Okay, game on. My name is Anya Appalodepe. I'm coming to you from Washington University. And I wanna talk to you today about the ability to use point of care ultrasound to optimize mechanical ventilation and guide diuresis in patients with acute respiratory failure. So no disclosures. I'm grateful for those who shared slides with me. So should ultrasound be used? Can ultrasound be used to optimize mechanical ventilation and guide diuresis? Surely in this age of COVID and lots of patients who have mechanical respiratory failure, this is an important question. So I'll break this down into sort of three ways to think about being able to optimize your pulmonary mechanics and or guide diuresis. That is direct evaluation of the lung itself, thinking about the infrastructure, such as the diaphragm and then the supporting cast, I call it, looking at the heart, specifically diastolic dysfunction. So let's start with the lung. So there are several transducers that we can use. We have to first know exactly which one to use when imaging either the heart, the lung or the diaphragm. Usually we'll use sort of these lower frequency probes to think about questions like, is there water in the lungs or to evaluate the heart itself and higher frequency probes to look at more superficial information, such as pleural pathology and or diaphragm pathology. And of course, if you have something in between like a micro convex, great. There are lots of protocols for evaluation of the lung and it could be, think of it in several ways. So there are sort of option one, which may be to just look at three areas of the lung where you're looking at what I call zone one, zone two and zone three, which might just be the anterior, the mid axillary and then the posterior lung. There's additional to look at more of the lung, looking at essentially four on both sides, which will eight and then six on both sides for a total of 12. Certainly we know that the more of the lung you can see sonographically, the more you can have a more complete assessment of what's going on with the lung, but the time and context may delineate or may dictate exactly which protocol of lung imaging you may choose to do. So again, thinking about these zones, the amount of them, it's also important to think about the pathology that perhaps you're looking for to help decide where you should look. So if you're looking at pleural pathology, you wanna know there's pneumothorax, you wanna be in the anterior zones, essentially zone one. And if you have questions here about perhaps is there consolidation or alveolar processes, you wanna be more at zone two or zone three. So effusions, alveolar consolidation, and then posterior fields really to look for alveolar consolidations. You might see some smaller effusions there. This slide is very important for understanding lung pathology. And I know a lot of you guys already using this concept that we know that the air and fluid ratios help us to understand exactly what we see on the picture from a pneumothorax evaluation all the way to alveolar consolidation and total effusion evaluation. Starting first with pneumothorax is one of the ways to certainly when patients are ventilated to optimize them or make sure they don't have a pneumothorax is to use lung ultrasound. We know that there's very good sensitivity for lung ultrasound versus chest x-rays, especially for anterior pneumothorax season, especially for patients who are supine. Understanding the physiology of why that works, we'll start with an actual ultrasound clip. So this is a CT scan with this x-ray here, and this is what a normal would look like. So we're using a high-frequency probe. We first identify the pleural line at the level of the rib. We can see it's bright hypercoic and goes back and forth. We know that's the parietal and visceral pleura moving against itself. And at this part, at the exact point where the probe is, we know that that's useful to exclude there being a pneumothorax. Let's compare that to a picture that might look like this, right? So still a high-frequency probe we're using so we can get really good pleural resolution identified here by a rib to know that that's definitely the pleura. And we can see tissue movement, but no actual movement of the pleura itself, suggesting that there likely, in the right context, is air between the parietal and visceral pleura. And again, context is very important so that you consider there are reasons why the pleura may not move, but it is not related to a pneumothorax. What about this x-ray? If you've not seen it before, then good for you, because I have this problem frequently in our ventilated patients. Question here is, do I need to bronch them? Do I need to increase the PEEP? Or do I need a chest tube because there's a large pleural effusion? Or maybe there's multiple of those processes. Grabbing your probe, using a lower-frequency probe to answer questions about effusions is gonna be really easy to do and important. So first I'm gonna identify the diaphragm. And traditionally here, when I place a probe in that space, I find the diaphragm in a solid organ. And then if there's a large fluid collection here, I will see it, especially if it's large enough to opacify one of the chest cavities that will look like so. It is also important because oftentimes it may be challenging to really see if there's a large or smaller effusions. I think larger effusions are easy to see. But smaller effusions, we know that we use this concept called the mirror artifact to tell there's an effusion in the pleural space. But I do wanna bring your attention to another concept called the spine sign, if you're not familiar with that, which can be useful as well to determine if there's fluid in the chest cavity or not. So at first identifying your diaphragm, again, this hypochoic line and then the solid organ to the right, you'll see that the spinal shadow is seen beneath it. It's also got a bright hypochoic area horizontally. And at the level of the diaphragm and that brightness, if there's any extension of the spinal shadow to the left, you can be reassured that there's