Ep. 20 - Out of Hospital Airway Adjuncts: King Tube vs LMA

King Tube vs IGEL for Airway Management

In this episode of Wilderness Medicine Updates, Dr. Patrick Fink addresses a listener's question on whether to use a King Tube or an IGEL as an out-of-hospital airway adjunct. The episode begins with an overview of airway management techniques from mouth-to-mouth resuscitation to supraglottic airway devices. Dr. Fink explains the benefits and drawbacks of various airway adjuncts, including oral and nasal pharyngeal airways. The discussion then shifts to a detailed comparative analysis of King Tubes and IGELs based on retrospective and prospective studies. Dr. Fink evaluates the evidence indicating that IGEL may be more effective and easier to use than King Tubes, particularly in pre-hospital cardiac arrest situations. The episode concludes with recommendations for pre-hospital providers and an encouragement for listeners to share their questions and feedback.

Links:

iGel LMA

King Tube

Smida T, Menegazzi J, Scheidler J, et al. A retrospective comparison of the King Laryngeal Tube and iGel supraglottic airway devices: A study for the CARES surveillance group. Resuscitation. 2023;188:109812. doi:10.1016/j.resuscitation.2023.109812

Smida, Tanner & Menegazzi, James & Crowe, Remle & Scheidler, James & Salcido, David & Bardes, James. (2023). A Retrospective Nationwide Comparison of the iGel and King Laryngeal Tube Supraglottic Airways for Out-of-Hospital Cardiac Arrest Resuscitation. Prehospital emergency care. 28. 1-13. 10.1080/10903127.2023.2169422. 

Lønvik, M.P., Elden, O.E., Lunde, M.J. et al. A prospective observational study comparing two supraglottic airway devices in out-of-hospital cardiac arrest. BMC Emerg Med 21, 51 (2021). https://doi.org/10.1186/s12873-021-00444-0

Chapters

00:00 Introduction and Listener Question

00:55 Understanding Airway Adjuncts

02:12 Basic Airway Management Techniques

06:34 Advanced Airway Devices: King Tube and LMA

11:35 Comparative Studies on Airway Devices

17:35 Prospective Data and Final Thoughts

25:24 Conclusion and Listener Engagement

As always, thanks for listening to Wilderness Medicine Updates, hosted by Patrick Fink MD FAWM.

