Tag Archives: Airway

Airway, Paediatrics

Things that Go Up Kids’ Noses – THRIVE and Paeds

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Nasal prongs seem pretty popular for lots of things these days. So how about their use in kids. There’s a couple of papers out there on its use in the paralysed patient and Dr Andrew Weatherall is here to splice them together. 

Isn’t it supposed to be the kids who stuff things up their noses? Have we just seen them do it so often we started wondering about the possibilities ourselves?

Let’s assume not. It’s more a case of people finally getting around to testing things out on kids when they’ve been running with them in adults for quite some time. This time it is THRIVE and that ever so desirable feature of endless maintenance of oxygen saturations while we get around to the ensnorkelling we’ve planned.

In principle that makes plenty of sense. The normal kid is more likely to rapidly desaturate than the normal adult. Physiology is pretty insistent on that. Plus we know people find paediatric intubation tricky so dropping the stress by avoiding the slide of the plethysmograph tone down that digital scale is probably a worthy pursuit.

So how about we look at two papers examining just this issue – does THRIVE employed in the little people stop those saturations from … not thriving??

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Fancy, nose-cramming air is what we’re dealing with really

Australian Angles

First up is this paper published by Humphreys et al, who work out of Brisbane. They did a small RCT on well kids with 24 in the control arm and 24 receiving 100% THRIVE. The kids fell between the ages of 0 and 10 years of age and are reported in the age groups 0-6 months, 6-24 months, 2-5 years and 6-10 years (with a total of 12 in each age range, meaning 6 in the controls and 6 in the THRIVE group within each age group – got it?)

The routine went something like *induction of anaesthesia* –> pre-oxygenation by doing that whole bag-mask ventilation bit –> the mask disappeared and THRIVE was added or nothing was added –> start the stopwatch.

You’ll note that, like the other paper we’ll mention, this is not about patients who are spontaneously ventilating. That’s a completely different thing.

In this group though the period of the saturations staying up was longer. Across the age groups the extension in apnoeic time was 86.8 seconds (0-6 months), 88.7 seconds (6-24 months), 129.5 seconds (2-5 yeas) and 169.2 seconds (6-10 years).

Right, lock it up. Everyone should have nasal prongs. All the time. It’d stop peanuts ending up there too.

Except there’s more pesky nuance in this paper. Like:

1. It’s not for pre-oxygenation

It’s worth noting that the preoxygenation here was all about face-mask ventilation with a good seal. They added THRIVE after that bit and started the clock. This is not entirely surprising because we know that nasal prongs compromise seals in adults and that’s only more likely with kids.

So if you were thinking that you should set up those nasal prongs from the before time zero, you need to think again. THRIVE for preoxygenation is not something tested here, and you shouldn’t assume it’d be better than good face-mask technique.

2. They didn’t test the duration that it worked for apnoea

All they said was it’s ‘more’. ‘Wait,’ you might say, ‘you mean they didn’t test the thing that was the point of study?’

Well not really because the cut-off was ‘twice the previously noted time to desaturation’. So they tested that they could reach the ‘double or nothing’ limit, but didn’t test the full extension. In the THRIVE groups the average saturation when they stopped the clock was 99.6%.

So I guess be reassured that it was likely to be really a heck of a lot of time.

3. Basic things were part of the procedure

For this study there was a lot of basics being done well. Throughout apnoeic oxygenation they weren’t doing things like airway instrumentation, suction, intubation or, I assume, anything much beyond chatting about the weekend and watching the clock. They did jaw thrust, a basic manoeuvre likely to optimise the impact of THRIVE. So maybe we should remember that all those things we are also interested in were not part of the picture.

And Now an Update from the Swiss

What if you didn’t make your cut-off ‘2 times the other cut-off we knew about’? How long could you go?

Well a Swiss crew with no interest in being neutral on the topic I guess have done a study comparing low flow nasal oxygen (0.2 L/kg/min) with THRIVE at either 100% or 30% FiO2 with 20 in each group. And they found … (wait for it…..) 100% THRIVE prolongs apnoea time.

OK there wasn’t much suspense there really.

Except again it was more subtle, and again cut-off matters. They had a cut-off to terminate on the basis of desaturation, but another at 10 minutes (as in ‘it’s 10 minutes and I’m bored let’s stop because those saturations are still great’) and the 3rd cut-off was if the transcutaneous CO2 hit 65 mmHg.

In the THRIVE 100% group no one desaturated, 4 hit 10 minutes and the other 16 had their nasal prongs ditched when they breached the CO2 target. This actually accords with the other paper where they also found that THRIVE doesn’t achieve ventilation and removal of CO2 in kids.

But at the end of this paper you still can’t say how long apnoea might be extended, at least when it comes to those saturations staying up.

Oh, and a couple of other points:

1. Pre-oxygenation was with face-mask ventilation. Again.

Again the nasal option had no role in the preoxygenation phase. They went with face-mask ventilation until the expired oxygen was 90% or above. Then they started the clock with the chosen nasal prong option going.

2. The other airway things done at the time were … none.

Yep. Once again this was just about the oxygen and the stopwatch. Nothing else was going on.

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I mean this could be a visual metaphor for the need to appreciate their is still colour not just black and white when it comes to THRIVE or it could just be pretty, you choose. 

Let’s Think Clinically

So let’s imagine that we’ve actually got that paediatric patient in front of us. Maybe one who needs to get intubated before we get them out of wherever ‘in front of us’ is.

Let’s agree that maintaining oxygenation throughout is a good and noble goal. It’s not the only goal of course. We’d also like to make sure we make good choices around number of attempts, and for some patients (say the patient with intracranial pathology) we need to think about ventilation.

And we don’t have evidence that pre-oxygenation is aided by having THRIVE in place.

So assuming we’re going to do things standard to modern paediatric RSI like face-mask ventilation for a bit before we get going. There is at least a bit of  a question about whether THRIVE adds a huge amount.

What it undoubtedly adds is the confidence that saturations will stay up. That is something that lots of practitioners, particularly those not regularly intubating kids would find immensely reassuring.

There is a couple of caveats to keep in mind though.

There’s a risk to be aware of with THRIVE that those saturations staying interminably up might encourage tunnel vision on persisting with intubation when it’s not working out. It’s not too hard to imagine the scenario where the tube hasn’t passed straight down, but those saturations are OK so you persist a bit longer, and a bit longer, and now long enough that the airway is becoming traumatised and suddenly you’ve created a problem.

So this might be a cognitive challenge to have planned for in advance – how do you keep yourself to a limited number of attempts before re-evaluating and going to plan B (or C)? Do you make it a personal process or have others in the crew hold you to a maximum number of attempts or maximum duration of looking?

After all, THRIVE is going to get you to 10 minutes probably. But if you’re still conducting open negotiations with the glottic structures at 10 minutes, oxygenation is not the airway problem that should still be at the front of your mind. While you’re there, you might have to think about re-dosing anaesthetic agents too.

And the other key patient group is that one where intracranial pathology is an issue. Letting the CO2 rise for some patients is not a good plan because your TBI patient (as just one example) doesn’t need those cerebral vessels dilating and the intracranial pressure going up. For those patients, a step back to face-mask ventilation, or potentially placing a supraglottic airway,  to re-establish an ability to exchange CO2 is probably a better option.

So THRIVE might be great for some things. But whether it’s clinically better than an approach to the airway where really excellent pre-oxygenation is routine and good practices around face-mask ventilation are established seems like a line ball call.

I mean it’s still way better than a piece of Lego up the nose. But it remains an adjunct to the basic stuff, not a replacement.

Notes:

OK. That first paper is this one:

Humphreys S, Lee-Archer P, Reyne G, et al. Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) in children: a randomised controlled trial. BJA. 2017;118:232-8. 

The second one out of Switzerland is this one:

Riva T, Pedersen TH, Seiler S, et al. Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) for oxygenation of children during apnoea: a prospective randomised controlled trial. BJA. 2018;120(3):592-99.

Did you want something on nasal prongs and seals? You could try this

Groombridge C, Chin CW, Hanrahan B, Holdgate A. Assessment of Common Preoxygenation Strategies Outside of the Operating Room Environment. 2016;23:342-6. 

or this

Hayes-Bradley C, Lewis A, Burns B, Miller M. Efficacy of Nasal Cannula Oxygen as a Preoxygenation Adjunct in Emergency Airway Management. Ann Emerg Med. 2016;68:174-80.

We’re always interested in other thoughts so feel free to drop a comment.

Airway, intubation, Prehospital Trauma

Just because you can …

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With a couple of new papers landing that touch on the issue of how you provide and measure quality care around airway management, Dr Alan Garner returns to point at big animals that are bad at hiding.

Two new airway papers have come across my desk in the last couple of weeks and I now wish I had waited a bit longer before putting up the last post on first look intubation as a quality measure.

So where to start? Well how about a place where everything is apparently big? Yes, there’s a bit of work just out of Texas which sheds further light on that first look intubation story so that’s where we’ll land.

Chasing Quality

It sounds like they have used RSI for a while but undertook a quality improvement project to try and reduce their peri-intubation hypoxia rate.  The project involved introducing a bundle of interventions described in the paper as “patient positioning, apn[o]eic oxygenation, delayed sequence intubation, and goal-directed preoxygenation”.

The paper provides copies of the protocol for intubation pre- and post-bundle intervention in the on-line appendices so I might just go through them here to see what they did differently.

The first thing is there was an emphasis on positioning in the bundle, specifically head up a bit and ear-sternum positioning.  Lots of goodness here that I strongly support.

The second measure they mention was apnoeic oxygenation.  However looking at the pre- and post-bundle policies it is evident that they used it in both time periods.  In the before period it ran at 6L/min till the sedation was given then it was turned up to 15L/min.  In the post period however it was run at “MAX regulator flow” after the ketamine was administered.  I don’t know about the O2 regulators in Texas but to me this does not sound like they changed anything significant.  I will come back to apnoeic oxygenation later.

