I'd like to welcome everyone to our session on case-based ventilator graphics and using graphics, if not to optimize patient management, at least improve it somewhat. And I'm real pleased to chair this panel, Dr. Natalie Yip, Dr. Brady Scott, and Dr. David Vines. And we'll let them have their titles up there and we'll continue on. We're gonna try to keep this reasonably quick. We've got four presentations with a fair body of data and holding questions till the end, but we will be happy to answer questions at the end, even if we run a little bit over, though you're probably anxious to get outside. So I don't have any disclosures and go ahead and please evaluate sessions because if we don't get evaluated, we don't know what's good, what's bad. And I'm gonna talk about basic mechanics in resolving the high pressure alarm with a focus initially on basic mechanics. Why did I? Slow, they're just slow. So the waveforms move slow. So we have a case, no history, no trends for the ventilator. Therapist tells you that the peak airway pressure has been going up over the past hour. Based upon the ventilator graphics alone, which one of the following is most likely? And this is not an ARS question. We're gonna get to the same thing with an ARS question in just a second because I'm gonna answer this for you. Okay, go ahead and answer it. We have this as an ARS, I'm not sure why. Go ahead and answer. Okay, you have to click the arrow down and then the video will play. So when the slide comes up, click one more time. Only four votes have been, okay, here we go. You went too fast, you clicked twice. OK, a plateau here. So 30 votes and worsening asthma. And I'm glad to see that because I think the right answer is either A or B. And I'd like to show you why I think that's the right answer. So we have either A or B. But if you'll note, and we'll talk about this, either A or B because both compliance and resistance are abnormal. You don't have a history. And so you have a low compliance because your plateau pressure minus peak is fairly high. And your peak plateau difference is also fairly high. So both are abnormal. And so if both are abnormal, you can't differentiate pulmonary edema with a loss of compliance from bronchospasm with increased resistance. You just know both are present. But without a history, you don't know is this someone with bronchospasm acutely on top of their pulmonary edema or is something else going on. So when we talk about the mechanics of ventilation, to drive air into the lungs, you need to overcome two primary forces, the resistive forces of your airways and the elastic forces, commonly compliance or elastance, of the lung and chest wall. And it is worthwhile to understand how to calculate compliance and also resistance. And hopefully by the end of this, you will understand why I think it's important and what's normal. So a normal lung compliance is 80 to 100 cc's per centimeter of water. What does that mean? It means that's my tidal volume over my driving pressure, which is the plateau pressure minus P. It also means that pressure support of five is a ventilating mode in normal lungs. Because with the pressure support of five, with a normal lung compliance, you're going to get tidal volumes of 400 to 500 cc's. And I think people forget about that. Oh, they're only on five of pressure support. OK, yeah, but if you're quadriplegic from a high C spine injury, take them off five of pressure support. They may hypoventilate and crash. So remember that. And resistance is the peak pressure minus the plateau pressure over the flow rate. And normal resistance in an uninhibited individual is two centimeters of water per liter per second. If I put an endotracheal tube down you, the normal goes, and with a circuit, goes up four or five fold. Why? Well, an endotracheal tube is a darn bit smaller than your trachea. Has to be or it won't fit. We need a balloon to seal it. And resistance is proportional to the radius to the fourth or fifth power, depending upon whether you've got laminar or turbulent flow. And how do you get these values? You need to have a square wave on your flow pattern so that you get a constant flow that allows you to calculate resistance. You'll see the abrupt rise to your peak pressure, a then gradual fall to a plateau if you have an inspiratory pause, and then the deceleration during exhalation. And this is the typical square wave flow pressure waveform pattern that you will see on almost all of your ventilators. Maybe consider using the laser pointer for that. Do what? The laser pointer on the power point? On the power point so they can see it on both screens. Does that work? I don't see it over here. Show me. It's because of that grip. It's over there. It's hard to see that light. Now it's there. Hot dang. Thank you. And remember, and the reason we want a square wave and a pause is that if you don't have a setting where you have at least one point of zero flow, you're going to have a pressure gradient in one direction or the other. On inspiration, your pressure gradient is going to be from the circuit down to the alveolus. So your circuit pressure during inspiration will always be higher than the actual alveolar pressure until you get to no flow right here, where you have equilibration of your alveolar and circuit pressure. Conversely, during exhalation, the pressure gradient's in the other direction, from the alveolus out to the circuit. Because if it didn't have that, you couldn't exhale. So the only time that your circuit pressure reading is the same as your alveolar pressure reading is when you don't have any flow. And you can see that on your flow signal that it goes down to zero. So case one, this is not with ARS. So why is it A or B? Well, first of all, I have my peak pressure and my plateau pressure, which I kindly put on the actual digital display for you. And I have a zero flow at the end of inspiration, which is why I have a plateau pressure. And so my peak pressure and my plateau pressure difference is 17, my flow, and my therapists get mad at me. I routinely have patients on a constant flow at 60 liters per minute. Why constant flow at 60 liters per minute? How many liters per second is that? One. And I can usually divide by one and get the right answer. Not always, but usually. And so I have a flow of one liter per second, a peak plateau difference of 17. So my resistance is 17. And is that above 10? So it's abnormally high. My compliance is my volume, which is exhale volume of 350, and a plateau pressure minus peak. My plateau pressure is 25. My peak over there is 5. So it's 20 divided by 350. And actually, it's 400. So I've tried to make it easier. 