Predicting Difficult Intubation

Written by Clay Smith

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History of difficult intubation is the biggest predictor of trouble intubating, followed by grade 3 upper lip bite and others.

Why does this matter?
Avoiding, or at least being prepared for, a can’t intubate/can’t ventilate scenario is extremely important when intubating in the ED. What are the best predictors things will go well…or poorly?

Predicting airway trouble ahead
This is a brass tacks systematic review of 62 studies, 33,559 patients.

The biggest predictors of a difficult airway were (quoted from article; = positive likelihood ratios):

  • History of difficult intubation = 16 – 19

  • Upper lip bite test grade 3 = 14

  • Shorter hyomental distance = 6.4

  • Retrognathia = 6

  • Combination of findings on Wilson score = 9.1

  • Impaired neck mobility = 4.2

  • Modified Mallampati score > 3 = 4.1

The biggest predictors of a successful intubation were the absence of the above features, with negative likelihood ratios of 0.42 – 0.85. That means the absence of history of difficult intubation or these signs is a pretty good but not a great discriminator of who will be an easy airway.

All of these studies were done in the OR and not ED, and most used Cormack-Lehane grade as the measure of a difficult airway, which is a limitation of this when applying it the the ED setting, though I think it still applies.

Factors predicting difficult endotracheal intubation. Acad Emerg Med. 2019 Jun 28. doi: 10.1111/acem.13824. [Epub ahead of print]

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Reviewed by Thomas Davis

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