My name's Craig, I'm from Emory in Atlanta. It's really inspiring to see so many people here. The Physiologically Difficult Airway is a concept that's really near and dear to all of our hearts. You know, we have a worry in the back of our mind that it's not kind of, you know, penetrated our active thought, you know, kind of around the world. So thank you, everybody, for coming. You found the best panel today, for sure. Maybe at the whole Congress, TBD. Just so I can help everybody to get the most out of your time, if you're a nurse, put your hand up. Nurse who's not yet an APP, just kidding. If you're an APP, put your hand up. Okay, physicians. Okay, respiratory therapists, respiratory therapists. Okay, hey, pharmacists, any pharmacists in the audience? Okay, fantastic, that was very helpful. At the least, we've all reduced our right upper extremity DBT risk, so thank you. I don't have any relevant disclosures to what I'm about to talk about. As Sheila just told us all, in the intube study, and we'll come back to this, hypoxemia was the second most common complication during emergency airway management. Hypotension was the most common complication, so we buried the lead a little bit. That's gonna be next. I'm gonna talk about why patients become hypoxemic when we intubate them, and what we can do to help temporize it. I'm gonna cover a lot of peer-reviewed literature, and you're gonna think to yourself, maybe along the way, like, how are we gonna synthesize all of that? I promise that we will conclude with very practical take-home tips that you can implement in your ICU, in your practice, later today. I promise we will do that. Along the way, we're gonna recap some data from intube that Sheila just told us about, but specifically through the lens of hypoxemia during emergency airway management. Again, 9.3% of patients in this very large, kind of landmark, prospective observational study had an oxygen saturation of less than 80% during airway management. And you may be wondering to yourself, does it matter? So Sheila just showed us this graph. I'm gonna blow it up bigger. So here's the probability of survival out to 28 days in patients who had hypoxemia during airway management versus those who did not. And what you'll see is that, again, there's this non-statistically significant higher risk of mortality out to 20 days. Again, hypoxemia was not a super common complication, 9.3%, right? Compared to cardiovascular instability, 45%. One imagines that with a larger sample size, right, that this signal could pan out to be statistically significant. I also think we all know that transient hypoxemia during airway management is bad. I think, and although I'm not gonna ask anyone to put their hands up now, I'm sure this has never happened to any of us individually, we've all seen someone's oxygen saturation get quite low during airway management. And if you've ever had that experience of you're trying to find the airway, you hear the oxygen saturation start to go down, the tone of the pulse ox changes, then the beeps aren't as frequent, and then someone's saying, get the backboard. It's never happened to any of us personally, but we've seen it, we've seen it. I guess what I wanna kinda emphasize here, and we'll come back to this in a minute, transient hypoxemia during airway management is probably not benign. Just as we've seen that even transient hemodynamic perturbation during airway management impacts 28-day mortality, the case is probably the same with hypoxemia. And in the best case scenario, our performance as humans doing a complex technical skill decreases the more anxious we get, and there's nothing like the oxygen saturation going down to make you tachycardic. So just something to keep in mind. Why do we see hypoxemia in critically ill patients? If you think about all of the causes of hypoxemia that are kinda possible under the sun, the two that we see most commonly in the intensive care unit are by far VQ mismatch and physiologic shunt. And if I just kinda pull those out and we focus on these two for a minute, I guess what I wanna emphasize is that with VQ mismatch, you're gonna get some response to increased FiO2, but the problem with physiologic shunt, as we'll explore graphically in just a minute, is you get a really marginal or sometimes no response to more FiO2. So again, like this is a very kind of like common graph I'm sure we've all seen from a textbook. Looking at what happens is the shunt fraction goes up. So if you have a patient with a shunt fraction of 30 or 50%, you get, oh, I'm so sorry. You get essentially no response in your PaO2 to going up to 100% fraction of inspired oxygen. And I'm gonna get to why this is important in just a second. This is one of my favorite all-time papers in airway management. I've never met this individual, but there's somebody out there called Tom Mort. Tom Mort, if you're in the audience, will you put your hands, today's not my day. Tom did a study. He's done published a few early kind of seminal papers in emergency airway management. Tom did a study where he drew ABGs at a baseline and up to eight minutes of 100% FiO2 pre-oxygenation on the series of patients that he intubated in his ICU. And here's what happened to their PaO2s. Nothing, absolutely nothing happened, right? The average PaO2 was 60 to begin with, went up to 90 after eight minutes of 100% FiO2 pre-oxygenation. That's not enough. That's not gonna buy you any additional time to manage the airway. So we need positive pressure in patients who are critically ill with bad lung function to pre-oxygenate them effectively. Not all patients, we'll talk about kind of a stepwise approach to this in a little bit, but I guess what I want everybody to take away is that a lot of our airway management approaches that we use in the intensive care unit have been adapted