definitely fluid in the chest. It can be a large amount of fluid or small amount of fluid, but in any amount of fluid will show demonstration of the spinal vertebral bodies to the left side of the screen, past the diaphragm if there's fluid there. And I think that plus the mirror artifact can really reassure you to know if there's either fluid or consolidation there. So what about if you do determine that you find fluid there, there are some clues to determine what kind of fluid it is. Quick punchline here is that if you've got a lot of echoes in your pleural effusion, it's likely an exudate. There is some good literature to help us distinguish between the two. What about something like this? I am looking at the diaphragm, which is right here in the solid organ to the right. Here's the lung that's compressed. There's a pleural effusion that's here, moderate to large in size, and it's got a lot of echoes in it, suggested that this is probably an exudate. What about looking at consolidations of pulmonary edema? Certainly we've seen this kind of CT before, especially with our COVID patients or other patients with ARDS, you've got this patchy heterogeneous processes that are seen on CT. And sonographically, it's gonna look the same, that starting with normal lung, we expect to see maybe one or two B lines. And B lines, remember, are those artifacts that are suggestive when lung and water interfaces are at the interstitial level, and it's gonna go all the way down to the bottom of the screen. So in our normal lung, we might see one, but as we start to have pathology within our lung spaces, either from infection or inflammation, you start to get more B lines suggesting that there's more lung water present, and we can see that. And of course, really filling between the pleural spaces really lets us know that at the place where that probe is, there's a lot of lung water present. Visually here, seen on an actual clip, is this here on between rib spaces. I'm using a lower frequency probe for this evaluation, and I see one or two, maybe three B lines start at the bottom of the screen for the B line because it should not fade, and it will give you better diagnostic accuracy there compared to this one here, where starting at the bottom of the screen, it's completely whited out, essentially. There's a full diffuse area of lung water that's present, and I'd have to think about what's going on contextually with the patient to understand why that lung water is there and what I could do about it. So we know that B lines are very sensitive, but they lack that specificity. So whether it is diffuse or it is focal and where it is located can help you understand what's the cause perhaps of those B lines and the physiology that's causing it. Other ways that we can think about using lung ultrasound in evaluation of patients who have mechanical ventilation is to score them. So if you choose to do the approach where you're gonna do 12, you're gonna look at six views on each side of the lung, you're gonna get essentially 12, and you can score each of them from zero to three, zero being normal lung, and then all the way to three where there's consolidation, depending on which zone or place that you are. So minimum score of zero, maximum score of 36. And there are some machines that have this overlaid already for you so that you can place it to get a sense. In general, we know that there's less likely to be improvement and some mortality effects when those lung scores are in the high 20s. Again, location of where the pathology is, whether it's consolidation or interstitial syndromes, whether it is unilateral like in a pneumonia versus bilateral like with ARDS, that can be a clue when we're doing a lung ultrasound at each of the zones to understand exactly why we're having or what's the physiology of that problem. Here's an example of what that lung score might look like. This is a patient with a lung score of 11. Here, we're using a higher frequency probe and we see some plural reflections coming off. A little bit more here at these left side zones here compared to the right, a better score of 11. Generally, it's not too high. You saw that PF ratio versus somebody here where the PF ratio is quite low and you can see it's quite diffuse in multiple places where there's evidence of lung water with those B-lines and a score of 27, suggesting that there's pretty diffuse disease and a lot of work needing to be done to optimize mechanics for this person. Well, how can you optimize those mechanics when you see these diffuse B-lines? There are some papers suggesting that you can use titration of your PEEP on mechanical ventilatory support to determine the optimal place for recruitment. This is talking about increasing your PEEP and you are doing that with first B-lines present, increasing your PEEP, excuse me, and then waiting for there to be resolution of those B-lines and taking over from a B-profile because they're B-lines to an A-profile where those horizontal reflections of the plural called A-lines are seen. The studies look pretty decent. Whether or not a lot of people do this is a different question. And of course, thinking again about the entire context of the patient that perhaps there's hemodynamic effects that occur as you titrate your PEEP or right-sided pressure pathologies that occur as you titrate your PEEP. So you're doing it all together optimally to find the best place to have just the amount of appropriate mean airway pressures without any sequelae or negatives of over ventilation. Okay, let's talk now about the infrastructure or diaphragm ultrasound. And are there opportunities for us to use that to optimize mechanical ventilation or guide diuresis? Probably not so much diuresis with diaphragm support unless perhaps you see other pathology that's present. The first thing to note is that diaphragm dysfunction is pretty common and it's not surprising to us. Many of our patients, again, in this COVID era have long periods of deep sedation, long periods of mechanical ventilation and neuromuscular blockade. These are all things that we know cause general weakness