For pre-oxygenation in the pre- bundle period they used a NRB mask (with nasal prong O2 as above) in spontaneously ventilating patients (and arrested patients were excluded) but in the post- period the pre-oxygenation had to be by BVM with two handed technique to ensure a tight seal plus PEEP.  More goodness here that warms my heart.

Delayed sequence intubation in this study refers to administering 2mg/kg of ketamine then maximising preoxygenation for at least 3mins prior to administration of the muscle relaxant.  I don’t think this is necessary in all patients but this was the policy in the bundle.

The last thing they did was “goal-directed preoxygenation”.  This refers to having a SpO2 target >93% for at least 3 minutes during the pre-oxygenation phase after the ketamine had been administered.  If they could not achieve >93% the patient was managed with an LMA or BVM and transported.  I think this represents sensible patient selection in that it removes the high risk of desaturation patients from the process.  When you look at the results you need to keep this patient selection in mind. However I agree that in their system this is a reasonable approach to ensure patient safety for which the managers should be applauded.

Show Me The Money

Yes let’s get to that money shot:

Table

I have been banging on about peri-intubation hypoxia being far more important than first look intubation rate for a while now and this data shows really clearly why.

There is no significant difference in this study in either first look or overall success rates pre and post the bundle but the hypoxia rate fell by a massive absolute 41%!  The 16% decrease in bradycardia emphasises just how much difference they made.  The managers of this system and their staff alike both need to be congratulated for this achievement as this is something that really matters.  And the first pass and overall success rates give no clue!

It really is time to drop first look as a quality measure and move on.  You could look at this paper and start wondering if it might even be worth dropping overall success rate too, which is an interesting thought.  Their policy favoured patient safety over procedural success rates by abandoning the attempt if the pre-oxygenation saturations could not be raised above 93%. It looks like it is working out well for the patients.

Oh, Back to Oxygenation

I promised I would come back to the apnoeic oxygenation issue.  I know the authors state that it was part of their bundle, but it was used in the pre- bundle period as well.  Hence there is no data here to support it’s use.

All three randomised controlled trials of apoeic oxygenation in the ED and ICU contexts (see the notes at the end) have now failed to find even a suggestion that it helps (check those notes at the end for links) and there are no prehospital RCTs.  My take is that it is time to move on from this one too and simply emphasise good pre-oxygenation and good process when the sats start to fall – or never rise in the first place like this group did so well.

Overall a big well done to the Williamson County EMS folks and thanks for sharing your journey with us.

Moving Right Along

The other paper comes out of London, where the ever-industrious HEMS group have published a retrospective review of their database over a 5 year period (from 2009-2014). They were looking for adult trauma patients they reached with an initial noninvasive systolic blood pressure of 90 mmHg or less (or where a definite reading wasn’t there, those with a central pulse only) and with a GCS of 13-15.

This gave them a total of 265 patients (out of a potential 9480 they attended). 118 of those underwent induction of anaesthesia out there beyond the hospital doors (though with exclusions in analysis they end up with 101 to look at) and the other 147 (that number dropped to 135 on the analysis) got to hospital without that happening.

Now the stated indications for anaesthesia listed are actual or impending airway compromise, ventilatory failure, unconsciousness, humanitarian need, patients unmanageable or severely agitated after head injury, and anticipated clinical course.

Now given that the inclusion criteria includes patients having a GCS of 13-15, it seems like both unconsciousness and those really impossible to handle after head injury are likely to be pretty small numbers in that 101. Even airway compromise, ventilatory failure and humanitarian need seem like they’d be not the commonest indications in that list that would apply to this patient group, though they’d account for some.

I guess it’s possible the patients were all initially GCS 13-15 on the team’s arrival but deteriorated en route, though I just can’t sift that out from the paper. Plus if that was the case it seems like you’d say that.

The Outcomes

In their 236 study patients, 21 died and 15 of those were in the ‘received an anaesthetic’ group. The unadjusted odds ratio for death was 3.73 (1.3-12.21; P = 0.01). When adjusted for age, injury mechanics, heart rate and hypovolaemia the odds ratio remained at 3.07 (1.03-9.14; p = 0.04).

Yikes, sort of.

What To Make of That? 

I guess we should make of it that … things you’d expect to happen, happen? Intubating hypotensive patients and then adding positive pressure ventilation in the prehospital setting is potentially risky for patients for a variety of known pharmacological and physiological reasons that the authors actually go into.

So the question is why embark on such a procedure where you know the dangers in detail? You’ve have to really believe in it to end up wiht 101 cases to follow up.

It feels like there’s an elephant in the room to try and address by name. I wonder if it has something to do with a practice I observed while working in the south-east of England 8 years ago. It relates to that last category “anticipated clinical course”.

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Hovering elephant heads. They’re real.

The concept here is that if you figure the patient is going to be intubated later on in the hospital, you might as well get on and do it. Except the data here suggests that, much like you’d expect, you probably shouldn’t get on and channel your inner Nike marketing script.

Just because you can does not mean you should.  This paper really drives this home though it doesn’t really seem to come straight out and say it. It does pass the comment that “Emergency anaesthesia performed in-hospital for patients with cardiovascular compromise is often delayed until the patient is in theatre and the surgeon is ready to proceed.” Perhaps the problem isn’t using the phrase “anticipated clinical course”. It might be that you just have to remember that the anticipated course might best contain ‘risky things should probably happen in the safest spot’ in the script.

Compare and Contrast

The process of undertaking emergency anaesthesia because later the patient might require emergency anaesthesia is pretty much the complete opposite of the approach from the Williamson County EMS folks. They erred on the side of patient safety and withheld intubation if it was associated with unacceptable risk.

This paper demonstrates that emergency anaesthesia in patients with a high GCS but haemodynamic instability is associated with higher mortality.  We should probably be glad the authors have made this so apparent, because this is probably as good as we’re going to get. We’re not going to get a randomised controlled trial to compare groups. No one is allowing that randomisation any time soon making this another example of needing to accept non-RCT research as the best we’ll get to inform our thinking.

Patients with hypovolaemia due to bleeding need haemorrhage control. The highest priority in patients with that sort of hypovolaemia would seem to be getting them to the point of haemorrhage control quicker. And delaying access to haemorrhage control (because the prehospital anaesthesia bit does add time in the prehospital setting) when the patient has a GCS of 13-15 doesn’t seem to prioritise patient safety enough. Patients probably need us to adjust our thinking on this one.

That seems like common sense. The retrospective look back tells us pretty conclusively it’s a worse option for patients. And now it’s up to us to look forwards to how we’ll view those indications for our next patients. And “anticipated clinical course” probably just doesn’t cut it.

 

Notes:

That hovering elephant head was posted by James Hammond in a Creative Commons-like fashion on unsplash.com and is unchanged here.

How about all those things that got a mention above that you should really go and read for yourself?

Here’s that whole bundle of care paper out of Texas:

Jarvis JL, Gonzales J, Johns D, Sager L. Implementation of a Clinical Bundle to Reduce Out-of-Hospital Peri-intubation Hypoxia. Ann Emerg Med. 2018;doi:10.116/j.annemergmed.2018.01.044 [Epub ahead of print]

Those RCTs of apnoeic oxygenation in critical care environments mentioned are these ones:

Caputo N, Azan B, Domingues R, et al. Emergency Department use of Apnoeic Oxygenation Versus Usual Care During Rapid Sequence Intubation: A Randomized Controlled Trial (The ENDAO Trial). Acad Emerg Med. 2017;24:1387-1394.

Semler MW, Janz DR, Lentz RJ, et al. Randomized Trial of Apnoeic Oxygenation during Endotracheal Intubation of the Critically Ill. Am J Respir Crit Care Care Med. 2016;193:273-80.  

Vourc’h M, Asfar P, Volteau C, et al. High-flow nasal cannula oxygen during endotracheal intubation in hypoxemic patients: a randomised clinical trial. Intensive Care Med. 2015;41:1538-48.

And that paper on the hypotensive, awake prehospital patients scoring an anaesthetic is this one:

Crewdson K, Rehn M, Brohi K, Lockey DJ. Pre-hospital emergency anaesthesia in awake hypotensive trauma patients: beneficial or detrimental? Acta Anaesthesiol. Scand. 2018;62:504-14.

 

 

 

 

 

 

 

 

 

Airway, Practical Things

I Wish I Knew Then What I Know Now: Simple Airway Management

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This is a popular series and it’s not hard to see why. Greg Brown drops back in to talk about the airway device that is now his go to item. 

I clearly remember a time when the escalation of airway management in prehospital care resembled the fabled Underpants Gnomes from South Park and their three step plan to making a profit.

Back then, airway management looked something like this (and yes there were four steps, not three like in South Park):

  1. Patient’s own airway – bummer; that’s no fun for anyone.
  2. Oropharyngeal airway (aka the Guedel) – fun but not that inspiring.
  3. Endotracheal tube – break out the high fives, it’s a good day to be a medic.
  4. Needle cricothyroidotomy – if an ETT doesn’t do it, a 14 gauge cannula in the throat ought to fix it. Then there are the mutual backslaps.

Back in the day when I was new to military prehospital care (and at a time where not much was happening in the world) the focus seemed to be on big ticket items and not the purpose of the interventions. Indeed, it seemed to me that the drug of choice for any airway problem was plastic; and the bigger the problem, the smaller the dose.

What I know now is that the one’s choice of procedure must consider a whole lot more than just self-gratification. Airway problems are generally either an oxygenation or a ventilation issue, and the choice of procedure must take at least this into account. However, the purpose of this post on the Collective is not to discuss the differences between CICV and CICO (nor the relative advantages of DL vs VL) but simply to discuss basic airways.