20 divided by 400 is, or 400 divided by 20. Thank you. Is what? 20. 20. Is that less than 80? Yes. So I have abnormal compliance and abnormal resistance. And that's why I couldn't differentiate between something that was causing a problem with lung elasticity versus lung resistance. Both are abnormal. Pressure waveform, constant versus decelerating waveform. Just because you have a decelerating waveform does not mean that you cannot calculate compliance. But you have to be sure that on my decelerating waveform, if I'm going to calculate compliance, that I do have a point of no flow. I cannot calculate resistance because my flow rate is continuously varying during inspiration. So I can't calculate resistance with a decelerating waveform. And that's why I use a square waveform if I'm in a flow And that's why I use a square waveform if I'm interested in lung mechanics. So this patient is in predictor regulated volume control, PRVC, auto flow, VC plus, whatever you want to call it. And you can also see it in pressure control with relatively short eye times. What happens is I have the end of inspiration, but I still have flow. So whatever plateau pressure the ventilator you think you have isn't a true plateau pressure looking at the graphics because you haven't done an expiratory hold. You need to go to zero flow. So the high pressure alarm. High pressure alarm is sounding. Therapist calls you. What's wrong? What should you do? And I think this is my approach to the high pressure alarm. Others may have different ones. And you can ask them if they think I'm nuts. But what I do is I take the high pressure alarm threshold and turn it all the way up, 100, whatever is the highest. I want to get rid of the high pressure alarm for two reasons. One, it will allow me to decide what's going on. And two, what happens to the patient's minute ventilation when the high pressure alarm goes off? What happens to their tidal volume? Goes down because what happens when the high pressure alarm goes off? It opens the exhalation valve and dumps whatever else of the inspiration you got left. So your tidal volumes will be low every single time that high pressure alarm goes off. And if it happens over the course of a minute or two, you're going to be underventilating that patient, or at least ventilating them less than you were before, potentially with adverse consequences. So I turn the high pressure alarm alarm level as high as it will go so I can see what's going on. And then I will switch them to a constant flow setting so that I can then measure along mechanics and ensure that there is a point of zero flow on inspiration and exhalation. And then I can measure my mechanics. And then I can assess what the heck's going on. Why did the pressure alarm go off? Was it resistance? Was it compliance? Was it potentially both? And then what does that change my differential? And then how do I approach this for my patient? Obviously, a kinked ET tube could do that, but it allows me to do whatever I need to do. And actually, my first thing to do after I get rid of the high pressure alarm is to pass a suction catheter to be sure that the tube is not kinked or that there's not an obstruction to the endotracheal tube. That's fairly common. So interpret these changes. This is ARS. Which of the following is true? On admission and then four hours later, you've got a second set of values. All the ventilator values are exactly the same. Same tidal volume and same settings, just the graphics have changed. No, they can't see what they're trying to do at the same time. Yeah. That's true. A lot more active votes. Oh, shoot. It's OK. Oh, dear. So many votes. We broke the system. You don't know what the results are? I probably blew it, because hopefully, people got static resistance has increased. And so why has that, if you look at the peak pressure, plateau pressure, peak pressure, plateau pressure here, then later, the peak pressure, plateau pressure has changed. The peak is lower. Plateau is the same. So my resistance has decreased. Now, has my plateau changed? No, my plateau has changed the same. My tidal volume is the same, and my peak is the same. So my compliance hasn't changed. So hopefully, you can understand why simple flow time, pressure time scalers can help you decide what might be going on with your patient at a given time, and at least give you clues as to what treatment options you might want to deal with. Thank you. Hey, everybody. Thanks for coming. Are you excited? Woo! It's 3 o'clock. I just figured we'd pump this up a little bit, because we're very grateful that you're here. It's the end of the day. I know there's a lot of Hawaiian sun out there. So we actually are really grateful that you guys are as excited about ventilators as we are, and that you're here to join us. So my portion is about titrating PEEP, an ARDS. So I'm going to talk a little bit about titrating PEEP. My portion is about titrating PEEP, an ARDS. I don't know about you guys. We face this constantly. So hopefully, we're going to get to go over some tips, how to interpret waveforms, ways to get feedback on what you can do with titrating PEEP. So I'm from Columbia in New York, where I'm the section chief of critical care there. And I have no disclosures. In case you haven't done this already, please scan this QR code to interact. So to start off, just briefly talking about the risks and benefits of PEEP. So utilizing PEEP, on the left-hand side, is a purported list of benefits. So we try to mitigate ventilator-induced lung injury by recruitment of collapsed lung areas. That can potentially reduce intrapulmonary shunts. It can prevent cyclic lung opening and closing. It can reduce tidal lung stress and strain, and then improving lung compliance, and then promote more homogeneous ventilation, and then ultimately improve oxygenation. Although one caveat about oxygenation is that doesn't