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Transcript

Patrick: 0:07

hello and welcome back to Wilderness Medicine Updates the show for providers at the edges. I'm your host, Dr. Patrick Fink, and today we're gonna talk about out of hospital airway adjuncts. This comes from a listener question. I want to say thank you to Tom Huck, who wrote in with this question from the Black Forest Mountain region in Germany. With a question about whether the team that he volunteers with should be focusing on using the King tube. We'll talk more about what that is shortly, or the LMA and whether there's any evidence to support the use of one or the other. And thankfully, there are some good studies to guide our thinking on this. So let's jump right in. To begin with, let's do a little introduction where we talk about what I mean when I say an airway adjunct. So I'll march you through how I think about providing respirations in the pre-hospital environment. I see there exists a spectrum, and this spectrum spans from mouth to mouth resuscitation, yuck, all the way up to anything which involves the use of an endotracheal tube. So that is intubation, cricothyroid, otomy, where there is what we would call a definitive airway or a tube inside the larynx, a hundred percent. If we put air in that tube, it's going in and out of the lungs. So at the lower end of the spectrum is the potential for providing mouth to mouth respirations to someone who has insufficient or absent breathing. To my mind, this is completely off limits within the professional context because it is an unacceptable level of exposure to body fluids. There's just no body fluid, body substance, isolation happening there. This is something I would do for. A close friend or family member, but in the professional context, I would never do it. And the second reason I would never do it is because I'm always prepared to avoid this situation. So that brings us to the true bottom floor of pre-hospital airway management, which is the use of a ventilating mask. This is a CPR type mask. It's roughly the shape of a cupped palm. You can place it over the mouth and nose. And anyone that is worth its salt has about a, I would say centimeter and a half diameter tube, which leads in and out and has a one-way valve on that. That lets us breathe air into a patient. It lets exhalation go out a different way, and thus, if the patient were to vomit while we are providing respirations, that vomit does not go into our mouths. Yuck. But this is pretty inconvenient to use just this mask because we're having to bend all the way down right up next to the patient's mouth if we're trying to provide other interventions. At the same time, it's just challenging to manage. So this might be what I carry in my pocket when I'm skiing around working as a ski patroller, or what I carry in my backpack when I'm ski touring. But if I'm thinking about any degree of prolonged care or resuscitation, the next thing that I'm gonna add to that is a bag valve mask. So the mask for a bag, valve mask is the same as a CPR mask, but we add to that a bag. It's roughly the size of an American football, a rugby ball. It's soft. When we hook that up to our mask and we squeeze it, it provides ventilation, it squeezes that air into the lungs. It gives us some additional benefits. It can come with some bells and whistles. The main benefit is that you can squeeze it with one hand. You can be doing other things provided that that mask is secured to the face by someone else. The other benefit is that it can have a pressure meter on it, so you ensure that you are not squeezing too hard, and it may also have a peep valve or a positive and expiratory pressure valve. Basically, this says how much force can come back out, and this can help us keep the lungs inflated in between breaths. So I love a peep valve, particularly on people who are overweight, have a lot of chest wall. Pressure or tissue, um, or maybe resistant lungs if we're treating someone who has asthma and we need to help stent those airways open. That peep valve is a simple screw down device that lets me choose to give five, maybe 10 rare cases, maybe 15 millimeters, mercury of expiratory pressure. So that's the standard bag valve mask, and it's ubiquitous on ambulances and in rescue kits and throughout hospitals, everywhere. The next layer that I would add to that are where we really get into, we would call an adjunct or like an add-on, and those are the oral pharyngeal airways and the nasal pharyngeal airways. Oral pharyngeal airway is basically a fancy curved popsicle stick, which you can slide into the mouth. It helps hold the tongue forward so it's not sliding backwards and obstructing respirations. It makes it easier to bag that patient with the bag valve mask the nasal pharyngeal airway. Is essentially just a latex rubber tube which slides into the nose and gives us the same benefit that it stents open the air and allows air to travel into the posterior oropharynx without the resistance of those tissues. These are great tools because someone who is unconscious is all relaxed and is trying to snore, collapse their airway. Make it as hard as possible for you as the rescuer to provide effective ventilations. So we can add an oropharyngeal airway, a nasopharyngeal airway, into our unconscious unresponsive patient used with the bag valve mask. It's now easier to ventilate that patient. But what if that is insufficient? Either we're having trouble making air go in and out using those tools, or there's something else that makes us worried about the patient's airway. A couple different reasons that that could happen. This is not a comprehensive list, but say the patient is vomiting and we're worried about vomitus going from the esophagus down into the lungs. Bad situation, aspiration doesn't work well with ventilation, or perhaps this patient is going to be subjected to a prolonged transport, and then we want to have something a little bit more secure that is harder to dislodge and we don't have to be constantly reapplying that mask to the face every time we want to give a ventilation. So