of every muscle, including the diaphragm, which is a muscle. That dysfunction though is supported with both the cause of it is being a long mechanical ventilation, but also can then prolong mechanical ventilation itself and cause ventilator weaning. And so are there ways that we can look at the diaphragm to help us determine who's likely to be able to be liberated from the ventilator or optimized on the ventilator? Of note, you can, in some institutions, order a diaphragm ultrasound if you're not able to do this yourself in point of care. And I think that in general point of care, diaphragm ultrasound is pretty new to the party and not a lot of people are doing this or have confidence in there, but there are certainly several papers that suggest that this can be done. And I think as we do things and get more familiar, then we can find the appropriate application for us in clinical practice. So you can look at the motion of the diaphragm in general, when there's a weak diaphragm, it doesn't move a lot. And so the amplitude of that is generally very low where there may be evidence of paradoxical movement, which is suggestive of paralysis and seeing that perhaps more unilaterally might be more convincing that that's what's happening here, looking at the amplitude and the force and the velocity. And then one that's typically talked about is the thickness or this thickening fraction, which is this equation listed here. In the literature, what I have seen is that the amplitude of greater than 25 millimeters and this thickening ratio of greater than 30% are all suggested that patients have good diaphragm movement and may be the ones who will tolerate successful extubation. How do you do it? Typically, we may be using a low frequency probe and I'm showing you two examples here. One is looking at diaphragm thickness and the other one is looking at diaphragm excursion. So for thickness, we're coming here to the mid axillary line where identifying the diaphragm and it's hard to see the diaphragm if you're not doing this frequently. So this will need some practice. On the next slide, I'll show you a more zoned in picture of what the diaphragm looks like. And essentially we're measuring it during inspiration, expiration. We're looking for the thickening of the diaphragm and using that equation to determine if the thickening is appropriate. Diaphragm excursion, I think is probably a little easier. We may have all been doing this qualitatively but not quantitatively. Essentially in this here for quantitatively, you would look at the diaphragm, look at its excursion or movement, especially when you're able to see it against the solid organ and seeing if there's good displacement of the solid organ. You can put a motor rate and it really looks a lot like TAPSE, right? Where we're looking at just the distance displacement of the diaphragm and the solid organ and essentially measuring the peak to the trough of that. And that movement helps us be reassured that the diaphragm is functioning normally during respiration. Identifying the diaphragm, as I mentioned, is challenging if you haven't done it before. Here we're using a high-frequency probe to identify the diaphragm. And the diaphragm, in terms of anatomy, remember it's made up of these pleural layers as well as a peritoneal membrane and sort of has these three stripes when you identify them. You're looking at it during normal rest, inspiration, expiration, as well as perhaps more aggressive inspiration and expiration looking to look at the thickening of that diaphragm, just like every other muscle that thickens in order to work. And so the measurement of the baseline versus with exertion is what, or with thickening, excuse me, is what we're comparing to and determining if the diaphragm is working or not. And again, the number, remember here, in some studies has been at least 30%. At rest, it's 15 to 30%, it's normal. And then with maximal effort, at least 20% is suggested to be helpful. There are a few studies that talk about its ability to predict weaning from the ventilator. These studies are a little bit older and the best ones that I could find. And again, it just has to do with, do we use this number in isolation to not give people chances to have ventilator liberation? I'm not sure too many people do. And again, I think for myself, using these fractions, these thickening fractions are probably more useful when you see evidence of asymmetry from one side to the other. And in all these studies, when the diaphragm was working properly, people were more likely to be extubated. And that probably intuitively makes sense to us. Here's a final picture just showing you, again, diaphragm ultrasound. And again, this is, you have to look at the context because it depends on this excursion of the diaphragm. Is it with passively breathing? Is it with voluntary sniffing where there's more of a big uprise? Or is it with a nice deep breath that sort of looks like some waveforms that we've seen before, perhaps like with entidal? But I think what is important is that in each of those, there's gonna be an uprise. And what may be obvious or noticeable is that when you have evidence of paradoxical or paralysis, that motion is actually going to go downward instead of upward. And that may be something visually that we can see easily. Okay, finally, to the supporting cast for ventilator optimization, as well as to guide diuresis, how does the heart affect this? So we know that in acute resuscitation, people are gonna get fluids and fluids are good for them for the portion of the resuscitation that occurs. But on some point we have to deescalate, we have to remove some of that volume or perhaps strategize so that we don't even get overloaded. If we do, are there ways sonographically looking at the heart that we can assess that? Well, it's important for all patients, but especially important when patients have evidence of CHF that's not related to systolic function. So first looking at this picture here, we see a pair of short axis view and this heart does not look like it's ejecting much. This person clearly has reduced