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Help Me, I Can't Breathe: Special Considerations W ...
Help Me, I Can't Breathe: Special Considerations With Intubation, Ventilation, and Weaning the Trauma Patient With Severe Obesity
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So, my name's Rich Branson, I'm a respiratory therapist. I've been a SCCM member since 1984, which I learned in my last lecture, which is where I came from. Many of the people in the audience weren't born then. Which reminds me that when you give a lecture about elderly trauma patients, you always have to raise the bar every decade to make sure you're not in that category. I'm on the editorial board, I was on the board of regents and the past chancellor of the college. I've worked in the intensive care unit, surgical and trauma ICU at the University of Cincinnati for over 40 years. That doesn't look better. Okay, so these are my disclosures, companies that I do work with, mostly mechanical ventilation companies or devices for oxygen therapy. Oh, sorry. So, I wanna talk about the differences in respiratory mechanics associated with obesity, list of challenges associated with intubating obese subjects, describe intraoperative management in obese subjects, talk a little bit about the use of esophageal pressure, which is very popular for trying to separate chest wall from lung compliance in obese subjects, talk a little bit about this high-flow nasal cannula and non-invasive ventilation for post-extubation failure in obese subjects, which two very recent papers from Europe are looking at this concept. So, I mean, obesity in the general population is increasing everywhere. According to the most recent figures, 42% of the population is classified as obese that be a migratory than 30, and 9% have to be a migratory than 40. Obesity and respiratory function impacts the respiratory mechanics, chest wall mechanics, compliance. It increases the work of breathing, it reduces gas exchange. Of course, it has cardiovascular complications as well. And there's this obesity paradox that seems to still be hanging around that somehow it appears that some patients who are overweight do better than patients who aren't overweight in the ICU. So I know this one is hard to see, but you're talking, these are the things I'm gonna go over, the management of patients with obesity. So intubation, the things that you can do, and I'm gonna go through these individually. There's been very popular use of high-flow nasal cannula to pre-oxygenate these patients, and then considering a recruitment maneuver after intubation. If the patient develops ARDS or refractory hypoxemia, the way you ventilate the patient might change slightly. ECMO is a challenge, obviously, in obese patients. I think it's important to think about when you have an obese patient, are they being treated for sleep apnea at home? Do they have obesity hypoventilation syndrome? And that might guide the way you make this decision. Extubating patients, make sure you check to make sure they don't have cardiovascular disease, and consider extubating directly to non-invasive ventilation in some patients. I'm gonna show you why I think that's a good idea, and other issues that are outside of my talk, I'm not gonna really spend that much time on. So this recent paper in CHESS by Anderson reviews all of these things we're talking about. Of course, this is my focus. In obese patients, there's a decrease in total respiratory compliance. And that's important, because the lung compliance doesn't fall, typically, it's just the chest wall compliance that's increased. There's a decrease in functional residual capacity, derecruitment of the lungs, ventilation perfusion mismatch is worse, the work of breathing is higher, and there tends to be some increase in intrinsic PEEP. You match this then with the problems with cardiac issues, and you have a patient at risk for respiratory distress after operation or after trauma. This is from a paper by Grassi, who's an Italian fellow that's been working at Mass General and has done a lot of work on obesity. And he makes the distinction that there are some people who have central obesity, so a large abdomen, versus people who have the lower weight, carrying the weight in their hips and their thighs. And these are the differences in, if you remember your pulmonary classes, two volumes always turn into a capacity. So, inspiratory reserve volume and tidal volume make inspiratory capacity. These two capacities make vital capacity. Part of FRC is the ERV and the residual volume. And in patients who have their weight lower in the body, there's not as much change in respiratory mechanics. These are the patients with the distended abdomens who have the largest problem. So, here you see the FRC is reduced, and we might consider end-expiratory lung volume if they're on the ventilator. There's small airway closure, so at every exhalation, the patient's in their closing capacity. There's collapse of alveoli at the end of exhalation, even when they're not on the ventilator. There is increased work of breathing, and tendency to be slightly hypoxemic compared to patients who are not obese. So, this is, I think, a really good graph