the next step up from a bag valve mask with adjunct like oass and NPAs becomes what I would call a supraglottic device. And that blanket category includes laryngeal mask, airways, everything from an intubating LMA to an IGEL. It might include a combi tube or a king tube. And these are essentially tools which. Try to direct the ventilation from the bag valve mask more directly through the vocal cords into the trachea. They are not what we would consider a long-term definitive airway because they don't actually enter into the airway. There's no a hundred percent guarantee that the air that you put in there is gonna go into the lungs. But they do a much better job than a simple bag valve mask at protecting against things like aspiration from vomitous and people who are difficult to ventilate with. The bag valve mask alone can be much easier to manage with one of these devices in place. The two devices that we're gonna talk about today are the king tube. And the LMA, so I'll break those two down. To start with, the king tube is essentially a long plastic tube, which has two balloons on it, one at the end, and one a few inches up from the end. This tube is inserted blindly into the esophagus and you inflate both of the balloons. And the idea is that then the balloons are above and below the laryngeal opening. Between those balloons is where the air port is, so that if you push air in and out of the king tube or the combi tube, that air is going to be delivered to the area around the vocal cords, and the balloons above and below will exclude contents from the trachea and will also seal off the outside world so that your pressure can be delivered directly to the trachea. These were really popular for a long time. It's relatively easy to insert blindly a tube into the esophagus. That's where tubes go if you just shove them into the mouth, but their efficacy is at best. Okay? They did a perfectly reasonable job for quite a while until along came a second device called a laryngeal mask airway. Take a look in the show notes for pictures of both of these devices, both the king tube and the LMA. But the way that I think of an LMA is it's going to take the shape of that CPR mask. That bag valve mask, the part that actually interfaces with the face, which I think of as being the shape of a cupped palm. And it shrinks it down enough that we can slide it past the tongue and let that cupped palm sit directly over the laryngeal opening. And there's a few different versions of this. Some of them are inflatable so that you can put a deflated one down into the, posterior oropharynx, and then you inflate it to put pressure up against that opening and create a seal. Others are very cleverly designed like the igel, such that the shape simply sits very nicely over the laryngeal opening. These. By kind of creating a seal over the airway opening, perform the same function of excluding any contents which happen to rise from the esophagus as vomitus. And they also help seal against the outside world so that any ventilations we provide are going in and out of the lungs. The LMA is a little bit of a newer device. The king or combi tube is a little bit older. So now let's jump into Tom's question. So Tom works as a volunteer on a rescue group, and he said that until recently our guidelines stated that a king LT tube should be our preferred airway adjunct for CPR, and that after some initial bag valve mask ventilation, we should switch to that king LT tube as fast as possible. But there were some concerns that King LT tubes can be misplaced, particularly by less experienced volunteers. And the newer guidelines suggest that an IGEL laryngeal mask airway should be the preferred device. The notion there. According to Tom was that the IGEL should be better for less experienced medics, but that's struck him as odd because the mechanics of inserting a king LT tube seem pretty foolproof. And with the IGEL, he questioned whether there could potentially be improper sealing around the larynx. And these are, you know, providers who are at the equivalent level of an EMT basic. So his question was whether there's any evidence out there that would support the use of either an LMA type device or a king LT for use in pre-hospital cardiac arrest situations. The first study that I want to talk about is called a retrospective comparison of the King laryngeal tube and IGEL Supraglottic Airway Devices, a study for the CARES Surveillance Group, and this is by Smita Etal in Resuscitation 2023. This was a retrospective study that analyzed data from the cardiac arrest registry to enhance survival, the CARES Registry, and it compared outcomes in out of hospital cardiac arrest between patients managed with either the king laryngeal tube or the IGEL supraglottic airway device. It included only nontraumatic out of hospital cardiac arrest cases with attempted EMS resuscitation, and this spanned 2013 to 2021, which is roughly when the LMA kind of came into being. I would say probably in 2013, king tube and combi tube devices were more common. And by 2021, a lot of hospital use had switched over to the LMA type device. Now they used a multi-variable logistic regression in this registry to attempt to account for other variables such as age, sex, initial EK, G rhythm, whether or not cardiac arrest was witnessed, et cetera, to try to reduce the comparison to just the airway device used. Now, the primary outcome that they measured was survival with a favorable neurological status. So. You know, awake able to perform activities of daily living, et cetera. And their secondary outcome included survival to hospital admission and survival to hospital discharge. So what did they find? The results showed that use of the I-G-E-L-L-M-A was associated with a 45% increase in the odds of a favorable neurological survival. So their odds ratio was 1.49, um, with a confidence interval, not spanning one for the stats nerds out there. Uh, a solid effect. Additionally, IGEL use was linked to a 7% increase in survival to hospital admission with an odds ratio of 1.07 and a 35% increase in survival to hospital discharge. So