necessarily pertain better patient-centered outcomes. On the risk side, when you have PEEP above a certain threshold, it can reduce cardiac output by diminishing your venous return, increasing your pulmonary vascular resistance. You can also cause ventilator-induced lung injury if you have failure to recruit lung. So then you have overdistension and lung stress in certain areas of your lung. Additionally, you can get increased alveolar dead space. So how do we choose the right amount of PEEP? Over the years, there have been multiple suggested approaches, the most simple being tables. So we have these PEEP and FiO2 tables, and then the other ways of doing it is to actually look at the physiology. So most of us would agree our patients are not one-size-fits-all. There's been a lot of attractiveness looking towards individualizing PEEP choices based on the patient. So you can use open lung ventilatory strategies, looking at pressure-volume curves. You can try to estimate the transpulmonary pressure to really understand what the transpulmonary pressures are. And then you can utilize driving pressure and stress index, which are two things I'm going to try to go over today. Just a brief thing about PEEP tables. I don't want to undermine this. I still think that there's a role for this, especially in areas where you don't necessarily have a lot of other things to grab for, and it's also a starting place. There have been multiple RCTs that have different variations of PEEP tables. There is one meta-analysis that did combine the data across multiple trials, and that did show that a higher PEEP strategy tends to portend a benefit in mortality. Just so you guys have a sense, the high PEEP average is somewhere around 15, compared to 9 is the way they compare it. We're going to go through some techniques by utilizing a case. Case number one is a 57-year-old woman with COVID ARDS. I'm sure everyone has dealt with this. The patient has refractory hypoxemic respiratory failure, is paralyzed, prone to nonpressures. The tidal volume is set at 5 cc per kilo of predicted body weight. The rate is 30, FiO2 is 90%, and PEEP is 12. The ABG is 7, 2, 2, 68, 58, with a peak spray pressure of 41, plateau of 32. With this, what would be a reasonable next step? A, increase the PEEP. B, decrease the tidal volume. C, decrease the PEEP. Or D, no change. Think about your letter, because when I flip to the next slide, you're not going to be able to see the graphic. Everybody have their letter? I'm going to flip. So go ahead and choose the letter. I should sing a little Jeopardy music or something to fill the time, right? Do a little jig, do a little dance. Okay, so we have about 50 votes. So let's see what you guys thought. All right, so nice spread. So this is good. That means we have a good discussion here. But many of you said increase PEEP. So I'm going to go over what we were actually thinking about here. So this is a discussion about stress index. Have you guys heard about stress index? How many have heard of it? Okay. How many use it? All right, okay. So basically a stress index is the definition of a stress index is that when you have a constant inspiratory flow, square waveform, the shape of the airway pressure time relationship reflects changes in the respiratory system compliance during inspiration. So the stress index specifically is the rate of change in the slope of the pressure time curve during tidal inspiration. So in the middle here I depict a stress index of one. This is where the slope remains constant, meaning the respiratory system compliance remains the same throughout the tidal breath. This corresponds to the straight portion of the inspiratory limb of the pressure volume curve. On the left is a stress index of less than one, whereby towards the end of inspiration there is a flattening of the curve downward, indicating that there's a recruitment occurring during inspiration. This corresponds to the lower inflection point in the inspiratory limb of the pressure volume curve, and this may indicate a role for more PEEP, right? Because you're spending some of that breath to recruit lung. On the right is a stress index of greater than one, whereby towards the end of inspiration there's a sharp rise in the slope of the curve, indicating overdistension. And this corresponds to the upper inflection point of the pressure volume curve, and this may indicate the need to reduce your tidal volume or reduce your PEEP. Hopefully this demystifies a little bit of your stress index. So note in the last point that I just said about a stress index greater than one, that you can adjust the PEEP or adjust the tidal volume. The point is that optimal PEEP based on stress index is dependent on the tidal volume. So this just happens to be a plot of one patient's compliance based on differing PEEP and tidal volume. And clearly you can tell that the best PEEP really varies on what tidal volume you're choosing. So going back, oh sorry, this is just a screenshot of different types of vent waveforms showing a stress index of one, a stress index less than one, and a stress index of greater than one. I'm going to take my laser pointer. So this is equals one. Hopefully you can see it is blown up. The idea is that this here is a straightaway. The stress index of less than one, you can see here that it curves, right? And then over here with the stress index of greater than one, you can see how it just shoots up at the end of inhalation. So the key though, in order to do this, is you do need to have a little bit of a slower flow and a constant flow. Okay? So a lot of us use decelerating flow waveforms for volume control. You won't really be able to utilize the stress index in that situation. So you do need a constant flow. And so in the case that I presented, it was actually this waveform that showed the stress index of greater than one. That's why the answer was to potentially decrease the tidal volume or decrease the PEEP. Okay? All right. We're going to move to the second case. And the tidal volume was already low and they were hypercarbic. Yes, yes. Sorry, do you want to say that a little louder? And the tidal volume was already low at five and the patient was hypercarbic. Hypercarbia ought to alert you to the potential for over PEEPing. So case