The ASA Difficult Airway Algorithm
CA-1 · draft
CA-1 Bootcamp day 13. Authored from cited abstracts; every claim carries a PMID.
Not reviewed. This deck cannot be opened, downloaded or sent
until you approve it. Read every point and its source first — they were drafted
from search results, not from clinical judgement.
Before induction
The difficult airway algorithm you will see on the theatre wall is the 2022 practice guideline of the American Society of Anesthesiologists, written jointly with eleven other airway, paediatric, trauma, critical care and international anaesthesia societies, which is why colleagues trained abroad recognise the same structure you were taught.
When twelve difficult-airway guidelines were appraised against the AGREE II instrument by four independent reviewers, the 2022 American Society of Anesthesiologists document scored highest with a mean quality score of 83.1 per cent, so if you are going to memorise one algorithm's logic this is a defensible one to pick.
The first branch of the algorithm is awake or asleep, and the awake branch is safer than its reputation: across 37 randomised trials and 2045 patients with anticipated difficult airways, awake fibreoptic intubation failed in 0.59 per cent, caused a severe adverse event in 0.34 per cent, and killed nobody.
Make the first attempt the best attempt by choosing the device before you induce, because in a Cochrane review of 222 studies and 26,149 patients videolaryngoscopes of every design reduced failed intubation, and the benefit of hyperangulated blades was largest in patients whose airway was already known or predicted to be difficult.
Every branch of the algorithm is bought with oxygen, and how you preoxygenate changes how much time you have: in a network meta-analysis of 52 trials and 3914 patients, high-flow nasal oxygen with the patient head-up prolonged safe apnoea time by a mean of 291 seconds compared with a facemask in the supine position.
The supraglottic airway is the rescue that usually works and occasionally does not - difficult ventilation through one occurred in 0.5 per cent and placement failed outright in 0.2 per cent of 14,480 adults - and when it does not work you are at emergency front-of-neck access, where in a wet-lab simulation trained doctors reached oxygen in a median of 65 seconds by cannula and 90 seconds by scalpel-bougie, with far more outright failures in the scalpel arm.
Questions in the room
What would push you to intubate this patient awake rather than asleep?
You have had two good attempts and the view is grade 3. What has to change before attempt three, and who else is in the room by now?
You can neither intubate nor ventilate. Say out loud, in order, what you do in the next sixty seconds.
If your plan is to wake her up, what has to have been true about the induction drug you chose forty minutes ago?
Oral boards stem
A 58-year-old woman with a thyroid goitre, a Mallampati IV view, a thyromental distance of five centimetres and a hoarse voice is scheduled for a hemithyroidectomy. You are the CA-1 assigned to the room. Before you draw up a single drug, your attending asks you to talk through the decision the difficult airway algorithm asks you to make first, and then to say what your plan A, plan B and plan C are, who you would want in the room, and at what point you would stop trying and wake her up.
Sources
Apfelbaum et al., Anesthesiology 2022
PMID 34762729
Fritz et al., Otolaryngology - Head and Neck Surgery 2024
PMID 37538005
Cabrini et al., Anesthesia and Analgesia 2019
PMID 30896601
Hansel et al., Cochrane Database of Systematic Reviews 2022
PMID 35373840
de Carvalho et al., British Journal of Anaesthesia 2024
PMID 38599916
Saito et al., Anaesthesia 2015
PMID 26052860
Rees et al., Anaesthesia 2019
PMID 31165475
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