Simple Is As Simple Does

There is no doubt that a patent airway that was issued to the patient at birth is best for the patient. Therefore, it goes without saying that anything that can be done by the treating professional to maintain a patent natural airway should be at least considered. I am not going to go into how best to clear an airway and position a patient as there are a myriad of reputable sources out there for you to conduct your own research but I will make two important points:

  1. In a perfect world the “ideal” position will align (and therefore open) the upper airway; seemingly minor changes in positioning can have significant detrimental impacts on airway potency (and vice versa); and,
  2. If you don’t know how to position a patient or provide manoeuvres then you might want to consider taking a step back and booking into a first aid course. Quite quickly. Like right this second. Just do it ….

Still here? Good then, on with the show.

Which means it’s time to introduce one of the heroes: a simple artificial airway. To Guedel or not to Guedel? For many years that has been the question, and the oropharyngeal airway (OPA) was definitely my plastic of choice. Simple to insert and effective – two of my favourite things in a medical device. But are they deserving of their historical gold medal for simple airway adjuncts? Well, maybe yes and maybe no.

You see when it comes to simple adjuncts I have become, over the years, a massive fan of the nasopharyngeal airway (NPA). I would argue that they are just as simple to use as their orally inserted cousins – the operator just needs to be trained in their use. And whilst there are pros and cons to all medical interventions in my mind the NPA has one big benefit over the OPA – when (if) the patient starts to rouse the NPA can stay in, a handy thing for those pesky patients whose level of consciousness ebbs and flows.

Over the last ten years the NPA has gained popularity amongst first responders with thanks to support from some international heavy hitters, and not before time. You see, the NPA was actually invented before the OPA – 38 years earlier, in fact, by Joseph Clover of the Royal College of Surgeons (he later became a founding member of the Royal College of Anaesthetists) in 1870. The first OPA was designed by…. wait for it… Frederic Hewitt in 1908. The first “Guedel” was not even invented by Arthur Guedel whose name is now synonymous with the device. He didn’t enter the scene until the 1930’s (but I will grant that he made huge improvements to Hewitt’s rudimentary designs).

However, it was not until 2002 and the widespread introduction of Tactical Combat Casualty Care (TCCC) in militaries worldwide that the NPA started gaining favour once more. With thanks to a push from the United States Department of Defense’s Special Operations Command, NPA’s started making their way into the individual first aid kits of soldiers, sailors and airmen employed in combat operations. Indeed, by 2008 every Australian serviceperson employed in combat roles carried an NPA in a pouch alongside appropriate haemorrhage control devices. NPA’s are now taught as part of C-TECC guidelines (the civilian version of TCCC) and are now commonly the first artificial airway device reached for by those employed in first responder roles worldwide.

Table

Are there risks associated with the of an NPA? Well, this is medicine, isn’t it? Of course there are risks. The big one that everybody immediately jumps to is in the patient with suspected basal skull fracture (or a fracture of the cranial vault). The risk in inserting an NPA here is that the tube may indeed enter the cranial cavity instead of heading into the nasopharynx. But a review of the literature reveals only two cases where this occurred thus making it a rather extreme reason to be afraid of using an NPA. (Note: that same review of the literature also revealed an article advocating the use of nasopharyngeal airways in the treatment of watery diarrhoea…. Four words: single use only please!)

Putting It To Work

So how do you utilise an NPA (and I’m talking about as an airway device, not in treating diarrhoea of any consistency)? Well firstly, size matters. I am sure that at some point you, like me, have taught various methods. The first common method is to look at the diameter of the patient’s pinky finger – in theory, this is the same diameter of the nares (nasal openings). Therefore the NPA of choice should be the diameter of the patient’s pinky. Yes?

Alternately, the second common method of sizing pertains to length – in theory the distance from the nostril of choice to the tragus (that flap at the front of the ear where it meets the cheek) is the same as from the tip of the nose to the upper pharynx. Yes?

Well, research by Roberts et al in the EMJ found that a combination of the two methods is required to get reach NPA nirvana and that in fact the patient’s height was a better determinant of requisite NPA size. They used data from MRI scans to determine that, all things considered, the law averages reigned supreme. Average height male? Size 7.0mm Portex NPA. Average sized female? Size 6.0mm NPA. Or, you could await the rollout of the MRI App on your smartphone of choice…

Once you have selected the correct size NPA you simply pick the largest nostril, lubricate the outside of the NPA (the patient’s saliva is usually sufficient) and insert whilst aiming for the patient’s ear (the same side as the nostril you are using). By aiming for the ear you are pushing backwards, not upwards, thus reducing the risk of the NPA entering the cranial vault in that patient with a suspected basal skill fracture. For this reason the presence of a suspected basal skull fracture has relegated to the status of relative contraindication (no longer an absolute contraindication). If any significant resistance to insertion is felt then the attempt should be aborted and the other nostril attempted.

Be sure to consider how you will secure the NPA. Certain members of society have naturally wider nares and I’ve seen them inhale their NPA. Placing a large safety pin through the shaft of NPA just below the flange decreases the chances of this happening, but in most patients I’ve treated the safety pin has not been necessary.

 

So there you have it – another thing that I know now that I wish I knew then is that the NPA is not an evil device guaranteed to lead any patient who has ever experienced a blow to the head on a one way trip to the morgue. Rather, the NPA is now my simple airway of choice, an intervention that I have used countless times both on battlefields and in emergency departments, and is the only airway device that I carry on every single job. Oh, and it also has some purpose in treating patients with watery diarrhoea…apparently.

 

Notes:

Remember if you like things on this site there’s a box somewhere where you can throw your email address so you get a regular email when a new post hits.

Want to know about how your choices of airway adjuncts can affect ventilation? Then go here.

Interested in reading more about the facts and myths of NPA’s? Try this.

Here’s a cool little video about airway manoeuvres and simple adjuncts from that good crew at Life in the Fast Lane.

And a previous post that included the use of NPA’s in the tactical environment can be found here.

 

Airway, Paediatrics

The Dangerous Little Details

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A new bit of research is out looking at paediatric intubation in the prehospital and retrieval setting. Picking it up and turning it this way, that way and all around, here’s Dr Andrew Weatherall. 

Advanced prehospital practitioners that I’ve met have some pretty common traits. They are pretty comfortable around things that other people might find chaotic. They often have pretty strong opinions on food and coffee. Not necessarily even on good food either. I’ve been given connoisseur-level education on various take away options. Most importantly, they are appropriately bananas about doing a good job for their patients.

That extends to paediatric patients which is obviously excellent. Except we tend not to do our most excellent work when it comes to kids. The reasons for that could fill many a blog post (and maybe we’ll get back to that another time) but kids tend to get less pain relief when faced with similarly painful situations, less interventions even when they’re indicated and we tend to do those procedural things less well.

In 2011 Bankole et al. compared interventions in kids (defined as < 12 years old) and adults with a head injury and a GCS < 15 in New Jersey (there was 102 patients in the kids group matched to 99 adults with equivalent injuries).  69.2% of the kids had some sort of problem with intubation. That was across failed intubation (29.03% vs 2.27% in adults), tube dislodgement (16.12% vs 2.27%), wrong-sized tube (7.45% vs 0%) and multiple attempts (as in over 3 tries) at intubation (6.45% vs 2.27%). A peripheral IV was there in 85.9% of adults but only 65.7% of kids.

In a paper that also commented on relative intubation rates in advanced EMS vs general EMS in the Netherlands, Gerritse et al also commented on analgesia. In their study 77% of kids who really needed some form of analgesia actually received nothing from the general EMS. No kid under the age of 4 received any form of analgesia from the EMS. Not one.

I’m not quoting those papers to say anything other than good practitioners (I have a predisposition to think most of those working at any level of EMS are people trying to do the best job their system and training allow) find kids extra difficult. This patient group provides an additional challenge on top of the storm you already deal with the scene. Like someone started blasting fairy floss into your eyes in the middle of that storm. OK I’m not sure that was the greatest analogy but it’s happened now so maybe we can just agree to move on while also remembering that when you’re a kid fairy floss is pretty great. Mmmm, fairy floss.

Enter the Swiss, purveyors of good chocolate and cheese with holes, with some interesting work that sheds a little extra light on things that even the most advanced practitioners find challenging about little people and airway management.

Let’s Stop and Check the Scenery

Not the mountains or lakes or Large Hadron Collider scenery, the other scenery.

Appearing in SJTREM, the paper comes from a  look at their database between June 2010 and December 2013. Across their 12 bases and one affiliate base they do around 11000 prehospital or interhospital missions per year with their paramedic-doctor teams. I should point out that these advanced teams really have had good training in airway management and specific paeds time. The study looks at any kid under the age of 17 requiring any airway manipulation (not just intubation or supraglottic airway or tracheostomy but bag-mask ventilation as well).

From their pool of 4505 paediatric patients over the 3.5ish years (which if they’re doing around 11000 jobs per year should be around 11-12% of their total workload) the ended up with 425 kids requiring some sort of airway care (9.4% of the paediatric group). A little over half (225) were prehospital cases. From here on in when we talk about intubation it’ll be about prehospital missions because those moving between buildings were already intubated and ventilated.

So what did these top operators find?

Actually It’s Not About the View

In the 215 patients for whom an attempt at endotracheal intubation was attempted, first-pass success was 95.3%. Now, if you’ve dropped by this blog before you might recall Dr Alan Garner discussing whether this is the most important measure. I think that’s a great post, but I don’t think it is meant to be interpreted as “first pass intubation tells us nothing” (Alan can always correct me).

What this number does say is that the challenges in kids aren’t necessarily about getting a view of the cords that is enough to achieve intubation. Only 10 patients (4.7%) were described as inflicting a difficult airway management scenario on the team. 98.6% eventually ended up with a support snorkel in their trachea.

There were 2 children who could not be intubated and ended up oxygenating very nicely with the aid of a supraglottic airway, while one patient with a known “airway issues syndrome” (Goldenhar’s syndrome) couldn’t be either intubated or ventilated but was already at the end of a prolonged arrest situation.

So for advanced EMS providers, maybe it’s not the getting a view/passing the tube part of the procedure that is really at issue. In our own research that touched on this, the intubation success rate was 98.7% of the paediatric patients were successfully intubated while one patient was managed with a laryngeal mask in the prehospital phase.

