When the going gets tough – comparing tools in difficult airways

Difficult airways in kids might be mostly predicted but that’s not the end of them being difficult. How do we go with the tools we choose? By Andrew Weatherall

Kids’ anaesthetists spend a lot of time drawing bows of varying lengths. There is an awful lot of time spent reading a variety of things about adults and then trying to figure out how to alter their dimensions to fit the smaller types we’re dealing with.

And I’m sure adults have some positive features. I mean there are a lot of heroes putting cat vids on the internet.

It’s just that we really need to read things specifically about kids. Those papers come along. Eventually. And when they do it’s doubly important we pay some attention.

Which is why the PeDI registry and the things being popped out are worth looking at.

It’s a Big Database

30 + centres. 1295 cases of difficult intubation analysed. Those are pretty big numbers. The first paper from the registry looked at the formation of it with a little about complications during intubation. They then went on to look at comparative success rates with videolaryngoscopy compared to intubation with a bronchoscope through a supraglottic airway. Turns out in those ones kids under 10 kg and less than 1 year old were tricky.

This time they’re back for more on difficult intubation. The definition of difficult intubation is pretty well laid out here. A consultant anaesthetist has to be at least a bit involved and then you look for the following:

  • Children with a Cormack and Lehane view of 3 or above on direct laryngoscopy as per that consultant [sidenote Cormack and Lehane just isn’t that ace but let’s put a pin in that and come back another day].
  • Kids were you couldn’t even pull off direct laryngoscopy.
  • Kids who’d failed direct laryngoscopy within the preceding 6 months.
  • Kids where the consultant anaesthetist went with some variant of “yeah, let’s bugger the direct laryngoscopy off because that way madness lies”.

Now some patients just had a single attempt tried (either direct laryngoscopy or GlideScope) and some patients had one of those plus another (sometimes the other or sometimes another device entirely).

So 510 patients had just the one thing tried. 785 had more than one device tried.

So would you ordinarily have one look with the DL? Are you VL all the way? Well let’s see what the survey says.

The Horrifying Lowdown

Yes. Horrifying.

At first glance it’s a world of hurt for direct laryngoscopy. 10.2% of direct attempts (176/1731) were successful. For first pass success it’s 4%.

That’s it. Shut it down. Burn your direct laryngoscope, inhale the fumes and let the madness the molten metal creates bring you constant pain for ever having thought you’d use this device.

Except to be honest the GlideScope success rates are pretty grim too. 52.5% of attempts overall were successful and eventually 82% of patients were successfully intubated when a GlideScope was chosen. 21% of the patients eventually had successful ensnorkelling manoeuvres when DL was used.

That’s it then. Better go start work as a human statue to raise the money for the fancy screen.

Wait one minute now…

Except there’s a little more nuance to be mentioned.

1. Rates were a little different in the singles

Where a single device was used the initial success rate for direct laryngoscopy was 16% (but still way better in the GlideScope group at 66%). Was there a subset of those patients who had different findings? Who knows, because we can’t tell from this data set.

2. It’s not apples and apples

I’m not talking about the devices here. It’s the patients. Look at those ages in Table 1 (for the single use group). The average age in the GlideScope group is 8.1 but it’s 2.1 in the direct laryngoscopy group.

I mean the rates are still drastically different but patients that are 4 times as old (the GlideScope group) have at least a bit of a chance of not being the same. No amount of multivariate checking is going to put my mind entirely at ease on the question of whether we are comparing like with like.


It’s like we’re comparing apples with … actually I don’t know what that thing is in the background.

We’re also not talking about the same anticipation prior to getting into it. The Glidescope group (for the single device analysis) had an anticipated difficulty rate of 95%. For DL it’s 34%.

For the real world clinician there are two obvious points here:

  • Assessment makes a difference to what you do and how you approach things.
  • The majority of intubations are not tough so you are likely to be fairly relaxed. Until it is actually different. And now you go back and do the optimising steps you would have ideally set up if you anticipated difficulty. That’s a different story to 95% of patients where you’re preparing for the worst.

3. 100% is 100%

After all the chat the simple fact is that the direct laryngoscopy group (in the single device data) still had a 100% eventual success rate.