number two, we have a 40-year-old obese man, so a BMI of 45 with aspiration pneumonia and ARDS, intubated, paralyzed, and proned. Tidal volume, again, is five cc's per kilo, predicted body weight, respiratory rate of 30, FiO2 is at 100% and the PEEP is at 14. The ABG is 73360, PiO2 of 58 with a plateau pressure of 30. At this point, the PEEP is increased to 18 and the plateau pressure is 32. So the question is, what would be a reasonable next step based on the information I gave you? Is it A, increase the PEEP to 20 and then check another plateau pressure? B, decrease the tidal volume to four cc's per kilo? C, decrease the PEEP back down to 14? Or D, no change? Remember your letter, and I'm going to flip to the next page. Nice. I've got 37 votes. I'm trying to see if I can at least get up to 50. Let's see. All right, so many said no change. A few of you guys said an increase in PEEP. Okay, so looks like this is another opportunity for me to have you guys understand where I'm coming from. So this is a case about driving pressure. So traditionally, we've been sizing tidal volume in relation to a patient's predicted body weight, right? So we know that from the ARDSNet ARMA trial, tidal volume in cc's per kilo. But now, I'm sure you guys have heard about the concept of a baby lung, right? That ARDS is a heterogeneous process. There are varying degrees of ventilable volume, and that can be approximated by their respiratory system compliance. So rather than indexing tidal volume by predicted body weight, it would seem physiologically sound to index tidal volume to respiratory system compliance. So driving pressure is the difference of taking plateau pressure minus the PEEP. So you can do a little simple formula manipulation here and basically show that essentially driving pressure is a measure of lung strain. So ultimately, by doing this, using driving pressure, this may help us understand the size of your tidal volume in relation to the patient's ventilable volume, and it also accounts for that heterogeneity of ARDS in patients and their lungs. So how do you apply driving pressure in practice? So what I tend to do is we'll give a trial. Go up on your PEEP. And when you increase your PEEP, your plateau pressure increases by less than your change in the PEEP. That means that your driving pressure has decreased, right, after you went up on that PEEP, and that may represent lung recruitment. On the flip side, if you go up on your PEEP and your plateau increases by more than your change in PEEP, that means your driving pressure has increased, and that means that you may have reached a point of hyperinflation. So what's really attractive about this is that it doesn't require any special equipment, right? You're just at the bedside playing with your PEEP. The one thing is that the patient has to be passive, as you know, when you measure plateau pressures. And there has been some large observational studies that have shown an increase in mortality for patients with higher driving pressures in the range of greater than 13 to 15, and that is independent of just a straight plateau pressure or tidal volume. To date, still not a prospective study yet supporting its use, but at this point, right, using physiology, this is why I love critical care, using your knowledge of physiology and pathophysiology to try to individualize your treatment. So going back to the case that I presented, right, we had a patient who was already on 100% of 502, tidal volumes of 5 cc per kilo, PEEP was 14, plateau was 30, and so the driving pressure initially was 16. Subsequent, we went up to PEEP of 18, plateau pressure was 32, so the driving pressure after going up on the PEEP was 14. So in that situation, it looked like we might have recruited some lung. So the next step, the question is, what would you do next? So many said no change. I don't think that's necessarily wrong. My preference would have been to go further, to go up again, thinking that potentially I could have recruited lung. And I know some might say, well, your plateau pressure is already at 32. Aren't you a little worried about that? And what I would say to that is the patient's obese, right? So we know that a plateau pressure of 30 is kind of, again, one of those one-size-fit-all, right? Maybe that's where we stop. But there have been multiple post hoc analyses of the different trials that we've had in the past that really show that actually the patients who are obese could actually benefit from even higher PEEP. So I don't know that I would stop at 30 for a patient like this. In fact, at least in my own clinical practice, this is where I might utilize an esophageal pressure balloon, something like that, to give me a little bit more bravery to go up on the PEEP, because I don't know that we should necessarily stop at a plateau pressure of 30, because likely the transpulmonary pressure is not at a dangerous range yet. So last bit is that, you know, we started in the beginning, right, with two of our important variables for lung injury. There's tidal volume, there's PEEP. Next, we added driving pressure as something to think about, as something physiologically sound, as a marker of strain on the lung. There have been several others that have been proposed as contributing to this, which have been lumped together in one term called mechanical power. I'm not going to overwhelm you guys. I've got a little overwhelmed just by looking at this formula. But suffice it to say, there's a lot of different variables that really contribute to this. But of note, I would highlight one variable, which is respiratory rate. So there have been some studies that actually show that respiratory rate, in addition to driving pressure, tidal volume, PEEP, has an independent association with the risk of death, but to a much lower degree than driving pressure. But there's a tradeoff, obviously. So there's still a lot more work needed to be done to better understand how to titrate all these different variables to optimize how you deliver mechanical ventilation. So to summarize, mechanical ventilation is injurious to the lungs. We know that. And ventilator-induced lung injury is largely driven by overdistension of certain regions and adelaide trauma of others. So it's attractive to try to come up with