The incidence of airway problems depends on the definition used

Definitions currently used to describe airway difficulties are confusing, inconsistent, and may be misleading. To understand the "extent of the problem" better using three different definitions we examined the corresponding rates of airway difficulty in 3,325 consecutive adult patients who had direct laryngoscopy with tracheal intubation following induction of general anaesthesia.

Definitions were (i) poor view at laryngoscopy (GRADE 3-4) documented on modified diagrams of Cormack and Lehane; (ii) > or = 3 laryngoscopy attempts; and (iii) failure of direct laryngoscopy. The incidences of airway difficulty attributable to each definition were compared.

For the three definitions rates varied, 10.1% for poor view, 1.9% > or = 3 laryngoscopies, and failure 0.1%. For patients with a GRADE 3-4 view, 15.8% required > or = 3 laryngoscopies, but for those with > or = 3 laryngoscopies, 84.1% had GRADE 3-4 view. All patients with failed laryngoscopy had > or = 3 laryngoscopies and a GRADE 4 view.

This wide variation in defining the "extent of the problem" emphasizes the need for agreement of definitions and improved methods to document airway difficulties.