This fits with the overall truth of paediatric airways: unanticipated difficult laryngoscopy is less common in kids than adults.

So Where’s the Problem?

The problems with paeds airway intervention here are about the details. You may have noticed that people who do subspecialty work in paeds can be a little bit fanatical about details. There’s a reason for this. A smaller airway is less forgiving of the tube that is the wrong size, be it too big or too small. An endotracheal tube that is 1 cm too far in on your 1 year old is proportionally a lot closer to the carina than when the same situation applies to an adult. Add a little flexion or extension and that whole tube can end up visiting new pockets of the bronchial tree.

This is the part that is really well covered in the Swiss study. In the 82.7% where intubation was noted, 82.5% got an adequately sized tube. It was too shrunken to be appropriate in 2.9% and too gargantuan in 14.6% (in the under 1s that rose to 57.5%). Rates were higher if that tube was placed during a CPR scenario.

The depth? Well, if you went off the formulae often mentioned in dispatches, most insertions were deeper than that. And while I can’t seem to find the bit in the results that clarifies this statement, the authors say in the discussion that “Only the placement of the depth marking of the correct Microcuff ET tube … for age between the vocal cords was accurate for all paediatric patients …” (Not familiar with the markings? You could look at an earlier post on this site, here.)

 

Details, Details

I think this is the key message of this study. Lots of things might make you sweat about paediatric airways. I suspect that for most practitioners it is the view and “plastic through the cords” components that cause the stress.

That bit is important, of course, and everyone wants to do that bit well. This study supports the argument that advanced practitioners already do that bit really well. Perhaps in thinking keenly about that bit it’s attention to some details, the sort of details that kids are pretty unforgiving about, that gets in the way of safer paeds airway management.

Stavros Markopoulos
Look at this butterfly. Gets fuzzy on the last few details of the right wing and can’t even butterfly properly.

Things to Take Away

Any research only reveals a very particular part of a story. There are questions left unanswered or things that don’t quite apply to your practice. That doesn’t mean we can’t use those results to reflect on things we do when we deliver our variant of advanced care.

So I’d say there are a few key things suggested by this study:

  • If you’ve trained in paediatric airway management, chances are the intubation itself (at least the getting a view and passing the tube bit) will go well.
  • Really well trained people still find the details challenging. The wrong tube size and the wrong depth of insertion matter in these patients.
  • It might be time to review whether those old formulae are the best option.
  • Knowing your equipment (like where the line on the tube goes) is pretty worthwhile.
  • The tube through the cords isn’t where attention to detail stops. That’s not the moment to ease up.

So we can all get out there, push through the fairy floss, be confident that we’ll get those endotracheal tubes in and start remembering the little details that will produce perfection.

No more fuzzy butterflies.

Notes:

Of course it’s not the fault of the butterfly it’s right wing looks fuzzy. It’s the photographer. Well, actually it’s an amazing photo where the wing is a tiny bit in a different alignment. It’s from flickr Creative Commons via Stavros Markopoulos and is  unaltered.

The source paper link is right here and it’s open access:

Schmidt AR, Ulrich L, Seifert B, Albrecht R ,Spahn DR, Stein P. Ease and difficulty of pre-hospital airway management in 425 paediatric patients treated by a helicopter emergency medical service: a retrospective analysis. Stand J Trauma Resusc Emerg Med. 2016; 24:22. 

I also mentioned a paper we put out there:

Barker CL, Weatherall AD. Prehospital paediatric emergencies treated by an Australian helicopter emergency medical service. 2014; 21:130-5. 

Then there’s the Bankole et al. paper:

Bankole S, Asuncion A, Ross S, et al. First responder performance in pediatric trauma: A comparison with an adult cohort. Pediatr Crit Care Med. 2011;12:e166-70. 

And finally the Gerritse et al. paper which is also open access:

Gerritse BM, Schalkwijk A, Pelzer BJ, Scheffer GJ, Draaisma JM. Advanced medical life support procedures in vitally compromised children by a helicopter emergency medical service. BMC Emerg Med. 2010;10:6.

Addit: After a really helpful comment from Paramedidad the line “In their study 77% of kids who really needed some form of analgesia.” was fixed to read “In their study 77% of kids who really needed some form of analgesia actually received nothing from the general EMS.” 

 

Airway

The Elephant in the Room: Airway Stuff for Non-Intubators

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Tim Wallace, emergency nurse, midwife and flight nurse from the Top End, returns to the blog with a different look at a popular topic – airway management. 

Some stuff to ponder for the non-intubators…

 Do you routinely assess, plan and prepare for airway issues in patients with a risk of airway compromise?

Could you honestly say you would be able to reliably manage A and B on your own?

Who does the work?

Emergency airway and ventilation management is routinely performed by a group of providers that it would be reasonable to call airway non-experts. This group includes paramedics, nurses, lifeguards and community first responders. Amongst these individuals there is significant variability in initial & ongoing training, experience and exposures to relevant simulated and actual airway/ventilation management.

A 2011 audit using data from 16 US states (Wang et al table 1) reveals 23% of interventions that could be classified as ‘critical care’ level, and while it is impossible to determine the skill level of the providers who performed the other 77%, it is reasonable to assume that they were not all critical care clinicians.

Conversely, the narrative and evidence base is dominated by the group who probably perform the lowest volume of work (the intubators). While I’m not arguing that we’ve heard the final word on interventions like pre-hospital RSI, I figured it was time to talk about the non-intubators, which for the purposes of this discussion I’m going to limit to paramedics and nurses – not necessarily novices and not necessarily inexperienced.

Whilst I have ignored endotracheal intubation (ETI) and those trained to do it as any casual observer will recognise the internet is bursting at the seams with content on advanced airway management. At times I get the impression from the blog/social media world that intubation (with ketamine) is some kind of panacea. If we glance over at the situation for our “occasional intubator” (typically medical or paramedic) who performs between 1 and 50 people per year (Reeves & Skinner 2008), there is  acknowledgment of and significant controversy in the state of affairs around procedural success and risk.

I think it’s reasonable that we apply the same scrutiny to the non-intubators.

Really Simple Things

Simple airway management and bag-valve-mask (BVM) ventilation are simple yeah?

I’ll try to avoid the term ‘basic airway management’ because I don’t really think it’s very basic; positioning, manoeuvres, suction, BVM, oral and nasal airways etc. I’ll also chuck in intermediate-advanced airways like LMAs (laryngeal mask airways) as we are generally all trained and expected to use them if required. 

Despite how these skills are represented in many courses and the common fallacy within the health system that completion of an Advanced Life Support course confers reliable competence in advanced life support (alluded to by Kidner and Laurence, 2006), it turns out in the hands of the less skilled/experienced operator, it can be very difficult to achieve airway control and maintain ventilation. Anaesthetists don’t really represent basic airway management as basic, so the rest of us probably shouldn’t either.

The Literature and BVM

Unsurprisingly, Walsh et al (2000) demonstrated anaesthetists were better at BVM ventilation than other doctors, supporting the notion that training, experience and exposures matter when it comes to this skillset. The evidence-based consensus (e.g. Otten et al, 2014) is that 2 handed (versus 1 handed C-grip) BVM technique is superior. However, while 2-person BVM (outside the OT) should be the stated aim, this is not an option on a nurse-only retrieval or in the back of a moving ambulance. Interestingly, in this experiment subjects with more experience bagging people in emergencies did not perform better than inexperienced subjects, though you would imagine this might change if you introduced a toothless bearded man with down syndrome into the mix.

In Noordergraaf et al’s useful 2004 study on real (anaesthetised) people, fire-fighters with 3 hours training on airway/ventilation management attempted to maintain airway patency and deliver BVM ventilation. Up to 23% of the time, they could not maintain an airway using BVM, simple manoeuvres and adjuncts. Additionally, half the time the patients received ineffective ventilation.

In 2011, Adelborg et al evaluated professional life-guard resuscitation performance, comparing mouth to mouth/pocket mask and BVM ventilation. Noting that amongst some lifeguards it was “common sense that BVM [was] superior” (despite the fact that it wasn’t a mandatory part of lifeguard training), their results demonstrate that this is probably a flawed assumption.

Finally, the Finns revealed ‘basic airway management’ for what it is, amongst a cohort of new/clinically inexperienced paramedics, who were allocated a cardiac arrest scenario utilising either BVM, LMA or ETI management after initial training – the group that achieved the poorest ventilation (and by inference airway control) were in the BVM arm! (Kurola et al 2004).

That’s OK, these days we don’t even bother with BVM …

The literature generally suggests LMA devices (v BVM) are easier to learn to use and are superior for airway control / ventilation with a number of people pretty much advocating canning the BVM and going straight for a LMA. Rechner et al (2007) showed that Critical Care Nurses with one hour of training on LMA insertion were able to maintain airway control and ventilate children 82% of the time using LMAs compared to 70% using BVM/adjuncts. Further, utilising LMAs (as opposed to BVM) in initial airway management of cardiac arrests appears to protect arrestees from gastric aspiration (Stone, Chantler, Baskett 1998).

However, while LMAs are undoubtedly the shizz and minimally experienced providers can generally insert them easily enough while supervised in the OT or during manikin simulation, success with this device does not appear to reliably carry over to the real life setting e.g. Hein et al 2008 with 65% success within 2 attempts during out of hospital cardiac arrest.

Now here’s a few useful acronyms I first came across at Life in the Fast Lane:

Difficult BVM = BONES

  • Beard
  • Obese
  • No teeth
  • Elderly
  • Sleep Apnea / Snoring

Difficult LMA = RODS

  • Restricted mouth opening
  • Obstruction
  • Distorted airway
  • Stiff lungs or c-spine

I was at a recent conference ‘show and tell’ type talk from a representative of a very high-performance paramedic based EMS system. Amongst other things, he talked about the level of audit and scrutiny applied to pre-hospital RSI performed by his service. At the end I asked if they audited the airway interventions/management of their non-RSI accredited providers (no). Realistically this group of providers will still be called upon to manage A and B, and when they do it’s likely to be because there is no backup available – I’m picturing a patient in some kind of extremis. Due to the clinical characteristics of this patient group (cardiac arrest, neurological emergencies, respiratory decompensation etc.), I’d imagine that if there was a negative outcome, it may be difficult to trace it back to a failure of some basic intervention in the kind of way you could if they were performing intubation +/- RSI.