that right PEEP, right, to really optimize how we're ventilating the lungs. Patients with ARDS are heterogeneous. So this one-size-fits-all idea really probably isn't the best approach. It's difficult to assess the balance of recruitment and overdistension, and it's really hard to determine what's the right PEEP tidal volume. But hopefully, just by thinking about driving pressure, stress index, these have physiologic bases and are relatively easy to use at the bedside. But the biggest caveat, there are no prospective studies that show that that approach leads to better outcomes. So thanks for listening. Thank you to everybody for being here. Again, I just want to say what Dr. Yip said. I think we all realize that I believe we are between you and Hawaii. So thanks for being here and geeking out with us the way we like to geek out. For any early career folks that would maybe one day be on stage teaching, what you don't do is you follow somebody like Dr. Yip, who has amazing slides, and I was sitting over there like, how does she get the bag on the slides and put the stuff in there? Like, I don't even know how you do that. So I don't like following people like Dr. Yip because I have nowhere to go but down from here. So my name is Brady Scott. I am a respiratory therapist. I'm an associate professor at Rush University in Chicago. So we're going to talk about here intrinsic PEEP, circuit leaks, and a failure to deliver set tidal volumes. So my disclosures have nothing to do with what I'm about to talk about. It's some research funding, and I contribute to Reliance Media. And we have this already, so we're going to move forward. So I'm going to throw up a slide and say, so we're just going to jump right in and say, while rounding on patients, you note these graphics. And I'm going to give you no other information. Just based on the scalars alone, which of the following is most likely occurring? And like my colleagues, I'm going to give you a second to look close, and then I'm going to ask you to get your letter ready, then I'm gonna take you to the next slide, so no other information, so just look at your scalar graphics. All right, and here we go. All right, we are on the mark. I did not have the Jeopardy music. I think we can only do that one time, we're gonna get caught for copyright problems there, right? All right, just for the sake of time, and we have, all right, look at that, that's awesome. All right, so let's see if we got it right. So I click one time, and all right, intrinsic peep, great. So some folks said some psycho-asynchrony, so cycling's what's turning the breath off. You know, auto-cycling, where you've got a lot of breaths happening. Intrinsic peep, or flow-asynchrony. So let's go talk about it, let's see what it is. So what we probably most likely have, oh, what happened here? I don't know why that hit, is there, we're gonna move on, whoop. So in reality, what we were seeing, I'm gonna try to go back, I'm just trying to get through this, is indeed you're right about the intrinsic peep, all right? So some of you are probably looking here, let me get my little pointer. We were looking at this flow time scaler, looking at the flow time scaler here, and you can see that on the expiratory flow it's not reaching baseline, is there a problem? Too loud, can you hear me? Yes. Okay, sorry if I'm too loud. I apologize, that's been a lifelong problem of mine. All right, so we're looking at this, and we can see that the flow, the expiratory flow graphic is not coming back to zero, which would imply that we might have some intrinsic peep. So the question here, and ignore this, this is just something that's coming on from the ARS, but intrinsic peep, so we know the consequences of intrinsic peep, is indeed it may increase inspiratory pressures, which Dr. Yip and others have already talked about, this could actually cause a problem with a ventilator-induced lung injury, and there could be some cardiovascular side effects, similar to if you just turn up peep yourself, right? So if you're turning up peep because you went in pre-vaccination, we know that we worry about blood pressure changes and those type of things because of decreased immunity return, and ultimately on its effect on cardiac output. So I think most importantly, we think about intrinsic peep as how do we mitigate it? How do we deal with it? So again, you were looking at the flow time scaler, you could see that the patient was simply exhaling, and before they got all the breath out the baseline, which would imply there's, again, I think Dr. Bowden really said this nicely, what you see there was a, there's not equilibration between the patient and the ventilator, effectively, right? The patient's still exhaling, still has room to go, but we give a breath, so we're trapping that gas, and it's a little extra peep that we don't wanna give, so how do we mitigate that, how do we treat it? Well, we have mechanical ventilation settings first, right, although there's really not an order here, but that's what my slide there is, I guess, and we think about decreasing respiratory rate, and I'm gonna show you some images, so we can turn down the rate, you can decrease the patient's tidal volume, or you can increase expiratory time, increase expiratory time, or another way of saying that is decrease your inspiratory time, and we're gonna talk about those now. You could also try to do what you can do to reduce resistance to flow, and so my colleague here, Dr. Bowden, when he said, you know, resistance, airway resistance is high, how do I go about mitigating it? I agree with him, I said it wasn't crazy at all, as a matter of fact, one of the very first things I do as an RT is I look at the patient to see if they're biting the tube, especially in a pretty, it was a pretty extreme example of your peak pressure there, or looking at the, you know, maybe there's a lot of secretions, or perhaps there's a biofilm buildup inside the tube, and the interluminal diameter has actually decreased, so all those things can happen, so maybe we can just simply treat it, right? And, you know, and sometimes albuterol and atrobin or ipertropion bromide, this is what we need, we're actually having a bronchospasm issue, so let's go look. So let's look like we're gonna decrease