EF. And probably for most of us, if we put the probe on to look here, we're not gonna give this person a lot of fluid. And I think that that's probably appropriate. But the next patient here, which looks like they have LBH and looks like systolic function is preserved. The issue is that maybe a lot of us would give fluid to this person, but unfortunately this person also has evidence of heart failure and would likely decompensate with aggressive fluid resuscitation because they have preserved ejection fracture but have inability to relax and have diastolic function. If you're thinking about, well, who might have diastolic dysfunction? Here's a nice little scoring system that I saw that I thought is useful for us to think about who we should be worried about. Those are patients who have a fibrillation, atrial fibrillation, pulmonary hypertension, those who might be larger or older. And I especially think about patients who have LBH as another group where you should consider that there's a possibility that they have diastolic dysfunction and assess for that. So how do we determine diastolic dysfunction and why again, is it so important? We're so used to looking at the right side to see if the right atrial pressure is low, like here where the IVC is nice and small compared to when we're looking at an IVC here that might be large or plethoric. And that's really a good information for the right side of the heart. But the reason why it's equally important to pay attention to the left side of the heart is because when I do have high filling pressures, that means the blood is not moving forward. It's gonna back up. And when it backs up, guess what it backs up to? It backs up to those lungs that are being ventilated with the machine and we're providing mechanical support. And so optimizing the filling pressures and the volumes here and diastolic volume and pressure here on the left side is equally important to optimizing pulmonary mechanics and is useful for helping us guide diuresis. Some of the literature for how to really determine if somebody has diastolic dysfunction is based on several markers, okay? So taking it straight from the ASC guidelines, we're looking at this concept of E to E prime and what the average evaluation of that is. I'll explain that in a second. Looking at tissue movement during diastole, looking at TR velocity to determine if somebody has pulmonary hypertension and then looking at the size of the LA if it is large. And look at the ratio here. It's not that you have one and you definitely have diastolic dysfunction. It's just that diastolic dysfunction is complicated. So it's not a great test for just easy point of care in terms of you just look. You have to do quantitative assessments and perhaps serialness of it to be able to really get it right. So if you have more than 50% positive, you're more likely on the diastolic dysfunction spectrum. And if you have less than 50%, you're more likely on the normal spectrum. How do you do E to E prime? First of all, what is it? So it's simply measuring blood velocity over tissue velocity. So when I get a stroke volume of 70 CCs per beat, that means that my tissue needs to move a certain amount to be able to take that 70 CCs I'm putting in there. A ratio that is high suggests that the tissue does not move enough for the amount of blood that's going in there. And that is part of a diagnosis of meaning that I have high LV feeling pressure and diastolic dysfunction. How do I do it? I'm gonna take pulse rate Doppler first here, put at the tips of the mitral valve and I'm gonna measure that first velocity during early diastole called the E wave. And then I'm gonna look at the tissue equivalent movement. Those are called the E primes and they're at the bottom of the baseline. Here's what it looks like on an actual picture. So here's the E velocity during early diastole of blood and then the tissue equivalent during early diastole here, it gives me an E to E prime here of nine. So there are some guidelines for what's normal and what's not. In general, an E to E prime of less than eight is generally normal, not low, but normal. And an E to E prime that's greater than 15 suggests that you have higher feeling pressures. And a good little clue here is that the E to E prime plus four is a sense of your left atrial pressure and or your wedge pressure. So you can use that again to guide perhaps either diuresis or to avoid giving additional volume if needed. And again, E to E prime here is used to help us estimate those left atrial pressures. The numbers to remember is that less than eight means that likely you have a low or normal wedge pressure. I take it back, not low, but normal wedge pressure. And those patients, perhaps diuresis is not best for them though we may do it in clinical practice, but ongoing diuresis may not be best. And those with high E to E prime suggest that they have higher wedge pressures. And those patients without optimization and diuresis on the ventilator may struggle with ventilator liberation. There's some data here suggesting the sensitivity and specificities of those numbers in mechanically ventilated and critically ill patients. So putting this all together, you can use this ABCDE approach when thinking about using ultrasound to optimize lung mechanics and guide diuresis, looking at aeration and the lung itself, looking below the diaphragm, ascites and other contributors to high pleural pressures, looking at the lung itself, specifically diastolic dysfunction, thinking about the diaphragm and those supporting infrastructure. And then of course, thinking about extra diaphragmatic muscle and how they may affect your ability to optimize your lungs. So hopefully I've been able to convince you that in some cases lung ultrasound is excellent or ultrasound in general is excellent for evaluation of mechanical ventilation. In some situations it can be useful and then in some situations perhaps the jury's not fully out yet. Thank you so much for your time.

point-of-care ultrasound

mechanical ventilation

diuresis

acute respiratory failure

lung evaluation

diaphragm assessment