Written by Clay Smith
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