the respiratory rate, so let's get our eyes trained on this, this is a screen that we have here, that we've been showing so far, so hopefully by now you've seen that these are our settings here, this is kind of like what you set, and this is what you get on this ventilator, so on the x-axis here, what you set, so we have a rate of 24, and on this next panel, you see what I've done here is we've decreased the rate to 16, and what has that done? So what that has done, you can see that if you just simply look at like, let's say one of you, or some of you, those of you that are just not very familiar with vent graphics, you can see that literally the distance between the beginning of this breath, beginning of that breath, has changed, right? Which means that the size, the inspiratory time on this breath is the same, but the expiratory time is different, and let me show you what I did to create this. I created that little fancy box, not near as good as Dr. Yip does, I tried, I have graphic envy a little bit up here, but you can see what I did was I created this little yellow box that demonstrated the size, you know, basically the length that exists on the expiratory time in this side, and I copied and pasted it, and I put it on the other side. Right? So you can see that I've added this much more time to allow the patient to exhale. So that has changed the total cycle time, as the eye time stayed the same, the inspiratory time itself stayed the same, but the expiratory time was lengthened, right? So decreasing the rate as a way to mitigate, and if you look at the graphic, you can see I get closer, coming all the way back to zero. The next is decreasing tidal volume. So here again in liters, you have .48, and in this neighbor, you can see we've decreased it to .32, the respiratory rate is the same, everything else is effectively the same, except for the volume is less, and there you go, so .32, that's why it's 300 cc tidal volume, and if you look across the line, it is a line that runs exactly across the screen, so you can see that the tidal volume itself has lessened, and you have mitigated some of the amount of air trapping that occurs, you can see that your flow time scaler on this side is closer to coming back to zero, which has minimized the amount of air trapping. And the next version here is increasing the expiratory time here, and we did this simply by increasing the flow rate, which I feel like I don't know why I even said this, increasing expiratory time, I feel like it's backwards, because what we did is we decreased the expiratory time, which again effectively increases expiratory time. So what was the consequence of that? I know that Dr. Bynes and I, we teach the same students, and something I always say is every vent setting, every time you make a change on a ventilator, there's a purpose, but there's a consequence, potentially, right? So we go back and we look, here you can see that the flow rate has indeed increased, right, and then your flow time scaler, you have increased, it's changed, but what else changed? Your peak pressure went with it significantly, right? But again, your effort, if that was the case, to actually try to mitigate your air trapping, then perhaps that's what you've wanted to do based on the clinical situation you're in. And then finally, reducing resistance to flow. So this is, as a respiratory therapist, this is when I love when you order the bronchodilators, right, so resistance to flow here, and what you see, the big difference here is that the peak pressure has decreased because we've done something to reduce resistance, whether it's the suctioning the patient, perhaps giving the bronchodilators, and what another thing I point out here, making sure I'm looking at the same thing you are, is that the slope of the actual expiratory time, the peak expiratory flow slope, is actually quicker to baseline. So you don't have so much of an airflow limitation because you've reversed it. It's pretty neat when you're at the bedside and you're an RT like me, and you're giving bronchodilators to somebody with bronchospasm, and you look and you can see how that changes its slope versus looking like this before. All right, so let's move on. So we can get back, I'm just gonna make sure we're on track, we good on time? Okay. Three minutes. I gotta hurry. All right, so what do you see here? Case one continued, I'm gonna give you no patient information. Your epic's down. All of your charting's gone. You just have just the patient stuff, right? What do you see? And I know for some of you this may be very obvious, but you know, for those in the room that this, you're relatively novice, this may be a little tricky. So A, is it a leak? Is it a more intrinsic peak? Flow asynchrony or breath stacking? All right, so here we go, A, B, C, or D? Number's going up quickly. That's good, I like that. It's Mission Impossible, huh? Yeah. All right, let's go look at it. We have 50 votes in. So what do we see? Correct, circuit leaks. So for those of you who are like, what? I thought that was, flow is synced, let's go look at it. All right, so what we have here is a circuit leak. And this is my favorite one, this is the one that I've been using for a long time. And it's a circuit leak. And this is my favorite one, this is the one, you know, a lot of times, of course, clinically you can hear it. But as I teach sometimes, is when you're looking at the volume time scaler, graphic. So this is volume on the y-axis, time on the x-axis. Effectively, what goes in should come out. What goes in should come out. And if it's bent kind of over like this, this is saying that the expiratory side, the other side of the ventilator is not seeing the volume come back. All right, so you have a leak. So let's go take a look at it. Sorry, I don't know what I did wrong in the ARS, so I apologize on that. So let's look. So what we're looking at is here. So again, you're looking right there, and this blue line should be coming down to baseline. Baseline, if 480 went in, 480 should go out. You can see this in other place. There's my 480 set. My expiratory tidal volume is 370. But I can graphically see it, and I can numerically see it on these modern mechanical ventilators. And so here, again, this should be what this looks like. Of