off points for each variable were identified by using receiver operating characteristic analysis. Sensitivity, specificity and positive predictive value and negative predictive value (NPV) were calculated for each test. Multivariate analysis with logistic regression, including all variables, was used to create a predictive model. Comparisons between genders were also performed.
  
  
  RESULTS
  Laryngoscopy was difficult in 12.6% of the patients. The cut-off values were: TMD ≤7 cm, STMD ≤15 cm, RHTMD >18.4 and NC >37.5 cm. The RHTMD had the highest sensitivity (88.4%) and NPV (95.2%), while TMD had the highest specificity (83.9%). The area under curve (AUC) for the TMD, STMD, RHTMD and NC was 0.63, 0.64, 0.62 and 0.54, respectively. The predictive model exhibited a higher and statistically significant diagnostic accuracy (AUC: 0.68, P < 0.001). Gender-specific cut-off points improved the predictive accuracy of NC in women (AUC: 0.65).
  
  
  CONCLUSIONS
  The TMD, STMD, RHTMD and NC were found to be poor single predictors of difficult laryngoscopy, while a model including all four variables had a significant predictive accuracy. Among the studied tests, gender-specific cut-off points should be used for NC.
authors: Department of Anaesthesiology, General Hospital of Rethymnon, Rethymnon, Crete, Greece.
authors: Chara
authors: C
authors: Liaskou
authors: Liaskou
authors: L
authors: Chara
authors: Department of Internal Medicine, George Papanikolaou General Hospital, Exohi, Thessaloniki, Greece.
authors: Eleftherios
authors: E
authors: Vouzounerakis
authors: Vouzounerakis
authors: V
authors: Eleftherios
authors: Intensive Care Unit, University General Hospital "AHEPA", Greece.
authors: Maria
authors: M
authors: Moirasgenti
authors: Moirasgenti
authors: M
authors: Maria
authors: Department of Anaesthesiology, George Papanikolaou General Hospital, Exohi, Thessaloniki, Greece.
authors: Anastasia
authors: A
authors: Trikoupi
authors: Trikoupi
authors: T
authors: Anastasia
authors: Department of Anaesthesiology, Aretaieion Hospital, School of Medicine, Athens, Greece.
authors: Chryssoula
authors: C
authors: Staikou
authors: Staikou
authors: S
authors: Chryssoula
keywords: Height-to-thyromental distance ratio; laryngoscopy; neck circumference; sternomental distance; thyromental distance