R. V. Prasad, M.D., S. Dogra, FFARCSI, and T. E. Keogh, MD

Dept. of Anesth., Univ. of N. Carolina School of Medicine, Chapel Hill, NC  27599-7010

Background: A concise, reliable scale grading the difficulty of tracheal intubation could improve patient safety by facilitating the transfer of important information to future airway managers. Two of the authors had previously developed the Level of Difficulty of Intubation (LDI) scale (unpublished), which graded difficulty into four levels based on the actions necessary during intubation. The original scale was slightly modified for this study: (1) Straightforward intubation with direct laryngoscopy, no modifications to usual technique required. (2) Need to adjust patient position, reintroduce blade or apply laryngeal pressure. (3) Either a change of operator, or both a change of blade and another adjustment or technique were required. (4) Rescue techniques required, or impossible intubation. This study sought to test the validity of the LDI and each of its components by comparing it with two other ratings of difficulty: the Visual Analog Scale, VAS, and the Intubation Difficulty Score, IDS (1).

Methods: Data was prospectively collected in 817 intubations in a variety of in-hospital anesthetizing locations. The first operator attempting intubation completed a data sheet detailing the steps taken during intubation, and a VAS for difficulty of intubation. The LDI, IDS and VAS were then compared with each other.

Results: There was good correlation between the LDI and both the IDS (r=0.80) and the VAS (r=0.68). IDS also correlated with VAS (r=0.80).

Conclusions: The LDI correlates with both the IDS and the VAS. Compared to the IDS, the LDI is simpler to use. Furthermore, it provides more information about the actual process of intubation than either the IDS or the VAS. The LDI may improve patient safety by helping to guide future anesthesiologists in making decisions regarding the airway.

(1) Adnet F, Borron SW, Racine SX, et. al. The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology. 1997;87(6):1290-7.