The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation

Anesthesiology. 1997 Dec;87(6):1290-7. doi: 10.1097/00000542-199712000-00005.


Background: A quantitative scale of intubation difficulty would be useful for objectively comparing the complexity of endotracheal intubations. The authors have developed a quantitative score that can be used to evaluate intubating conditions and techniques with the aim of determining the relative values of predictive factors of intubation difficulty and of the techniques used to decrease such difficulties.

Methods: An Intubation Difficulty Scale (IDS) was developed, based on parameters known to be associated with difficult intubation. It was then evaluated prospectively in a group of 311 consecutive prehospital intubations and 315 intubations in an operating room. In the operating room, the IDS was compared with two other parameters: the time to completion of intubation and the visual analog scale (VAS). Time was measured by an independent observer. Operators in both groups completed a checklist regarding the conditions of intubation.

Results: There is a good correlation between the IDS scale and the VAS assessment of difficulty and time to completion of intubation. VAS and time to completion have a significant but lesser correlation to each other. Comparison of IDS with operator-assessed subjective categorical impression of difficulty by Kruskall-Wallis was statistically significant.

Conclusions: The IDS correlates with but is less subjective than the VAS and categorical classification. IDS correlates with time to intubation, but it offers details regarding the difficulty encountered that time alone does not. This score may not only aid in evaluation of factors linked to difficult intubations, but it may provide a uniform approach to comparing studies related to this subject.

Publication types

  • Comparative Study

MeSH terms

  • Emergency Medical Services
  • Evaluation Studies as Topic
  • Humans
  • Intubation, Intratracheal / classification*
  • Intubation, Intratracheal / methods*
  • Operating Rooms
  • Pain Measurement
  • Prospective Studies
  • Time Factors