from the operating room where patients walk in off of the street, breathing room air, doing fantastically. We pre-oxygenate them with 100% FiO2 for a little bit. The PaO2 goes up to 300 or 400 or 500. They can be apneic for three, four, or five minutes and everything's totally fine. In the ICU, I think we all know this, that's not the case, right? We have VQ mismatch, we have an enormous amount of shunt. And just applying FiO2 without positive pressure is not gonna do you or the patient any favors. So if we need positive pressure, right, what are the two means by which that we can accomplish that, you know, practically speaking in the ICU when it comes to airway management? We have non-invasive ventilation, we have heated high-flow nasal oxygen. I'm not gonna belabor that point. You know, we use these modalities for respiratory failure all of the time. The extent to which we employ them specifically when we're preparing to secure a patient's airway is variable. So one of the little data points from Intube that I'm not gonna cover is that the use of non-invasive ventilation and high-flow nasal oxygen for pre-oxygenation in Intube was very low, like less than 5% of all airway management encounters in Intube for both of these different modalities. I think we all know that you can do a lot more with non-invasive ventilation than we can do with high-flow nasal oxygen, right? You have a much more reliable interface, you're able to deliver more PEEP, you have granular control over FiO2, all of that's fantastic. I don't know about you all, I can't intubate through a mask. I haven't figured out how to do it yet. So high-flow nasal oxygen offers the benefit, right, of being able to use it not only as a pre-oxygenation modality, but also to provide some apneic oxygenation while we're, you know, securing the airway. The problem, the problem is that when we look at the, when we compare non-invasive ventilation, and here a heated high-flow nasal cannula, right, HFNC, CO2 is conventional oxygen therapy. So this is one of many meta-analyses, we'll talk about one, another one in just a second, looking at the impact of non-invasive ventilation versus conventional oxygen therapy on the incidence of desaturation, so saturation less than 80. And what we see here is that non-invasive ventilation pans out very favorably, your pooled effect estimates down here, compared to conventional oxygen therapy. But when we look at heated high-flow nasal cannula compared to conventional oxygen therapy, the signal is not as clean, it's not as convincing that high-flow nasal cannula is as impactful at keeping the sat from going down. And you say to yourself, okay, this is one meta-analysis, like why might this be? Let's look at another meta-analysis, and again, in a subset of studies looking only at ICU patients, we control, or when we compare high-flow nasal cannula to conventional oxygen therapy, same thing, we see a confidence interval that crosses unity. Why might this be? And I think that the answer has to do with how sick the patient is. So in the FLORALI-2 trial, looking specifically at the patients who had a starting PDF ratio of 200 or less, so that's kind of moderate to severe ARDS, when we look at the incidence of desaturation during intubation, what we see is that we had the difference here between heated high-flow nasal oxygen and non-invasive ventilation, and then when we adjust for PaO2, when we adjust on the baseline, you know, the respiratory failure severity, we see that this difference winds up being statistically significant. And when we take all of the studies that have been done, comparing high-flow nasal oxygen versus conventional oxygen therapy, what we see is that the relative risk of mitigating hypoxemia is proportional to the patient's starting PDF ratio. In fact, there's an almost linear relationship, right? So like over here in the PROTRACH study, for example, where the patient's starting PDF ratio was quite good, right, like quite high, high-flow nasal oxygen was very effective at preventing desaturation. If we look up here at FLORALI2, right, these are the patients, this is the subset of patients with the starting PDF ratio of 200 or less, that we didn't see that impact of heated high-flow nasal oxygen. So I guess what I want everyone to take away from this is that non-invasive ventilation is probably better at keeping the SAT from going down compared to heated high-flow nasal oxygen. But of course, we can do things with heated high-flow nasal oxygen that we can't do with non-invasive ventilation. And the effectiveness of heated high-flow nasal oxygen is gonna be relative to the degree of lung dysfunction. I'll come back to this in a minute. Eagle-eyed viewers may notice that there is a dot that lies well outside of all of these other dots in this linear relationship, which is the OPTI-NIV study. The OPTI-NIV study addressed, or tried to address, I think it effectively addressed a very interesting question. What if we do both? What if we apply heated high-flow nasal oxygen and we do BiPAP at the same time? And you say to yourself, that sounds crazy, but you can do it. It's not the easiest thing in the world to get a mask seal around a heated high-flow nasal oxygen interface. But out of all of the studies that have ever been done, you know, looking at ways to temporize hypoxemia during airway management, the OPTI-NIV study had the patients with the lowest baseline starting P to F ratio, 122, and demonstrated that this combination intervention was very effective, much more effective than noninvasive ventilation or heated high-flow nasal oxygen alone. If that sounds crazy, you can also employ a changeover method where you start with the mask interface, you swap over to high-flow nasal cannula. I've tried it. It's hard, right? It's hard. There's a delay, right, in doing that. And