course, not yellow. This is just me illustrating it. Up is the volume. Down here, some people will say, hey, if you got a check mark, if you got a check mark sign on your volume time scaler, the check mark is how you know you have a leak. But again, I think it's even easier to say, if this much goes in, this much should be coming out, right? That's what should happen. And in this case, again, your 480 versus 370, where I've circled those on your tidal volume set versus your exhaled tidal volume, all right? So what I did here in this case to improve this, I didn't get rid of the leak. I improved the leak. It's a little better. So there again, you can see that that still represents some leak. We went 480 to 370 a minute ago. Now we're 480 to 420. But you can still see, there's still a bit of a leak in this circuit, right? So you improved it, you just didn't get rid of it, and that's how you're seeing it there, but between those two numbers. So again, numerically, you can see this, and in like a graphics package in this ventilator, you can literally kind of blow it up and look at it closely, and it would be the same exact amount of leak you would see there if you want to fix it. And then we'll wrap up here real quick. For those that use modes like PRVC, you see things like things like say volume limit, tidal volume not achieved, those type of things. Sometimes there are settings you have to go look at. So volume limit in this ventilator, so what we've asked the ventilator to do is give a tidal volume of 480, but you actually have maybe have created a situation in a ventilator that you've actually kind of capped it off. It was very similar to the peak infiltratory alarm a minute ago. So again, for those of you that are in the PRVC world and those type of things, make sure that you actually are allowing the ventilator to follow your instructions, what that may mean on the ventilator that you're on. So in this case, I have a tidal volume of 480, but then I raised the ceiling to let my ventilator function the way that it should. All right? So conclusion, scalar graphics can help identify intrinsic PEEP, which is auto PEEP air trapping and circuit leaks, and be aware of how limit settings may impact your mechanical noise. And thank you very much, and we will continue. Well, those were a great series of lectures. The only problem following those three is that I have about 10 minutes left to present. No surprise there, but hopefully that was educational for you, and today I get the opportunity to talk to you about dyssynchrony and how to mitigate it. My name is David Vines, I'm a chairperson for the Department of Cardiopulmonary Sciences and the Associate Dean for Clinical Integration at Rush. Dr. Scott and I work together on a daily basis. So we're gonna, I guess my, I guess, good thing. My disclosure is all research funding, none related to this topic, and please evaluate. There's our objectives, let's move on here. So these are types of dyssynchrony, and I use this 2011 article just to try to give you some reference of common language. So one of the problem in recognizing dyssynchrony is depending on who you read or who you follow, sometimes there's multiple names to refer to the exactly the same thing. So I tend to try to stick with this publication and this definition for that reason, and they have really nice examples in this article. So after this presentation, if you wanna go pull it and read it, this is a great resource for you that was published in Registry Care. So the ones with the stars we're gonna actually talk about in this lecture. Delay triggering is about an abnormal gas flow in the beginning, or a delay rise in gas flow for some reason, abnormal settings around rise times, things like that that we're not gonna talk about today. But auto-triggering is just repetitively triggering of a breath, and then auto-peep, or intrinsic peep, or air trapping, Dr. Scott just covered very well with you. And so we're gonna talk about some of these others on the scale here. So let me grab this pointer. And so here's a trigger, Dyssynchrony, and so if we, some people refer to this as mis-triggering. So if you have a mis-trigger, the patient makes an effort and the vent doesn't trigger for whatever reason, either the sensitivity is set to a point where they cannot reach the set value to trigger the ventilator, or there's air trapping perhaps that is causing them to need to pull more effort to be able to trigger the breath. Another example of some common ones would be breath stacking, or double triggering of the breath, and that is where the patient's neural time is usually, or effort, is greater than the total volume set, one or the other. Either the eye time's too short on the ventilator and their neural time is longer, or you have too low a total volume set. And they actually pull into when the vent thinks it's gonna cycle into expiration, and they generate enough effort that they actually trigger a second breath. So essentially they are doubling the amount of total volume you give. So if you even had five ml set, you just gave them 10. So we really want to try to avoid that situation. The premature cycle is one that's a similar problem, but this is one where it's all around the neural time of the patient is longer than the eye time you have set, and the patient is actually breathing into the expiration. They just are not generating enough effort to cause it to double cycle. It's like a warning sign. Hey, I have a premature cycle. They generate a little more effort, and they will potentially begin breath stacking on you, or double triggering at that point. Another one is an active exhalation, or a delay cycle, where at the end of the breath, the patient actually exhales, to very common in pressure sport, used to be a major problem in using pressure sport in obstructive lung disease, which has really been clear, or helped by the ability for us to set this expiratory trigger sensitivity, or percent expiratory peak flow cycle, so that we can actually start to control when the breath ends in a spontaneous one, which is demonstrated here in this other slide. So if we choose to change the percentage from 25 to what looks to be 60%, 60% there, then the breath will end faster in a spontaneous breath, so you're actually