demonstrating this issue. So, this is a pressure-volume curve of the respiratory system. So, at your low lung volume, down near FRC, your compliance isn't nearly as good. But when you get to the middle lung volumes, compliance gets really good, doesn't take a lot of pressure to create a big volume. And then here's where you take too big a volume and you have a bigger pressure change. You've seen this on ventilator patients. But this is true even during spontaneous breathing. And in a patient who's got severe obesity, this whole curve gets shifted to the right. So, it takes a lot longer before you get to the pressure to open the lung at end-exhalation, and then you get some improvement in lung compliance as you go up. But this impact on FRC is really important. Now, what about intubating obese subjects? And again, preparing for this talk, it's pretty interesting. There have been a lot of studies in the last five years or so, and many in the last year. And this one's by Audrey de Jong, published in British Journal of Anesthesia. It's from the Netherlands, looking at intubation in obese subjects. So, they did a multi-center trial, and they said, well, let's look at intubating patients and tried to use their language. OT is operating theater, as opposed to operating room for us here in the US. And ICU intubation. So, they looked at 1,400 ICU intubations and 11,000 operating room intubations. In the ICU, 20% had a BMI greater than 30. In the OR, 19% had a BMI greater than 30. And here at the bottom, we're looking at, here's the ones in the intensive care unit. These are the number of severe life-threatening complications that these patients underwent. So, in the intensive care unit, it's a huge difference with either no difficult intubation in the front, or a difficult intubation, over almost 60% of the patients have a significant serious adverse event. Now, not being a physician, I get to sit in the room and listen to them talk about each other when they're not around. And so, of course, the anesthesiologists say, we have no problems with intubating, but the emergency medicine and the trauma groups will say, well, that's because you intubate under the best conditions. The patient's quiet, the patient's sedated, the patient's not sick, most of the time. So, I don't think this is very unexpected. Patients in the ICU who needed emergency intubation, the reason they're in the ICU is what puts them at risk for these issues, but it's even greater in patients who are obese. So, here's that from that same study, looking at the number of patients who got direct laryngoscopy with a Bougie introducer, video laryngoscopy, Fast-Trac, or fiber optic intubation. Here's the ICU group, and here's the group in the OR. And again, huge differences in the number of techniques that were used between those two groups, because this group is a much larger challenge. So, they concluded that the incidence of difficult intubation in obese patients in the ICU was twice as high as when the patients are in the operating room, because they're sicker. Severe life-threatening complications related to intubation occurred 20 times more often in the ICU. Most of the time in the OR, intubations are elective. In the ICU, most of the time, intubations are emergent. There are life-threatening complications were associated with both ICU admission and difficult intubation in the obese subjects, and it was more often in the case, in the difficult intubation devices were used more often in the operating theater in the ICU, mostly because it's available, and the anesthesiologists are trained in the difficult airway algorithm. But it's clearly a problem for obese subjects managing their airway. So, there's a lot of discussion about how do you manage the patient in the operating room, and I'll show you a couple studies about this, and Paolo Pelosi and Lorenzo Balk and a couple Italian investigators, part of a multi-center trial, international trial, looking at ventilating patients with obesity, and I know this is a little bit hard to see, and I just wanted to throw it up there all together, is going to be, do you use aggressive PEEP in the operating room? Do you use a recruitment maneuver in the operating room? What FIO2 do you use, and how does that impact the outcome? And the way you manage the patient at risk for ARDS versus with ARDS, what the anesthetic management is, and then the post-anesthesia care, and I'm gonna show you more of this that is more readable, so we'll get through to it. So this has been one of the issues, and this is, I think, a good mechanistic way of looking. If you want to ventilate patients in the operating with a low PEEP and have a minor stress and strain, but increased shunt, so in these graphics, the blue is collapse, the light color is open, aerated, areas of the lung. The red is blood flow, so if there's increased blood flow here, then that means there's increased shunt, and this is the patient at end expiration, and this is at end inspiration. So you see there's not much stress and strain here. If you use zero PEEP, which some people have advocated in the past, but a high tidal volume, at end inspiration, you can over-distend these alveoli, but you can get rid of the collapse, which