In an methodologically dodgy study conducted by me (2016), non-physician providers (n=I can’t remember), were asked “if you were by yourself and had to bag someone, would you be confident that you could do it successfully?” The responses were generally polarised reflecting unflinching confidence in their abilities or cautionary pessimism that they would give it their best shot but were not optimistic – one told me “if they were honest with themselves most people would ”. This observation appears to mirror the findings of Kidner and Laurence (2006), who evaluated the basic airway and ventilation competence of junior doctors (n=20) on anaesthetized theatre patients. While pre assessment 85% said they were confident in their ability, only 40% demonstrated initial competence to the minimum standard.

Mr Tusko copy
I’d imagine some of my colleagues with smaller hands might be concerned about getting a good seal on Mr Tusko.

 

Where do you work?

There is a certain irony in our office at work. Over the way in aviation, our pilots are becoming more skilled and experienced almost every shift undertaking high risk, single pilot operations day and night. Yet they still have high volume training and re-currency requirements. Arguably, if they crash the plane we’re all screwed, but I’m not the first person to articulate the idea that we medical people have some lessons to learn from aviation. Raatiniemi et al (2013) have some suggestions about how to rectify the current state of affairs (from a setting that has practical similarities with EMS operations in rural and remote Oz):

– targeted airway management courses (not that such a thing actually exists!)

– simulation and manikin training

– supervised hands on time in OT (probably the gold standard)

– registering / auditing procedures to target training and supervision.

Care to Read More?

Here’s a good blog post on two v one person BVM and some other BVM stuff.

Flavel and Boyle’s excellent 2010 LMA vs BMV is worth a read (the full reference is below).

Additionally, Dr Aaron Conway’s research project “Survey to improve the quality of the training and education that nurses receive about conscious sedation” is worth pondering for the non-airway experts and I imagine the results of this study will provide an important contribution to this discussion. Check it out in detail here. 

Now the bibliography:

Adelborg, K., Dalgas,C.,  Lerkevang Grove, E., Jørgensen, C.,Husain Al-Mashhadi, R., Løfgren, B. (2011) Mouth-to-mouth ventilation is superior to mouth-to-pocket mask and bag-valve-mask ventilation during lifeguard CPR: A randomized study. Resuscitation 82, 618–622.

Flavel, E, Boyle, M. (2010) Which is more effective for ventilation in the prehospital setting during cardiopulmonary resuscitation, the laryngeal mask airway or the bag-valve-mask? – A review of the literature. Journal of Emergency Primary Health Care. 8(3)

Hein C, Owen H, Plummer J. (2008) A 12-month audit of laryngeal mask airway (LM) use in a South Australian ambulance service. Resuscitation;79:219–24.

 Kidner ,K. Laurence, A. (2006) Basic airway management by junior doctors: assessment and training on human apnoeic subjects in the anaesthetic room. Anaesthesia, 2006, 61, pages 739–742

Kurola, J. Harve, H. Kettunen, T., Laakso J.-P. Gorski, J. Paakkonen,H. Silfvast, T. (2004) Airway management in cardiac arrest—comparison of the laryngeal tube, tracheal intubation and bag-valve mask ventilation in emergency medical training Resuscitation 61 149–153

Noordergraaf, G, van Dun, PJ, Kramer, BP, Schors, MP, Hornman, HP, de Jong, W, Noordergraaf, A. (2004) Airway management by first responders when using a bag-valve device and two oxygen-driven resuscitators in 104 patients. European Journal of Anaesthesiology, 21(5)

Otten, D, Liao, M, Wolken, R, Douglas, I, Mishra, R, Kao, A, Barrett, W, Drasler, E, Byyny, R, Haukoos, J (2014) Comparison of Bag-Valve-Mask Hand-Sealing Techniques in a Simulated Model. Annals of Emergency Medicine, 63(1)

Raatiniemi L1, Länkimäki S, Martikainen M. (2013) Pre-hospital airway management by non-physicians in Northern Finland — a cross-sectional survey.. Acta Anaesthesiol Scand. May;57(5):654-9

Rechner JA, Loach VJ, Ali MT, Barber VS, Young JD, Mason DG. (2007) A comparison of laryngeal mask airway with  facemask and oropharyngeal airway for manual ventilation by critical care nurses in children. Anaesthesia. 62:79.

 Stone, BJ., Chantler, PJ, Baskett, PJF. (1998) The incidence of regurgitation during cardiopulmonary resuscitation: a comparison between the bag valve mask and laryngeal mask airway Resuscitation 38 3–6

Walsh K, Cummins F, Keogh J, Shorten G  (2000) Effectiveness of mask ventilation performed by hospital doctors in an Irish tertiary referral teaching hospital. Irish Medical Journal 93(2)

Wang, H., Mann, N., Mears, G., Jacobson, K., Yeal, D. (2011) Out-of-hospital airway management in the United States Resuscitation, 82 (2011) 378–385

Airway, Paediatrics, Uncategorized

Getting Things Straight

6 Comments

Lots of beliefs are hard to shake. Andrew Weatherall covers one from the paediatric airway – the holy status of the straight blade.

As I’ve mentioned before, paediatric airway management is full of mythological beasts. Some of that is about anatomy stuff and the like. Some is about equipment. Plenty is about technique. Sometimes it’s about technique and equipment together. Bliss.

So this is where I wade into another topic in paeds airways:

Straight blades are overrated and you should throw them away.

Marc Zimmer Dog Unicorn Dog
It is a time for mythical beasts. Like the fabled unicorn dog but less cool.

Do we need big bins?

Well, actually no. Stop the indignant letter writing. When I say they’re overrated I don’t mean they have no value. They have a role like most items of equipment that are still in use after nearly 100 years probably still have a role.

What I do mean is that straight blades are treated with a reverence in paediatric airway management that is unwarranted, while curved blades like the Macintosh seem to be described as “bigger people’s airway devices”. Trainees could easily go through their whole training period thinking that you must always use straight blades for patients who understand what the hell Pokemon are all about.

That just isn’t true. People who swear by straight blades will point to the more anterior epiglottis and the angle of the cords to argue the case for their chosen device just as convincingly as those who like a curved blade point out that they get more working space in the mouth and a familiar blade and both will be sort of right.

It might be useful to dive into this a little more. So let’s work through a paper from 2014 that specifically looked at the straight vs curved blade question. Partly because it gives an appropriate ‘meh’ when trying to split the two options but also because it highlights how myths can dominate our perception of the original work.

 

Welcoming the Contenders

The paper here appeared in Pediatric Anesthesia in 2014 (I touched on this in the other post). The authors set out with a useful question: is there a difference between Miller and Macintosh blades when it comes to ease of obtaining a view and success of intubation in the 1-24 month age range?

They looked at well kids having elective surgery under anaesthesia where muscle relaxation was also used. They included 120 kids and each kid had laryngoscopy with one device then the other.

The results are a case of a big old shrug, which is sort of OK. Easy laryngoscopy was noted in pretty much the same percentages. First pass success pretty much the same. The rates of one being better for the view than the other were pretty much the same. When it was difficult with one view the rate of switching to the other and finding it was easier was about the same regardless of whether you had started with the Macintosh or Miller.

So the two blades that stepped into the ring step out with no knock out punch thrown. There are a number of other interesting points when you look in more detail though and a few comments I’d make in passing.

  1. The epiglottis isn’t the endpoint

I have this impression that trainees get really obsessed needing to pick up and control the epiglottis with a straight blade. In this paper the routine use of the straight blade was to place the tip in the vallecula. In only 2 of the 60 uses of the Miller blade did they pick up the epiglottis.

Why do people get so antsy about picking up the epiglottis? It was only ever described as one of the options to obtain the view, not the only option. Those early designers never forgot the aim: to obtain a view to let you instrument the trachea.

Here’s Miller from the paper where he described his blade:

“The epiglottis is visualized and raised slightly to exposure the cords or, if the operator desires, the tip of the blade maybe placed in front of the epiglottis and raised sufficiently to visualize the cords after the method of Macintosh.”

In fact Macintosh described the straight blade being used in this manner when he reported on his own design, singling out Dr Margaret Hawksley as an exponent of this technique. The authors of this recent paper further point out that it’s a lot more stimulating to pick up the epiglottis. That’s worth at least a thought.

Miller wasn’t precious about how you get the view. The idea that picking up the epiglottis is the only technique just got repeated enough that no one remembers to question it. The epiglottis isn’t the main game. The view is the thing.

  1. Make sure of your basic technique

One of the other interesting features here is that there are some elements of the intubation technique that seem like they could do with a review. An example: the Miller blade was advanced centrally along the tongue. This is a technique taught by heaps of people and I think Miller probably would have strong feelings about that. Again let’s go back to the paper:

“The blade is inserted in the right side of the mouth, pushing the tongue to the left.”

One of the bigger challenges in getting a view in paediatric patients is getting the tongue out of the way. This is particularly for straight blades which tend to have less of a flange to do some of the work for you. I’m not the only one who thinks so, either:

“On passing the instrument into the mouth the tongue should be manipulated to the left side, away from the slot; otherwise the organ may roll into the barrel and completely obstruct the view.”

That was Magill. In 1930. Now Magill might have been describing the use of a speculum but the principle is the same. The tongue is only likely to make your view worse (and given that straight blades pose an additional challenge in having not as much space proximally to work in, that really matters).

Magill went on to point out that if you struggled at all you could move the proximal end of our instrument further to the right corner of the mouth – that’s also known as the paraglossal view and turns out to be pretty much the best way to go.