these findings suggest that the IGEL may be more effective than the king LT in helping to improve survival and neurological outcomes in out of hospital cardiac arrest patients. The second study that I'd like to bring your attention to is a similar study using a different registry called a retrospective nationwide comparison of the IGEL and king laryngeal tube Supraglottic airways for out of hospital cardiac arrest resuscitation, and this is in pre-hospital emergency care, January of 2023. In this study, it was a retrospective study using a. Different registry from the ESO Data collaborative over the years 2018 to 2021, comparing outcomes of, out of hospital cardiac arrest in patients managed with the IGEL or the KL NAL tube. Again, it was isolated only to non-traumatic out of hospital cardiac arrest cases where EMS attempted to resuscitate the patient and they put in a device. Their primary outcome was survival to discharge home and secondary outcomes include first pass airway success. So did they succeed in putting it in the first time return of spontaneous circulation? Did they get a pulse back and did the patient re-arrest in the pre-hospital environment if they did get a pulse back? So they use the same kind of mixed effects logistic regression to try to isolate the comparison to just the airway device used kind of. Using statistical wizardry to take age, um, you know, medical comorbidities, other, other such things out of, out of there. So this looked at 9,456 patients of whom 59.8% were treated with the IGEL, the remainder with the king tube. What did they find? Use of the IGEL in this registry as well was associated with a greater survival to discharge home with an odds ratio of 1.36 and higher first-pass airway success and odds ratio of 1.94 and increased return of spontaneous circulation of 1.19 compared to the king lt. It was also linked to lower odds of pre-hospital re-arrest at an odds ratio of 0.73 in this registry. However, when it was used as the primary airway management device, they did find that the IGEL was not associated with significantly greater survival to discharge home. They showed an odds ratio there of 1.26 with confidence intervals from 0.95 to 1.68. So there is actually a signal that probably it may help with survival to discharge home, but it didn't reach significance in this still relatively large sample. So there's some discord there between the study and the prior. However, survival, neurologically intact survival, these kinda match between the two studies. So between the two, the findings suggests that overall the IGEL may be more effective than the king LT in improving some outcomes in out of hospital cardiac arrest patients. Now, both of these studies suffer from the same shortcoming, which is that it is a retrospective study. So we don't know a lot about why. For example, an IGEL or a King Tube might have been used. My guess is that it's predominantly based on the transporting agency, but it's possible that we are blind to some patient characteristics that made. You know, the EMTs put IGEL LS in people who they thought were gonna do better, and kings in people they thought were gonna do worse. And that the differences that we've seen between these two groups are due to unaccounted for variables. And that's the problem with retrospective studies in general. So what about prospective data? Well, the last study that I'm gonna draw your attention to is called. A prospective observational study comparing two supraglottic airway devices in out of hospital cardiac arrest. And this is an open access article. Um, by, I apologize, I'm gonna butcher this. Lone Vic etal. And this is in BMC Emergency Medicine from 2021. So in this study, this was a prospective forward-looking observational study of the IGEL versus the king LTSD device, a slightly different king tube. And it compared two EMS services that were protocol to use the IGEL to one that was protocol to using the king tube. They included 250 patients. Who had an out of hospital cardiac arrest, and they aim to evaluate the difficulty of insertion, the number of attempts required for successful placement and the overall success rates of the devices. The findings of this study indicated that both devices had pretty high success rates with. First attempt insertion of the IGEL in 92% versus the UM, king device in 89%. The medium time to insertion was similar for both devices, but overall fewer attempts were required for the IGEL. Um, then for the King Airway Supreme. So this suggests this, uh, possibly a slight benefit to using the IGEL over this King device. However, with no significant difference in complications between the two and relatively similar rates, it seems like I. At least prospectively, at least they are similarly easy to use. The main limitation of this study is that they didn't look at very many patient-centered outcomes, and there's not really any record of the training or experience of the services using these or other devices prior to the study. So if one of these was new to them, it could have been more challenging to insert. So those are the three main studies that I was able to dig up giving us insight into I-G-E-L-L-M-A versus King. Here's my take on it. The data isn't perfect. I'm surprised that there isn't a prospective head-to-head randomized controlled trial that I could find, but we've got what we've got. It looks like in retrospective out of hospital cardiac arrest registries, the IGEL seems to beat the king by a fair margin to produce neurologically intact survival. So I think we can safely interpret that to mean that it's a generally superior device for providing oxygenation and ventilation during out of hospital cardiac arrest. Now, as I mentioned before, it's possible that the results are confounded. Meaning that there are variables that we can't account for and maybe higher performing groups are using the IGEL, while volunteers are all using King Airways, and that could entirely account for the observed difference. But the third study that we discussed in Norway with, you know, different EMS groups suggest that probably that