4. The under 10s

If you’re under 10 kg this analysis has well wishes to extend – good luck. The eventual success rate  is 82% with Glidescope overall (and 53% first pass success) but only 73% eventually in kids under 10 kg with an initial success in the 39% range.

I mean never work with kids and animals they say but these are tough numbers.

4. All of these rates are just not that great

Let’s put aside for a second that there are a variety of other devices not assessed here and just look at those rates.

An initial successful intubation rate of 53% for GlideScope videolaryngoscopy is extremely not ace. I mean 4% in the DL group is enough to have chanting monks wailing in jarring atonal harmonies but let’s not pretend 53% is reassuring. The under 10 kg crew do even worse (as mentioned above).

That’s sobering. I mean we were going to burn the direct laryngoscope but it’s not like we can set up a shrine to the expensive camera wand that doesn’t even capture souls for all that cash.

So what practical things should we take from this?

I mean someone should write that down.

Oh wait, that’s my job.

The Bit Where I Remember to Make Some Practical Notes

It turns out that kids who are difficult are really fairly spectacularly difficult. So what practical points are there? Well there’s more than can just go in this post but as a starting point:

1. Focus on assessment

This is not neuro-rocketshippery but it turns out assessment counts. At least part of the issue with the direct laryngoscopy stats was that people were surprised. Assessing better lets you plan better. Not a surprise, but worth remembering.

2. Documentation also matters

When making a choice for what device to use it’d really help the next anaesthetist to sue the record to make it clear why that was your choice.

Documentation tells the story for the next person. When I’m reading that chart it’d be really useful for me to be able to tell what bag-mask ventilation was like, whether there were issues with functional changes during induction, what device you used to get that view and how the actual insertion of the tube bit was. Then I can plan.

Along the way someone should really indicate what the direct view is like too. If it turns out the direct view is lousy it’d be useful to know that (rather than just relying on me assuming that you chose the videolaryngoscope because it was previously lousy).

3. Videolaryngoscopy might not be the best choice

The real take away here might just be that for the difficult kids the debate might not be about videolaryngocope vs direct laryngoscope. I mean we should probably not persist with direct laryngoscopy where we predict true difficulty but there are better techniques than the camera. Converting a supraglottic airway to a tube or using bronchoscopy along with the videolaryngoscope are probably both things to reach for rather than just the GlideScope.

But we’ll have to get back to those another time.

There are  probably cat vids we should all be watching.



That image of the apple and the …. thing was from unsplash.com and was posted by Roberta Sorge.

The paper is this one (it’s still just an ePub at the moment I think):

Park R, Peyton JM, Fiadjoe JE, et al. The efficacy of GlideScope videolaryngoscopy compared with direct laryngoscopy in children who are difficult to intubate: an analysis from the paediatric difficult intubation registry. British Journal of Anaesthesia. [Epub ahead of print] https://doi.org/10.1093/bja/aex344

There’s a good editorial that goes with it:

Aziz M. Big data, small airways, big problems. British Journal of Anaesthesia. [Epub ahead of print] https://doi.org/10.1093/bja/aex362

The other papers from PeDI are these ones:

Fiadjoe JE, Nishisaki A, Jagannathan N, et al. Airway management complications in children with difficult tracheal intubation from the Pediatric Difficult Intubation (PeDI) registry: a prospective cohort analysis. Lancet Respir Med. 2016;4:37-48. 

Burjek NE, Nishisaki A, Fiadjoe JE, et al. Videolaryngoscopy versus Fiber-optic Intubation through a Supraglottic Airway in Children with a Difficult Airway: An Analysis from the Multicenter Pediatric Difficult Intubation Registry. Anesthesiology. 2017;127:432-40. 

Do you need a break after all that? Why not go and enjoy the simple zen of chemical reactions at a very personal level?



3 responses to “When the going gets tough – comparing tools in difficult airways

  1. Pingback: When the going gets tough – comparing tools in difficult airways — Songs or Stories | Prehospital and Retrieval Medicine - THE PHARM dedicated to the memory of Dr John Hinds·

  2. Pingback: Tough tools | Prehospital and Retrieval Medicine - THE PHARM dedicated to the memory of Dr John Hinds·

  3. Pingback: Looking Back Before Looking Forward | Songs or Stories·

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