might be seen as a positive, and we'll go back to this at end expiration. Moderate PEEP and a low tidal volume, I wish we'd stop calling it that. We should just call it a normal tidal volume. Four to six mLs per kilo, that's what you're doing in the room right now, and occasional recruitment reduces lung stress and shunt, strain, and reduces interpulmonary shunt. High PEEP, and in a lifetime in working in critical care, we have done so many studies to normalize a physiologic variable that we were sure was gonna fix the problem that almost universally results in a worse patient outcome. And I think the high PEEP, which increases stress and strain, this is the high PEEP at end exhalation, you have over-distension, you have reduction of blood flow to these alveoli, and it has negative hemodynamic effects as well, because you're collapsing venous return. So this has been the argument for which one of these techniques do you wanna provide. So one of the ideas is, well, we'll just use esophageal manometry, so you place a catheter down into the esophagus, it's an esophageal balloon, it's not much of a balloon, it's usually about this long, and it barely has any air in it, you're just trying to sense the pressure in the pleura through the esophagus, and it is a technique that requires some expertise to place properly, as well as to interpret. And both esophageal manometry and electrical impedance tomography, which is still not available widely in the United States yet, have been proposed for taking obese patients to individualize their ventilation in PEEP. And this is again from the group from Mass General, looking at pleural pressures, non-dependent pleural pressures, so the lung hangs in the chest, and then dependent pleural pressures, where the weight of the chest wall and the lung press on the dorsal part of the lung. So I couldn't in 20 minutes go through every one of these studies, so there are a number of perioperative management trials that have been done, many of them multi-center trials. The Profilo, iProve, and ProBeast trials have all looked at these issues and compared intraoperative trial of high PEEP plus recruitment maneuvers versus low PEEP and no recruitment maneuvers. There was no difference in the postoperative complications. An intraoperative strategy with a higher PEEP and alveolar recruitment did not reduce intraoperative pulmonary complications in the ProBeast trial. And then a meta-analysis of all these trials together that was published in the Register of Journal of Anesthesia this past year showed that the differences in the patients who were involved in the analysis made it difficult, but high PEEP was associated with fewer episodes of desaturation, but far more frequent intraoperative hypotension. This is one of those issues you have to remember. You can increase the PEEP and you can improve the PaO2, but the decrement you create in cardiac output results in a net decrease in oxygen delivery to the tissues, and it's just not worth it. High intraoperative PEEP with recruitment maneuvers during low tidal volume ventilation does not reduce postoperative pulmonary complications. So this is a paper from the Cleveland Clinic that was published in Restoricare last year, and they found that obese subjects in the greater obesity range were more likely to receive a tidal volume of eight mLs per kilo. I think, you know, the old, that person is big, they must need a big tidal volume. But again, the major determinant of lung volume is height, not weight, and that was an odds ratio of three. And obese patients, in their experience, were more likely to get rescue-inhered pulmonary vasodilators, likely because they're not getting as high a PEEP and they have hypoxemia. This is where, again, kind of a methodologically complicated study. They took their group of obese patients, again, a group from the Cleveland Clinic, and looked at the PEEP based on empiric PEEP from the PEEP-FIO2 tables from ARDSNet-ARMA, and looked at the PEEP of those patients if it had been guided by the EP-VENT study, which was esophageal manometry, creating a transpulmonary pressure of greater than one centimeter of water pressure. So there was always some increase in lung volume. And what they demonstrated is that if you use esophageal-guided PEEP, you would normally give a slightly higher PEEP, especially in the patients who are obese. Now this is where we get into the physiologic studies. These are really well-done studies and the authors are experts, but here's a paper from Anesthesiology from 2019, and this is the group from Mass General who spent a lot of time studying obesity in post-operative or intraoperative patients. And this, they're using the collapse and over-distension percent with EIT. So if you've ever seen EIT, it looks like two blobs on the screen and the different colors demonstrate to you where the distribution of ventilation is. And so the white areas are collapse and the dark areas are over-distension, and here's the set PEEP on the ventilator, and they're measuring this, the optimal PEEP, where you have the least amount of over-distension and the greatest or most advantageous prevention of collapse, and that is at esophageal pressure of about one plus or