In other basic technique points the authors of this recent paper mention that laryngoscopy was done with the head in a neutral position. This doesn’t seem like optimal head positioning for use of either blade, and that’s another point worth keeping in mind.

  1. It’s useful to know what the intended use was with your instrument of choice

In this paper and in the comparison with the Cardiff blade they refer to as an example of other “blade vs blade” papers, a comment is made that when you introduce an endotracheal tube centrally you can compromise the view and that it’s not great for introducing your tube via any central channel.

Miller, again:

“The scope is used for visualizing the cords only. One should work outside the blade to insert the tube. The only criticism of the instrument has been that it is too small through which to work. It was not designed to be used as a guide for the catheter.” (That’s the author’s work with the italics, not an edit from me.)

In fact Miller searched for a new design because he felt small laryngoscope blades on the market were too big. It’s designed to be small.

So yes, you need to use a technique where you bring the tube in from the side. That was always the point.

  1. Should we stop talking about external laryngeal manipulation like it’s an extra?

This is really a bit of open musing on my part. This was done in over 50% of the patients in both groups and generally helped when it was used. I can see how the precision of description goes up when we include these details but it strikes me as so much a part of every intubation (as this external pressure means less work for the laryngoscope itself) that I wonder how much it adds to our appreciation of clinical use. That’s one for the comments section I guess.

Messages for the Prehospital or Retrieval Type

After sifting though all of that, what are the take home messages? Well, here are some from me that might need additions from others:

  1. Know what you do and why you do it

Those picking up a laryngoscope for the little people need to have thought through what they will use and why. If I’m offered a personal preference it is to use a curved blade for everyone. Even as a paeds anaesthetist I’ve just used a curved blade more. It’s better designed to control that pesky tongue. You get a huge working space within the mouth and with external laryngeal manipulation (which I’d call standard) you can pretty much always bring the airway into view, even in the slightly anterior larynx.

I haven’t seen a study that would confirm this hunch, but I wonder if one of the problems some prehospital clinicians have with paeds intubation is they pick up a laryngoscope they didn’t really learn, very rarely use or rehearse with and don’t really understand. You need to focus your technique slightly differently with a straight blade. Add the stress of the situation and is it any wonder the job becomes harder?

I’d back the occasional proceduralist as more likely to intuitively understand the anatomy using the same sort of blade they always use. I doubt it’s a study that would be easy to set up in anything but mannequins though.

  1. Know the different options

That preference for people using what they know doesn’t mean you shouldn’t learn both. This study did highlight that some kids just have a better view with a particular blade. You can’t quite get as good a view with one option, switch to the next and all of a sudden it’s easier. Again though if you’re reaching for that other option use it right.

  1. Make your technique appropriate for the 1% and the 99% will be fine

This is more of a general point. Laryngoscopy in infants is easy the vast majority of the time. So if you don’t bother controlling the tongue you’ll probably get by most times. It’s the 1% where your routine practice of not getting the tongue out of your view, or being able to aim for either the vallecula or epiglottis, or positioning the head right will start to bite.

If you always do everything to maximise your view, you’ve already got a good technique for the 1%. It’s best not to need to review your technique once the blade is in and you’ve figured out this is the tough one you’ve been dreading.

So after all that, maybe paediatric airway instrumentation comes down to a really simple refrain: the tool in the hand matters less than the tool holding it.

 

Notes:

That image comes from Marc Zimmer on flickr under Creative Commons and is unaltered.

Here’s the paper mentioned again:

Varghese E, Kundu R. Does the Miller blade truly provide a better laryngoscopic view and intubating conditions than the Macintosh blade in small children? Pediatric Anesthesia 2014;24:825-9. 

And the others …

A review on the popularity of the Macintosh blade:

Scott J, Baker PA. How did the Macintosh laryngoscope become so popular? Pediatric Anesthesia 2009; 19 (Suppl 1):24-9. 

Miller RA. A new laryngoscope for intubation of infants. Anaesthesiology 1946;7:205-6.

Macintosh RR. A new laryngoscope. Lancet 1943;1:205.

Magill IW. Technique in endotracheal anaesthesia. British Medical Journal 1930;2:817-20.

and the Cardiff paper:

Jones RM, Jones PL, Gildersleve CD, et al. The Cardiff paediatric laryngoscope blade: a comparison with the Miller size 1 and Macintosh size 2 laryngoscope blades. Anaesthesia, 2004;59:1016-9.

 

 

Airway, Paediatrics

Does video make for little airway stars?

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Most of us are always out for new techniques to make difficult cases easier. Videolaryngoscopy is one area of great change over the last decade. Here Andrew Weatherall looks at videolaryngoscopy as it relates to looking after the little kidlet airway. 

Seeing is believing. It can happen in a moment in sport. It’s the whole basis of magicians plying their trade.  Even people seeing mysterious circles appearing in crops want to believe.

Perhaps that impulse is why everyone wants to believe in videolaryngoscopy. And it makes sense. It’s persuasive. The view is better than your eyes alone. It must be better.

And yet … the evidence doesn’t help us back up our gut reaction. So the debate starts. It’s a pretty big debate too. Too big for here.

So let’s just talk about one bit. Let’s see where videolaryngoscopy fits in with kids.

Open Bias

I should declare an interest here. I like videolaryngoscopy. I work in operating theatres where it’s freely available. In our prehospital operation we use it as routine. This is not to say I don’t dig direct laryngoscopy. I just really like an intubating experience that’s a little more IMAX. That isn’t even because I’m particularly a gear junkie. I’m only interested in tech if it helps me do a better job looking after patients.

So what’s so great about videolaryngoscopy? It’s not the view that it gives. It’s the team that it gives. My subjective experience is that when taking on a  slightly challenging airway the greatest benefit of using videolaryngoscopy is that all members of the team managing the airway can appreciate what is going on.

Sharing the same vision is the quickest way to get everybody operating on the same page. It’s particularly beneficial in getting any airway assistant providing external laryngeal manipulation to line up the view in the best possible way.

These observations are the same ones that colleagues who are fans of videolaryngoscopy seem to make. They note some drawbacks too. (blood in the airway being the obvious one). More and more though, videolaryngoscopy is perceived as the go to option for the extra few % that makes intubation a sure thing.

So does the evidence match that perception? And if not, why not?

What’s the Problem?

Perhaps it’s worth remembering that difficult intubation in kids isn’t that common. Some of the morphological changes that might be associated with difficult intubation are relatively common on their own. Restrictions to neck extension, a small mouth and jaw, a big tongue and dysmorphic appearance may be associated with difficult intubation. Of course most with these features still have a straightforward intubation.

A team from Erlangen published a retrospective review not that long ago looking at this issue. Looking back over a period of 5 years (while excluding records that were incomplete or where intubation wasn’t relevant) they ended up looking at 8434 patients who had a total of 11219 procedures.  152 (1.35%) of direct laryngoscopies were classified as difficult laryngoscopies (grade III or IV views).

1.35% isn’t much. Note also that they are talking about laryngoscopy, not actual intubation or airway management. Certain surgery groups had a relatively higher rate (oromaxillofacial and cardiac surgery patients) as did kids under the age of 1. The wash-up is that if we were to choose videolaryngoscopy to help with difficult laryngoscopy, we’re choosing that for < 2% of the population. This choice is fine but we at least need to understand the size of the problem we’re trying to address.

The 2% is something like the size of one of the eggs vs that ginormous bug.
The 2% is something like the size of one of the eggs vs that ginormous bug.

The Numbers For VL

Well they’re in and they’re not particularly supportive of the idea that videolaryngoscopy in kids is vastly better. Here’s one study where Truview PCD and Glidescope didn’t help with the view and slowed things down. Here’s another small series where the Glidescope doesn’t necessarily help with the view.

Of course rather than keep picking out individual studies, we could try to take on board the evidence from a meta-analysis. Sun et al have done the hard work, looking at fourteen studies which had a randomised component to their study.

Their findings? Videolaryngoscopy generally improved the view of the airway in kids with normal airways or potentially difficult airways. However the time to intubation was longer in pretty much all groups. Interestingly, the rate of failure was much higher with videolaryngoscopy (there was lots of heterogeneity in the included studies so that particular finding probably needs more than a few grinds of the giant salt mill).

Cochrane has a review specifically in neonates which is useful … to demonstrate that there’s not enough useful evidence.

What Don’t the Studies Say?

Well it already looks like the answer is “much”. Perhaps this is what I take away from them.

1. The evidence doesn’t justify a move away from direct laryngoscopy

I think videolaryngoscopy is still best considered as a technique to use as an adjunct, building off really good direct laryngoscopy technique. If the spiel is that VL “improves your view by one Cormack and Lehane grade” then implicit in that is the assumption that your view was already optimised.

For the vast majority of patients who have a grade I/POGO 100 laryngoscopy, videolaryngoscopy can’t improve your view (obviously). However you may reach the same view with slightly more ease. This applies particularly to videolaryngoscopy options that build off a standard laryngoscope design (rather than the Glidescope for example which has its own special learning curve).

Wouldn’t logic say if you need to work less to achieve grade I, II or even III views, your technique runs the risk of becoming reliant on the extra % that videolaryngoscopy gives you? For video laryngoscopes that operate pretty much like standard laryngoscopes with a little bit extra, you need your technique with direct laryngoscopy to get you most of the way there. The “video” bit is for the last few percent.

So good training in direct laryngoscopy techniques remains vital.  Practitioners will still need to understand the difference in technique required for different laryngoscopes and what the implications are for patient positioning to optimise success rates.

2. More nuance in the research would be helpful

Meta-analysis relies on the contributing papers. There’s presently a bit of heterogeneity there, including in the level of experience in those using the devices. Follow-up studies (or just fresh studies) when people have become highly used to videolaryngoscopy would be an interesting addition to the literature – how long does proficiency take to develop?

What about managing the unanticipated difficult airway case? That seems to be a whole area that isn’t well addressed by the current literature. Or measurement of decision-making and overall management of the airway when videolaryngoscopy is available?

