The Likelihood of a Difficult Intubation

by Joseph Esherick, M.D., FAAFP, FHM

A recent article in JAMA reviewed 62 high-quality articles to determine the clinical factors that can help to predict the patient with a difficult airway.  Airway management experts have devised different scoring systems and exam findings that can predict the anatomically difficult airway; however, some patients with anticipated difficult airways turn out to be relatively straightforward intubations and others felt to be "easy airways" are more challenging in retrospect.  These investigators reviewed 62 studies with over 33,500 patients of which 10% were difficult intubations and concluded that the following factors increased the odds of a difficult intubation (Cormack-Lehane grade of 3-4:

  • History of difficult intubation - positive LR = 16
  • Class 3 Upper Lip Bite Test (lower incisors cannot extend forward to bite the upper lip) - positive LR = 14
  • Short hyomental distance <5.5 cm or three fingerbreaths - positive LR = 6.4
  • Retrognathia (distance from angle of jaw to tip of chin <9 cm) - positive LR = 6
  • Wilson's airway score ≥ 8 - positive LR = 9.1
  • Mallampati score ≥ 3 - positive LR = 4.1
  • Short intercisor distance <3 fingerbreaths (poor jaw opening) - positive LR = 3.6
  • History of snoring - positive LR = 3.4
  • Obesity with BMI>30 - positive LR = 2.2

This article is a great review for any clinicians involved in airway management whether you are practicing in the ER, ICU or responding to Rapid Responses or Code Blues on the hospital wards.

Endotracheal intubation course

Reference:  Will This Patient Be Difficult to Intubate? The Rational Clinical Examination Systematic Review by Michael E. Detsky, MD, MSHP; Naheed Jivraj, MBBS, MSc; Neill K. Adhikari, MDCM, MSc; Jan O. Friedrich, MD, MSc, DPhil; Ruxandra Pinto, PhD; David L. Simel, MD; Duminda N. Wijeysundera, MD, PhD; Damon C. Scales, MD, PhD.  JAMA. 2019;321(5):493-503