Predicting difficult intubation with indirect laryngoscopy

Anesthesiology. 1997 Feb;86(2):316-21. doi: 10.1097/00000542-199702000-00007.


Background: It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult.

Methods: Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity.

Results: Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01).

Conclusions: Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.

MeSH terms

  • Adult
  • Aged
  • Female
  • Humans
  • Intubation, Intratracheal* / adverse effects
  • Laryngoscopy
  • Male
  • Middle Aged