giving them a little more expiratory time in that process, and as you can see in this first part of the slide, which I like to do when I walk into a patient's room that's on a mechanical ventilator, is I'm saying hello if they're awake, I am looking at their abdomen to see, one, that they are actually making an effort to breathe in, I see their diaphragm move, two, they're actually not recruiting expiratory muscles to force the vent into cycling. If I see them using their abdominal muscles to force an exhalation, I already know what I'm looking for before I ever get to the ventilator. And so it's just a habit I get in as I walk into the room, see the monitor, vital signs, then look at the patient as I can hear the ventilator trigger and cycle. The other one that's fairly common is flow desynchronies, and so a very common pattern in flow desynchronies where you see this arrow is the scooping, where you see the patient making an effort. Realize in volume control, this is the problem in that mode, because these two waveforms can't change. You set them, you set the flow pattern, you set the amount of flow, you set the inspiratory tidal volume. So those flow patterns generally don't change in volume control. The only flow pattern that can change there will be a pressure waveforms when you're looking at them. The other one that we don't rarely think about using in this case, that's probably older than I am when it was published, is the fact that these figure eights in a pressure-volume curve. So if you look at figure eights and you turn this on, and you see this curve, I put up a pressure-volume curve, we think about them in setting P, and those are really slow flow pressure-volume curves, and usually patients are passive if you were gonna measure with those or use those. In this, a dynamic pressure-volume curve will actually tell you when the patient exceeds the flow, it's essentially this waveform where you're showing them pulling in on an effort, and then they stop at this point. Breath finishes, they cycle. So we have a quick case here that we're gonna run through for you in the next five minutes, hopefully, where we have a 38-year-old ARDS patient, you can see 80 kilograms, and we have them set up there at six mLs per kilogram, and they have been weaned down to 60% oxygen with a decelerating flow pattern in there. So this is our first waveform that we're looking at, and it's gonna move a little slower than I like, so we're about 30 minutes into initiation of them, and as Dr. Scott pointed out, we have a very small leak in the system that is there, but. Hopefully, everybody can see that now. Yes, so here's our question. So from this question, think about the types of the synchrony, so I just ran through real quickly for you those, so tell me which one you see. So I'll let you think about your letter, A, B, C, or D, before I click to the ARS. We ready? Okay. A few people are not sure, coming in, very good, so we will spend very little time here other than talking about how we want to potentially fix this. So one possible correction is that we can increase the flow, let's see if it will move, so we turn up the flow to try to fix that problem. And you can see we still need probably just a little bit more flow, one of the problems here is the eye time got really, really short, so may or may not, we can discuss that whether you would add a pause or not, wherever you are comfortable with, with eye time there in that process, but even here we would need more flow on that waveform. Another possible correction is switch to a pressure limited mode. So the beauty of a pressure limited mode is the flow is variable, the more flow the patient asks for, the more they get, the less they want, the less they get, and the issue is now though you have to chase tidal volume because the only waveform in this point that becomes constant is that square pressure waveform, if rise time is set appropriately it will be square. And so at this point you can see as Dr. Bolton had pointed out, flow is going to zero in this patient here, and they're actually probably tolerating a little longer inspiratory time than they would be otherwise as the waveform actually starts to move now, all right. So the next morning we find this waveform. So I'll give you a second to look at it, questions coming. Looks like what, every third or fourth breath there, that little blip, okay. So what are we seeing here? What type of desynchrony are we seeing on the screen? We got a number A, B, C, D, our letter, ready, awesome, you're ready to go to the beach. Okay, very good. Triggered the synchrony. So here I want you to note from earlier you can see that this is most likely has a little bit of air trapping. It looks like our leak has gotten better, but as Dr. Scott pointed out, that check mark's clearly obvious now, more than it was before. And then occasionally you see this mis-trigger. If you look, you see a decompression breath. They're actually exhaling more volume than they had in end because they didn't turn the vent on. So they're just pulling against a, whatever gas was in the circuit around, whatever they could pull out of the peep. So if we look at this point now, they have a little more volume as they exhale than what we delivered, but that would be where you would see them have decompression of them. And so one of the fixes here is to potentially increase the flow. At that point, again, we're gonna run to a shorter inspiratory time where you become comfortable with, but at that point we can correct the mis-triggers. And they still look like they have just a slight bit of potential air trapping. So whatever's driving this rate of 25 would be my next thing that I, or 29 would be my next thing that I would really wanna figure out. So with that, thank you for listening to us. Hopefully you found this useful in recognizing and managing patients with some common issues there. We thank you and we have a few minutes left here for questions. So if you wanna ask us questions, we'll be glad to answer them for you. And again, thanks for showing up this afternoon. Thank you.

ventilator graphics

dysynchrony

scalar graphics

mechanical ventilation

patient management

individualized treatments

inspiratory and expiratory times

flow rates

circuit leaks