difference doesn't account for all the effect. I think that generally people who think that the King Airway device is superior. To the IGEL have a preference for the King airway device due to familiarity, these were standard issue to a large number of EMS services for quite a long time. There is a study out there of novice users using both the king and the IGEL in a simulated tactical environment, which we didn't discuss here. And novices generally prefer the IGEL airways and found them easier to use. So if you like the king airway and you think it's easier to use, you probably like it because you're familiar with it. My experience in the emergency department receiving patients from the field with Supraglottic Airways in place is that, generally speaking, the IGEL doesn't lie. If you put in an IGEL airway, if it looks like it's in, it's in and the air is probably going where you want it to go. On the other hand, the king can lie because it can ride a little high, it can ride a little low, and if one of those two balloons happens to be sitting over the larynx, then the air is not going where you want it to go. So the simplicity of the IGEL I favor, if you've slide it in past the tongue, if you can't push it further, it's essentially in place. If you encounter a problem of air leak, meaning you're trying to put in air and you hear it coming out from around the device, you try to push it in a little further and seat it nicely, and if that doesn't do it right, then you're probably off by a size. You either need to upsize or you need to downsize. And anyone who is familiar with the use of the IGEL knows that probably 95% of adult patients can be successfully treated using a size for I-G-E-L-L-M-A, which is the green one. But in some big people, we gotta go up to the orange one, or you might have to go down a size if they're smaller. So it's not a panacea to use size four, but it works a heck of a lot of the time. And it's not as germane to this discussion of pre-hospital treatment, but also when the patients get to the hospital, it's a lot easier to manage them with that IGEL in place. Why? The answer is I can secure their airway through the IGEL using a fiber optic scope. It's built for that. We can keep breathing for them. While I do that, I can put a scope through it and slide an endotracheal tube in there. No problem. If there's a king tube in there, unfortunately I have to pull it out before we start to intubate. In most cases, it's not an issue, but in some tenuous airways, it's pretty nice to be able to ventilate while securing the airway or be able to fall back on the IGEL if need be. Definitely the most common issues with the IGEL is running in, or any laryngeal airway for that matter, is an air leak. And as I discussed, the easiest way to treat this is usually just to advance it slightly and make sure it stays secured, and then if not to change the size. The other pro tip that I have for you for the pre-hospital environment is that. Using an extension set, basically a little crinkle tube that allows you to attach your BVM to the LMA with a bend or a little bit of extension. Really helps when transporting in the pre-hospital environment because you have to occasionally put the bag down, lift the patient, move the patient. And when you do that, a little extension set keeps that bag from pulling on the airway and potentially displacing it. So if you're buying the IGEL for your agency, there are two packaging types and one of them comes with that flexible linking hose and a securing tie. And the cheaper one comes with just the IGEL alone. I like the first one. I like the full package because it really reduces jostling the airway and makes it easier to bag the patient when in a chaotic environment. So that's it. That's what I've got on King versus IGEL. My personal bias is that I trained with the IGEL and my contact with the King Tube has been through more rural EMS agencies that are still using these until they probably expire and then have an opportunity to purchase new airway equipment. But if you haven't had the chance to use an I-G-E-L-L-M-A, you should train on it. You can reuse one of them indefinitely for training, and they're super easy to use. I carry one in my ski patrol vest. I carry a size four LMA because in some situations you really can't beat it. Thanks again for listening to Wilderness Medicine updates. I hope that this has been useful to you. As always, I encourage you to write in with questions. I really appreciate hearing from listeners from around the globe Recently, there's been a lot of outreach from both Germany and South Africa, which is awesome, but I know that there's a bunch of you out there in other countries as well, and the uk, Europe, Australia, New Zealand, the United States and Canada. So if I haven't heard from you, I'd love to. If this raises any questions or you have any issues that you're running into with your team, please send those questions my way because if you have questions, someone else does and we can really try to get an answer dialed. Until then, if you find this podcast useful, as I've mentioned before, there's two ways that you can support me. The first is on whatever platform you're using, whether it's iTunes, Spotify, or something else. Give me that five star rating that helps us get exposure to more people out there. Get suggested by the algorithm. And then the other thing you can do for me, which is super helpful, is if you have another EMT doctor, nurse SAR member, your ski partner, who you think would benefit or enjoy listening to one of these episodes. Please share it with them, expand the audience. I really love, um, hearing feedback from everyone and each time I'm putting out a podcast, it's growing. The number of you who are listening to the whole thing and responding with questions is increasing. It feels like there's some momentum out there. And now that we've hit episode 20, we have crossed into the top 1% of all podcasts of all time. So thanks for sticking with me. I appreciate your attention. I'm here to serve you and until next time, stay fit, stay focused, and have fun.