minus three above the PEEP level. And they said that among PEEP titration strategies, setting PEEP according to the decremental PEEP trial, so you go up to a high PEEP and then turn it back a couple centimeters at a time till you find the best compliance. Proceeded by a recruitment maneuver resulted in the best lung function. Notice that they did not say it resulted in the best outcome. So principles of ventilation for obesity then. At intubation, try the patient on CPAP or non-invasive ventilation or high-flow nasal cannula to get them prepped for the intubation. If they don't have ARDS, then we're talking about six mLs per kilotidal volume. Maintain a fairly normal CO2. Again, I wouldn't drive to the CO2. A PEEP of five or 10. Plateau pressure remain less than 20. Driving pressure's less than 15. Only use recruitment maneuvers if they're clinically indicated. If the patient has ARDS, again, still small tidal volumes, allow the PCO2 to rise a little bit. Here, higher PEEPs. And again, hopefully I'll show you a picture that will make sense to all this. But you still do the lung protective strategies. Increase the FiO2 if you have to to maintain the SpO2 in the proper range. Obese patients can be placed in the prone position. It gets done all the time and should be done if their PF ratio is less than 150. So this is one of the big questions. I think it was part of the title. I didn't submit this talk or anything. That was just asked to provide it. So spontaneous breathing trial, we know as part of the A to F bundle, looks at can the patient be successfully extubated? And the goals are to liberate the patient, find the criteria to liberate the patient early and to have a successful extubation or liberation. The goal of an SBT is not to pass it. The goal is to remain extubated if you decide that the SBT says so. And I think back to this. Amongst injustices, I guess, across medicine at time, most people think of the spontaneous breathing trial and the frequency tidal volume ratio as something that Martin Tobin popularized. And the paper in the New England Journal was Carl Yang was the first author. You never hear it called the Yang Index, by the way. And what they did is they took patients off the ventilator, just disconnected them from the ventilator, and they put a right to respirometer on the ET tube and they watched them breathe the room air for a period of time and measured the frequency to tidal volume ratio. And I'm gonna show you how that, why that's important. So this is, again, from that group in Italy in Mass General with Grassi as the author. This is the esophageal pressure, these big wide swings, and this is airway pressure in a patient on a spontaneous breathing trial. And as you switch that patient to a high level of CPAP to breathe spontaneously, so over here we're on a little less than 10, here we're on 20. Because you're recruiting the end-expiratory lung volume, you're preventing the collapse of alveoli at end-exhalation and breathing into the closing capacity, the work of breathing in the patient who is obese is much better. And this is great, but again, I'll tell you, the goal, if you wanna do this, that's fine, but if you extubate the patient from this value, you better be prepared very quickly to provide that value with a CPAP mask or non-invasive ventilation. Again, the goal is not to get the patient to pass the study, the goal is to get them extubated. So again, one more study that I think is pretty important, they look at spontaneous breathing trials, sorry, spontaneous breathing trials and work of breathing post-extubation, and they did pressure support of seven and a PEEP of seven, no pressure support and PEEP of seven, seven and no PEEP, zero and zero, the use of a T-piece, and then what happened during extubation. And again, I'm just a little bit, you know, a lot of data on the screen. Here's the seven and seven, zero and seven, seven and zero, zero and zero, T-piece and after extubation. And what an SBT is trying to do is find out this right here. So which one of these over here was most likely to look like this? And if you look, it's the ones that have the least level of support. So you have to be careful if you're gonna use some pressure support and PEEP during your spontaneous breathing trial, and it goes away, post-extubation, your patient's gonna have a significantly increased work of breathing, a reduced FRC, probably hypoxemia, and the answer is to use CPAP or non-invasive ventilation, and in some cases, high flow nasal cannula. A little, just from the same trial, looking at, if you don't know anything about esophageal pressure, all you have to know is the greater the number, the harder, the more the patient's working. So on the high PEEP and high pressure support, on only seven, on no PEEP and seven, and pressure support, 13, and as you move across here, here's, again, this is what we wanna see after extubation. So these techniques that don't provide as much support are better at telling us what the patient's work of breathing is going to be like post-extubation. And then I'll, last two slides, this is a really recent paper from Critical Care, Intensive Care Medicine, looking at effects of post-extubation, non-invasive