There’s also a tendency to focus on clumps of trees rather than the whole forest. This is pretty common to airway papers. Often the focus seems to be on ‘time to tracheal intubation’ (which isn’t the worst surrogate to choose) or, less productively, on the view of the glottis or first pass success. This touches on the same territory discussed by Alan Garner here on measuring surrogates rather than clinically meaningful parameters.

Seeing the glottis more doesn’t equate to the airway being managed.  First pass success isn’t the most vital of measures. Time to tracheal intubation from laryngoscope in hand might be a little more helpful, but is it more useful than time from induction to airway secure in the patient with a difficult airway? Should we be reporting on desaturation rates with one technique over another given that the aim of airway management isn’t just the bit of plastic?

3. Measuring teams

The other feature the literature doesn’t inform is that subjective sense of utilising the team better in difficult airway management. It would be really interesting to see some research that examined the impact of videolaryngoscopy on the ways teams worked together or communicated in the management of the airway. Or what about performance of teams managing the airway in out of theatre locations? As things stand the thing I subjectively feel is the best feature of videolaryngoscopy doesn’t seem to have been evaluated.

 

So where does that leave me? Not really anywhere different. Probably where it leaves me is in need of checking my own position on the seeing vs believing spectrum.

In the absence of evidence from other people I should probably rigorously examine my personal practice. Practice the use of different techniques until I feel proficient. Then measure my actual performance and see what my own benchmark performances are. Perhaps really rigorous personal auditing (not the Scientology version) is the next step in understanding how VL should fit into my practice and how it measures up to DL.

It’s only after that that I’ll really know if I’m seeing what I think I’m seeing.

 

The References:

Heinrich S, Birkholz T, Ihmsen H, Irouschek A, Ackermann A, Schmidt J. Incidence and predictors of difficult laryngoscopy in 11,219 pediatric anesthesia procedures. Pediatr Anesth. 2012;22:729-36.

Riveros R, Sung W, Sessler DI, Sanchez IP,  Mendoza ML, Mascha EJ, Niezgoda J. Comparison of the Truview PCD and the GlideScope video laryngoscopes with direct laryngoscopy in pediatric patients: a randomised trial. Can J Anesth 2013;60:450-7.

Lee JH, Park YH, Byon HJ, Han WK, Kim HS, Kim CS, Kim JT. A Comparative Trial of the GlideScope Video Laryngoscope to Direct Laryngoscope in Children with Difficult Direct Laryngoscopy and an Evaluation of the Effect of Blade Size. Anesth Analg 2013;117:176-81.

Sun Y, Lu Y, Huang Y, Jiang H. Pediatric video laryngoscope versus direct laryngoscope: a meta-analysis of randomized controlled trials. Pediatr Anesth. 2014;24:1056-65.

Lingappan K, Arnold JL, Shaw TL, Fernandes CJ, Pammi M. Videolaryngoscopy versus direct laryngoscopy for tracheal intubatio in neonates (Review) Cochrane Database of Systematic Reviews 2015. dii: 10.1002/14651858.

Over on Minh Le Cong’s site, he’s also previously shared something a little more positive on videolaryngoscopy.

The image here came from Flickr Creative Commons and is unaltered. It was posted by Alibi 0591.

Airway, Governance, Prehospital Trauma

Should we stop looking at first look intubation rates?

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A brief note: I get to do the editing duty this week (Dr Andrew Weatherall that is) and I could not let it pass without a word of tribute to Dr John Hinds. I had only had the chance to learn from the good Dr Hinds via his online presence. It was a big presence. 

As one who did not know him personally, I can only reflect that he demonstrated many of the best qualities of a passionate doctor and that his passing, far too soon, has revealed many of the best qualities of his colleagues. 

Just in case you needed another reminder, you could watch him in action here, or read good words by @Eleytherius here, or sign a really worthwhile petition to deliver a vision for a better prehospital service for patients in NI here. 

As to this week’s post, Dr Alan Garner has a post on looking for the right outcomes so we’re doing the right thing for our patients. 

Can’t see the wood for the damn trees

As part of their intubation quality program many services now report their first look intubation rate. We have been doing so for a couple of years now. This looks like a really good thing to do. We know that more than one attempt at intubation is associated with greater incidence of serious adverse events in critically ill patients, and the more attempts the more likely those adverse events become (reference 1).

Therefore a strategy of aiming for first look success is probably a good idea, a strategy that my own service employs. So this should be a good thing to report as a quality measure too. Indeed why would you not? After all, the more attempts, the worse things get right?

Well wait a minute …

First let’s have a think about why we would report it. Is it telling us something that actually matters?

The outcomes that really matter are did they die or end up with hypoxic brain injury. The process issues that really matter are did they get hypoxic or have a cardiac arrest during the intubation process. There are other hard complications/process issues you can measure too like aspiration with unnecessary additional ventilator days, or even did you break their teeth.

First look intubation tells us none of these things. It does not tell us if the patient became hypoxic, aspirated or even arrested. Yes it is associated with lower incidence of these complications but it does not tell you if the complication actually occurred.

And what if emphasising first look intubation rate as a quality measure shifts the focus in the wrong direction? Could you risk making the risk of hypoxia higher?

Am I losing the plot here? Let’s go back to first principles.

The outcomes that really matter are death and hypoxic injury. I don’t think anyone is going to argue these should be avoided. Fortunately the incidence of these is pretty low so we tend to use surrogates for these things instead, things like the incidence of hypoxia or hypotension/bradycardia during intubation. These are pretty direct measures reflecting outcomes that matter.

First look intubation isn’t an outcome. It’s not even a surrogate for an outcome – it’s a surrogate for a surrogate of an outcome. My concern is that surrogates for an outcome, rather than the actual outcome can lead you way up the garden path. The MAST suit again comes to mind. The patient’s BP went up so it had to be a good thing surely. Of course when someone finally did a decent study on the outcome that really mattered, mortality, it was trending to worse not better.

Although there are no randomised controlled trials showing hypoxia to be bad for you, the circumstantial evidence is pretty overwhelming so I agree this is not quite like the MAST suit situation. However in using first look intubation as a quality measure we are now reporting a surrogate for a surrogate of the outcome that actually matters. I.e. we are reporting first look as it is associated with lower rates of hypoxia because lower rates of hypoxia are associated with lower rates of death and brain injury.

This is a risky game and recent audits of my own service show why. For the past year we have had a monitor that records the vital signs every 10 seconds and we download the data at mission end and attach it to the record. I have been going through these records to see what our rates of peri-intubation hypoxia actually are.

First thing I need to say is that our first look intubation rate so far this year is 100%. However we did have a couple of episodes of significant hypoxia.

My concern is that by reporting the first look rate, we draw attention to it and we send the message to our teams that this is the thing that we think matters. So better to press on a little bit longer even though the sats are falling to make sure I nail that tube first time!

What was the big picture again? [via Jarod Carruthers on flickr under CC 2.0 and unaltered]
What was the big picture again? [via Jarod Carruthers on flickr under CC 2.0 and unaltered]
Why are we reporting a surrogate for a surrogate? I have really accurate data from the monitor on the peri-intubation hypoxia rate, hypotension, bradycardia and arrest. Why report a surrogate for these things that might actually encourage our staff to focus on the surrogate and cause an episode of hypoxia, bradycardia, hypotension etc.

It remains important to emphasise optimising conditions for the first intubation attempt as that appears to have lower complication rates. However it is a means to an end. We should emphasise the outcomes (or at least the surrogates with only one degree of separation from that outcome) that matter. Why report a surrogate for a variable when you have the data to report the actual variable?

Some services like our own are now reporting 100% first look intubation rates, but no one is yet reporting 0% peri-intubation hypoxia rates. Aim for first look intubation as that appears to be a smart strategy, but tell your people it is the hypoxia that matters by making that the centre of attention in your reporting.

What do we mean by hypoxic?

Another thing I have been forced to look at is the definition of peri-intubation hypoxia. I had intended to use the definition of hypoxia used in many of the studies on this subject:

“Desaturation was defined as either a decrease in SpO2 to below 90% during the procedure or within the first 3 minutes after the procedure, or as a decrease of more than 10% if the original SpO2 was less than 90%.” (reference 2, see also 3-5)

I excitedly opened the data file of our first patient that we had intubated when we got our shiny new monitor a year ago to see what had happened. It was easy to identify the timing of intubation from the capnography data as we routinely pre-oxygenate our patients with a BVM device with the capnography attached. The sats pre-induction were a steady 90%, for 2 readings they were 89% (20 seconds) and then climbed to 98% when ventilation was commenced. So according to this definition we had a desaturation!

I don’t think anyone would claim a fall in SpO2 of 1% is clinically significant. It is also less than the error of the measurement quoted by the manufacturer of the oximetry system. This set of circumstances is not going to occur that often but it does not make sense to classify this case as a desaturation. We have therefore modified our definition to:

“Desaturation is defined as either a decrease in SpO2 to below 90% (minimum change at least 3%) during the procedure or within the first 3 minutes after the procedure, or as a decrease of more than 10% from the pre-intubation baseline if the original SpO2 was less than 90%.”

So what should we be reporting?

Thomas reported that each subsequent attempt at intubation was associated with an increased risk of hypoxia, aspiration, bradycardia, cardiac arrest etc. If we have the data on these variables then why not report them directly instead of reporting the surrogate for them. For hypoxia I would suggest our slightly modified definition above.

As for other variables why not use the definitions from Thomas’ paper?

