Difficult airways can’t be reliably predicted

This paper1 proves what Rich Levitan has been saying (and writing) for years – that there is no method of prediction of difficult intubation that is both highly sensitive (the test wouldn’t miss many difficult airways) and highly specific (meaning those predicted to be difficult would indeed turn out to be difficult). Most importantly, this means one should always have a plan for failure to intubate and failure to mask-ventilate regardless of how ‘easy’ the airway may appear.

This study of a large prospectively collected database captured anaesthetists’ clinical assessment of likelihood of difficult intubation and difficult mask-ventilation, and compared them with actual findings. These studies are always difficult, due in part to the lack of standard definitions of difficult airways, but the take home was clear – the large majority of difficulties were unanticipated and not suspected from pre-operative clinical assessment.

This issue was brilliantly summed up by Yentis in a 2002 Editorial2:

I dare to suggest that attempting to predict difficult intubation is unlikely to be useful – does that mean one shouldn’t do it at all? To this I say no, for there is another important benefit of this ritual: it forces the anaesthetist at least to think about the airway, and for this reason we should encourage our trainees (and ourselves) to continue doing it.”

1. Diagnostic accuracy of anaesthesiologists’ prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database
Anaesthesia. 2014 Dec 16. doi: 10.1111/anae.12955. [Epub ahead of print]


Both the American Society of Anesthesiologists and the UK NAP4 project recommend that an unspecified pre-operative airway assessment be made. However, the choice of assessment is ultimately at the discretion of the individual anaesthesiologist. We retrieved a cohort of 188 064 cases from the Danish Anaesthesia Database, and investigated the diagnostic accuracy of the anaesthesiologists’ predictions of difficult tracheal intubation and difficult mask ventilation. Of 3391 difficult intubations, 3154 (93%) were unanticipated. When difficult intubation was anticipated, 229 of 929 (25%) had an actual difficult intubation. Likewise, difficult mask ventilation was unanticipated in 808 of 857 (94%) cases, and when anticipated (218 cases), difficult mask ventilation actually occurred in 49 (22%) cases. We present a previously unpublished estimate of the accuracy of anaesthesiologists’ prediction of airway management difficulties in daily routine practice. Prediction of airway difficulties remains a challenging task, and our results underline the importance of being constantly prepared for unexpected difficulties.

2. Predicting difficult intubation–worthwhile exercise or pointless ritual?
Anaesthesia. 2002 Feb;57(2):105-9

4 thoughts on “Difficult airways can’t be reliably predicted”

  1. Hi Cliff,

    Thanks for the post. A little surprised by the incredibly abysmal sensitivities & specificities from the Danish study. My personal experience doesn’t seem to correlate with these numbers. However, I do think the bottom line holds true: we are not that good at predicting difficult airways & certainly nobody could predict them all.

    I think the most important take home line from your post is this line:
    “Most importantly, this means one should always have a plan for failure to intubate and failure to mask-ventilate regardless of how ‘easy’ the airway may appear.” Couldn’t agree with you more; and this is why it’s not a problem that we’re not good at predicting the tough ones. All my residents know that when they intubate with me, I want everything they need for a potential difficult airway on a table right next to them (bougie, alternate blade, nasal/oral airways, end-tidal already hooked up to BVM, LMA, video back up, etc including the difficult airway cart in the room) for EVERY SINGLE INTUBATION. Everything needed is on my intubation checklist and we just quickly shoot down the list before we go. (Of course Tim will agree & Minh will beg to differ with the latter point!)

    So should we just quit assessing for potential airway difficulty prior intubation since we’re not good at it and we’re going to be well-prepared for the unexpected difficulty airway anyway? I completely agree with you- definitively no! Firstly, it works to heighten our awareness that the airways may be difficult. Secondly, (Rich in his genius at the “psyche of intubating” would certainly agree with this) more important than being prepared logistically, we MUST be prepared MENTALLY! Assessing the airway plays an important role w/respect to mental preparedness. Finally, if ya get to be as finessed as Keith Greenland at airways, you’ll realize that assessing for the difficult airways may become an integral part of formulating your attack on airway and tailoring it for your particular patient based on their specific anatomy.

    In summary: 1. We’re not good at predicting difficult airways. 2. Number 1 doesn’t matter if you logistically AND MENTALLY approach ALL airways as if they will be difficult. 3. Despite Numbers 1 & 2, we should always assess for difficult airway bc it will heighten our awareness to the difficult airway, mentally prepare us, and may aid in our approach to our airway attack.

    Best,

    -Sam

  2. Hi Cliff.

    I agree with Sam’s and your sentiment on the issue. It brings me back to watching Scott W’s Smacc talk on Surgical Airway….. “Always treat each patient as if they may need a surgical airway”. From my own prehospital and hospital experience, it has been a lifesaver having verbalised a Plan B & C pre intubation. Certainly in the ED i work in, our anaesthetic colleagues are on board with having the difficulty airway trolley present for every intubation and running through our checklist. I cant emphasise how important it is to visualise mentally performing a surgical airway and what a plan B/C would entail. I also found reading Cmdr Hadfield’s book ” An Astronauts guide to life on earth” a useful read with regards to the principals he learnt and used being applied to Emergency Medicine. He talks about how to prepare for the unexpected and the need to “Sweat the small stuff”
    Scott’s talk/podcast link is below.

    http://emcrit.org/podcasts/surgical-airway/

    KR

    Neel

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