ventilation, with active humidification versus high flow nasal cannula, and re-intubation patients, very high risk for extubation failure. Again, the technical part of mechanical ventilation, high flow nasal cannula has been, especially during COVID, everybody thinks high flow nasal cannula is great. One of the reasons high flow nasal cannula is so well tolerated is the heat and humidity that's provided. Oftentimes, when we do non-invasive ventilation with a face mask, with a ventilator that's not an intensive care unit ventilator, it doesn't have a humidifier on it, and you just get basically room temperature, heat and humidity, and it's a real issue. It dries out the airway at these high minute ventilations. So, again, I give these guys credit for something that we've been talking about for a while. Dr. Rocha and Louis Blanc, I'm in his group from Spain, looking at, these are patients at high risk for extubation failure, so BMI greater than 30, on the ventilator for longer than seven days, hypercarbia, known difficult weaning in the past, laryngeal edema, Apache greater than 12, and mostly being ventilated for a cardiac reason. And here is the effects of high flow oxygen therapy on the bottom, and these are patients who are failing and having to be re-intubated versus non-invasive ventilation. This is really different than most of the other data that we've seen comparing NIV to eight high flow nasal cannula but I really believe it's because they provided the heat and humidity. If you've ever had to intubate a patient who's been on non-invasive ventilation for a day and hasn't had any humidity, as soon as you put the laryngoscope in, the tissues are all friable and dry and they bleed easily. And I think it's something we have been ignoring because, quite frankly, it's more complicated to go get a heated humidifier or find one for a non-invasive ventilated patient. And they followed that up with this other trial, another analysis in the Journal of Intensive Care, and they're looking at the risk factors and the odds ratios of being re-intubated. And the BMI greater than 25 certainly contributed. But again, I'll show you overall absolute risk of re-intubation, much lower with non-invasive ventilation in green than high flow nasal cannula in blue. So post-extubation obese patients, non-invasive ventilation that includes CPAP or PEEP with heated humidification is, at least in these two studies, better than high flow nasal cannula, which has not been the case in patients with hypoxemic respiratory failure without obesity. So I'm gonna leave you and say, obese patients certainly have alterations in respiratory mechanics. Physiologic studies tend to favor high PEEP in the use of recruitment maneuvers, but aggressive interoperative PEEP and recruitment maneuvers improve surrogate endpoints, but not important outcomes. Remember, the first three days of the ARJNET-RMA trial, which was six mLs versus two mLs per kilo, the patients in the HITOTOL-M group had a much better lung compliance and a much better PaO2. They also died 20% more often. So just because there's a physiologic improvement doesn't mean it's what we should do. Obese subjects are, of course, at risk for extubation failure. There's no evidence that using a high PEEP during SBT improves liberation success. It improves the success of passing the SBT, but not the patient staying off the ventilator. And I think these post-extubation obese subjects have an increased risk of re-intubation and non-invasive ventilation with heated ventification appears to provide an advantage in those patients. Thank you.
Video Summary
In this video, Rich Branson, a respiratory therapist, discusses the differences in respiratory mechanics associated with obesity and the challenges of managing obese patients during intubation and extubation. He highlights that obesity has a significant impact on respiratory function, increasing the work of breathing and reducing gas exchange. Obese patients are also at a higher risk for complications during intubation and have a higher risk of extubation failure. Branson discusses various strategies for managing intubation in obese subjects, including the use of high-flow nasal cannula and recruitment maneuvers. He also suggests considering factors such as obesity hypoventilation syndrome and sleep apnea when making decisions about patient care. Additionally, he emphasizes the importance of using appropriate PEEP levels and heated humidification during non-invasive ventilation in post-extubation obese patients to reduce the risk of re-intubation.
Asset Subtitle
Pulmonary, GI and Nutrition, 2023
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Type: two-hour concurrent | Trauma Strategies: Patients With Severe Obesity in the ICU (SessionID 1227137)
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Pulmonary
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GI and Nutrition
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Airway Management
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Obesity
Year
2023
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obesity
respiratory mechanics
intubation
extubation
gas exchange
patient care
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