Bradycardia HR <40 if >20% decrease from baseline
Tachycardia HR >100 if >20% increase from baseline
Hypotension SBP <90 mm Hg (MAP <60 mm Hg) if >20% decrease from baseline
Hypertension SBP >160 if >20% increase from baseline
Regurgitation Gastric contents which required suction removal during laryngoscopy in a previously clear airway
Aspiration Visualization of newly regurgitated gastric contents below glottis or suction removal of contents via the ETT
Cardiac arrest Asystole, bradycardia, or dysrhythmia w/non-measurable MAP & CPR during or after w/in intubation (5 min)

 

For the physiological definitions Thomas includes percentage change from baseline like we do with the hypoxia definition. This acknowledges that these are critically ill patients and often have deranged physiology before we start. These definitions can therefore be used in the real world in which we operate. If we all adopted these definitions we could meaningfully compare ourselves with Thomas’ original paper and with each other.

And as for us…

We are seriously thinking about ditching the reporting of first look intubation rate. It is not telling us what really matters – and we can’t get better than our current 100% rate anyway. Despite this we are having occasional episodes of hypoxia and other complications, and it is possible that the rate of these complications are being exacerbated by emphasising first look.

We are therefore looking at moving to the much more comprehensive set of indicators used by Thomas (along with our modified hypoxia definition). This will demonstrate to our team members the factors that we think really matter, because we measure them and report them externally.

You could argue that the only way to achieve 0% hypoxia is to accept that we are not going to have a 100% first look intubation rate. I for one would gladly give up our 100% first look rate if in doing so we achieved 0% hypoxia. I don’t yet know if this is achievable but I have some ideas. Those who walk the quality & patient safety road with me know that we might never arrive, but that should not deter us from the journey.

Anyone coming?

 

Reference:

1 . Thomas CM.   Emergency Tracheal Intubation: Complications Associated with Repeated Laryngoscopic Attempts. Anesth Analg 2004;99:607–13. [Full text.]

  1. Anders Rostrup Nakstad MD, Hans-Julius Heimdal MD, Terje Strand MD, Mårten Sandberg MD, PhD.   Incidence of desaturation during prehospital rapid sequence intubation in a physician-based helicopter emergency service. American Journal of Emergency Medicine (2011) 29, 639–644

 

  1. Reid C, Chan L, Tweeddale M. The who, where, and what of rapid sequence intubation: prospective observational study of emergency RSI outside the operating theatre. Emerg Med J 2004;21:296-301.

 

  1. Omert L, Yeaney W, Mizikowski S, et al. Role of the emergency medicine physician in airway management of the trauma patient. J Trauma 2001;51:1065-8.

 

  1. Dunford JV, Davis DP, Ochs M, et al. Incidence of transient hypoxia and pulse rate reactivity during paramedic rapid sequence intubation. Ann Emerg Med 2003;42:721-8.
Paediatrics

Revisiting Old Stories About Little Airways

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Dr Andrew Weatherall returns to stuff about paediatric airways, a bit of a companion to an earlier post with some practical tips. 

There are some things you’re taught from a very young age to believe in. Then it turns out it’s just plain wrong. Santa Claus. The Tooth Fairy. The Public Holiday Numbat. (Well, the last one might be specific to my upbringing.)

And in medicine there are plenty of examples those too. Oxygen is always good. You can’t manage trauma without a cervical collar. Then of course there’s pretty much everything about the paediatric airway. As if managing kids didn’t come with challenges anyway, we all get to work with information that is just plain wrong.

And there’s no mistaking that clinicians find paediatric airways difficult. The staff from Royal Children’s Hospital Melbourne have recently published a sizeable prospective study of emergency department intubations. This is from a big, clinically excellent tertiary kids’ hospital receiving 82000 patients in their ED every year. In 71 intubations across a year (only 71!), 39% had adverse events (most commonly hypotension in 21% and desaturation in 14%) and the first pass success rate was 78% (only 49% had a first pass intubation with no complications).

Now lots of things will contribute to those figures. But at least part of pondering that has to be making sure we understand what we’re dealing with.

"Please, go on" says Public Holiday Numbat [unchanged via quollism on flickr under CC]
“Please, go on” says Public Holiday Numbat [unchanged via quollism on flickr under CC]

Old Truths

Some old historical truths are harder to pull away than a spider web stuck to a bear with superglue. There’s a recent review that appeared in Pediatric Anesthesia written by Dr J Tobias  which steps through some of this dogma.

It points out that some of the classic teaching on the paediatric airway come out of a 1951 report by a Dr Eckenhoff. This includes the issues of the position of the larynx, the shape of the epiglottis and the funnel-shaped airway. Actually, to really trace the story, you have to start a little earlier.

Stepping Back

It’s 1897. Waistcoats aren’t ironic yet. Pipes aren’t an affectation they’re an expectation. Jack the Ripper is part of shared memory, not fevered historical narratives. And Bayeux was making casts of the airways of dead children. 15 casts actually in kids aged 4 months to 14 years.

Taking measurements of the circumference of the airway at the glottis, cricoid level and trachea, the cricoid ring was noted to be narrower than other parts of the airway (the topic of the shape of the airway wasn’t mentioned). This is the work that led to the idea that kids under the age of 8 had a conical larynx, with the cricoid ring as the narrowest point.

Consider for a second the qualities of plaster poured into a distensible tube. Wait, it’s not entirely distensible because the cricoid can’t distend. Is it maybe possible that the plaster may have distorted the anatomy? I’ll leave that with you for a bit.

This suggestion of the conical airway made its way into Eckenhoff’s later paper (though with a specific note that cadavers may not represent the living accurately). There were also some descriptive points raised:

  • The larynx moves down from the C3-4 level in the neonate to C4-5 in the adult (I’ve always been under the impression this move is brought about both by the need to phonate properly for speech and the loss of the need to breathe and breastfeed at the same time, but this point doesn’t feature in airway descriptions and I’m happy to be corrected).
  • A stiffer and more “U” or “V”-shaped epiglottis with an angle to the anterior pharyngeal wall of around 45 0 rather than lying close to the base of the tongue.
  • A case report of a 2 year old with airway complications thought to be related to an inappropriately sized tube, feeding the idea of uncuffed endotracheal tubes in kids under the age of 8.

All these points that form part of so much teaching lead to another question – would such a descriptive effort get a run in modern publishing?

 

Newer Tools Means Better Understanding

The answer of course is probably not. Of course you can only use what you have and it’s absurd to judge Eckenhoff (or Bayeux) for their accuracy against modern modalities. All we can do is revisit our thinking when new information becomes available.

We now have the significant advantage of radiological techniques (CT or MRI) and bronchoscopy to evaluate airways in children who aren’t dead. Again the Tobias article goes into more details but there are some key things to take from this modern literature:

  • In spontaneously breathing and muscle relaxed patients, the cricoid was not the narrowest part of the airway. That honour belongs to the vocal cords.
  • There is no change in the ratios of the cross sections over age – the cricoid doesn’t start relatively smaller and enlarge by the time you hit 8.
  • The cross-section looks like an ellipse (there’s more distance between the anterior and posterior bits than the two side bits).

 What should we do then?

Well for starters we should probably settle the tube choice thing. This is just more support for the argument to use a cuffed tube. For starters, the old “leak” test seems pretty dubious when you could be snug against the lateral walls but still leaking around the anterior or posterior areas. And I’m guessing no one has had their “leak accuracy assessment” externally audited.

It makes more sense to use an appropriately sized cuffed tube with the cuff pressure kept < 20 cm H2O. There’s now fairly convincing evidence that appropriately used cuffed tubes don’t cause big issues in recovery. Better ventilation, better monitoring, less flows and gentler tube material in contact with the mucosal wall. Makes sense.

What you can’t do is ignore the cricoid. It is still an unyielding bit of the anatomy and anyone can turn a high volume-low pressure cuff into a high volume-high pressure cuff – the difference is a couple of mL. And swelling in an airway that starts with a much smaller cross-sectional airway still means less margin for flow obstruction.

So choose the right tube, use it safely and you can get on with things.

 

While We’re At It, Let’s Forget One Blade to Rule Them All

Seeing as we’re talking about things that aren’t things, you may have also come across the idea that you should use a straight blade for the smaller kids (say, kids under 2). I’ve mentioned elsewhere that I think this is baloney but here’s a little bit of evidence.

Varghese and Kundu have published something on exactly this issue. 120 kids aged from 1-24 months had laryngoscopy (once anaesthetised and given muscle relaxation) with either a Miller or Macintosh blade, and then crossed over to the other type of blade. (Note they used both with the tip in the vallecula.)

The findings? The views were pretty much the same. The rates of difficulty were about the same. In fact, it’s a pretty beige set of numbers where being beige is actually as cool as things could be.

Some where the view wasn’t so great with a Macintosh had a better view with the Miller blade. Some went in reverse. The message though is a pretty resounding “same, same”.

 

So there’s just some truths that needed revisiting. There are no funnel-shaped airways. The airway isn’t round. There’s not one correct blade for the under 2s.

I still resent having to give up on the Public Holiday Numbat though.

References:

Here are the PubMed links for those mentioned in this post.

Long E, Sabato S, Babl FE. Endotracheal intubation in the pediatric emergency department. Pediatric Anesthesia 2014;24:1204-11. doi: 10.1111/pan.12490

Tobias JD. Pediatric airway anatomy may not be what we thought: implications for clinical practice and the use of cuffed endotracheal tubes. Pediatric Anesthesia 2015;25:9-19. doi: 10.1111/pan.12528

Varghese E and Kundu R. Does the Miller blade truly provide a better laryngoscopic view and intubating conditions than the Macintosh blade in small children? Pediatric Anesthesia 2014;24:825-9. doi: 10.1111/pan.12394

Prehospital Trauma

A Short Video About Bleeding Airways

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Managing the airway in prehospital and retrieval medicine is a challenge and has inspired many a discussion in many a setting. And anyone working in the area would appreciate the additional challenge when there’s lots of blood getting in the way.  As a result everyone has tips and and tricks to try and manage things.

This is by no means the first time people have come up with an approach (or shared an approach) but in the spirit of wide-ranging discussion, here’s a suggestion from Dr Alan Garner recorded for posterity in video.

It runs for about 10 minutes and you’ll note that at the end there’s an update as the approach evolved.

All thoughts, feedback and experience very welcome.