as we'll explore in a little bit, getting the tube in quickly and successfully on the first attempt is super important. So that, I think, has got some downsides associated with it. But if you practice two hands with a mask interface, you can get a seal around heated high-flow nasal oxygen. And we'll talk about instances in which applying this might be a particularly good idea. I don't know about you all, but when I was kind of growing up in critical care and in anesthesiology, it was considered very bad to mask ventilate patients who were anywhere other than in the operating room. We didn't do it in the emergency department. We certainly didn't do it during trauma. We didn't do it in the intensive care unit. The idea was that the patients were all gonna aspirate and they were gonna die. Heaven forbid if we ever squeezed the bag. There've been two studies to kind of look at this practice. Prevent was probably the biggest and the best. It was published in the New England Journal of Medicine a few years ago now. Not surprisingly, if you apply a mask and you squeeze the bag, the oxygen saturation goes up and stays up compared to if you don't do that. And one of the main findings from Prevent was that there was no signal for harm that emerged from that study. So, and again, kind of in an unselected med-surge ICU population, kind of all comers with some patients from the ED, right? Suggesting that this practice of squeezing the bag is unlikely to kill your patient, but is likely to keep their oxygen saturation up. And again, when we take data from Prevent and another study fellow, and we compare this again, not surprisingly, in patients who got bagged during, right? During the airway management encounter, the oxygen saturation stays higher. So this is the practical point of the lecture. So if everything I just told you is like, oh, it's too many figures, like this is the practical portion of the lecture. Okay, so here's what I would say. In the intensive care unit, we have to take an adaptive pre-oxygenation approach. So if the patient's starting P to F ratio is greater than 200, so mild ARDS, or just respiratory failure for other reasons, lung function is okay, we can do what we usually do, right? In these patients, we have reasonable evidence to suggest that heated high flow nasal oxygen and conventional oxygen therapy probably are the same when it comes to preventing desaturation during airway management, which I mean, SpO2 less than 80%. Don't be afraid to employ bagged mass pre-oxygenation in these patients, right? We've got, again, we've got good evidence from two trials now to suggest that, again, in an unselected cohort, the critically ill adults, that it's a safe practice. All right, so P to F ratio greater than 200, we do what we usually do. When the P to F ratio starts to drop below 200, and let's say we're in that 200 to 100 range, here's what we should be thinking. In these patients, again, we know when the P to F ratio drops below 200, heated high flow nasal oxygen and ergo conventional oxygen therapy are not as effective at keeping the setup as non-invasive ventilation. So in these patients, we need to think about pre-oxygenating them with non-invasive ventilation. Many of them may be on non-invasive ventilation to begin with. Fantastic, leave it on, pre-oxygenate. But if they're not, even for the purposes of securing the airway, you should think really hard about putting a mask on. And we know in these patients, especially if you're anticipating difficulty, that there are risks for desaturation during airway management. It might be smart to have heated high flow nasal oxygen around either to do a changeover method or maybe the combination. If you have the misfortune of securing the airway in a patient with really, like you walk in, you come in in the morning, somebody's on AVAPs at 100%, and you look at the blood gas, PO2 70, and they're struggling, you're like, ugh. So these patients are at the highest risk for badness. So these are the patients where non-invasive ventilation ideally with the combination of heated high flow nasal oxygen, it's gonna help keep them the safest and help keep you the calmest and the happiest during the airway management encounter. And I guess the other thing I would say is that along the way, we have to employ some other best practices. Elevating the head of the bed, not being afraid of apneic or rescue ventilation with a bag. Also put a plug out there that in patients when the respiratory failure is really severe, that securing the airway awake is an approach that can be applied, has a lot of practical and technical challenges that's associated with it, especially if that's not been part of your training continuum, but certainly an option that's out there. I want to conclude with this. And although this is not a talk about laryngoscopy or how to get the tube in effectively, the more attempts that we take to put the tube in, this is from the supplement of intube with it kind of like buried in there, which makes me feel very sad. As we take more and more attempts to secure the airway, the incidence of hypoxemia goes up. I know that that sounds maybe silly, but one of the things that we can do to help keep patients from desaturating is to employ best practices when it comes to securing the airway on the first attempt every time. So in addition to pre-oxygenation, we also have to keep in mind the importance of first pass intubation success in these patients. So that's all I have to say. Employ a risk stratified approach to pre-oxygenation. Don't be afraid to squeeze the bag. And don't forget about optimizing the likelihood of first pass success. If you have feedback on the lecture, you can email me and thank you very much. Thank you.

hypoxemia

airway management

non-invasive ventilation

pre-oxygenation

intubation success