The next 20 minutes, pulmonary waveform analysis, airway graphic analysis, basically just picture recognition. All right, here we go. Airway scalars. All of the vents are going to be a little different, but conceptually, airway pressure, airway flow, and volume over time. Top left here, this is going to be what? Square wave constant flow ventilation, normal, about as normal as it gets. Variable decelerating flow, normal as well. Simple take-home point, not so much for the boards, but for real life. If you're looking at airway scalars and you want to know whether a patient has good patient ventilator interactions or not, simply look at your flow versus time scaler and ask yourself a simple question. Is it pretty and symmetric, or is it ugly and asymmetric? Pretty and symmetric, you have good interactions. Ugly and asymmetric, you got a problem. Doesn't tell you what the problem is, but you know there's a problem. That simple piece will answer a lot of questions and help you both clinically and possibly on the boards. Airway loops, mostly what you're going to be looking for is your flow volume loop should look like an egg. Broad part of the egg up top, inspiration, narrow part of the egg, exhalation. This is normal. Pressure volume curve, normal as well. No lower inflection point, no upper inflection point. Okay, these are normals. And all these slides are in both the handouts you have of this talk as well as the full talk. So there's nothing here that you don't have. All right, types of dyssynchrony. Three different types. It goes right back to the components of mechanical breath, trigger, flow, and cycle. Trigger dyssynchrony, probably one of the more common ones, could be ineffective patient effort compared to the trigger sensitivity setting of the ventilator. It could be an inappropriate setting, whether the setting is too sensitive or too insensitive. And sometimes you'll get double triggering, and I'll show you an example of that. And that's almost always, even though it's a triggering dyssynchrony, it's almost always due to inadequate inspiratory flow. You can have flow dyssynchrony, I'll show you that in a moment. And the last is cycle dyssynchrony, where you're having, the patient's having difficulties transitioning from inspiration to exhalation, either due to premature cycling, air trapping, or delayed cycling. Come back to all these points in schematics momentarily. All right. Case to start, five-month-old chronic lung disease, viral bronchiolitis, intubated respiratory failure, SIMV, pressure control, pressure support ventilation, respiratory rate of 28, pressure is 28 over 7, and a pressure support of 12. Sedated with fentanyl and Prasidex. Patient experiences an acute episode of tachypnea, subcostal retractions, and agitation. Real schematic or real scenario you could get. And then they show you this. All right. So we walk through this. Top, airway pressure over time, bottom, airway flow over time. Pretty asymmetric, ugly asymmetric. Ugly asymmetric. So now you already know that the problem here is going to be some interaction between the patient and the ventilator. What do you see? Changes in flow without any corresponding significant changes in airway pressure. What is this going to be? Right? Bronchospasm, pain, flow asynchrony, triggering sensitivity, or air trapping. I already told you it has to be a patient-ventilator problem. So it has to be three or four. So what's happening here? The patient is breathing, but not triggering a breath, right? Triggering sensitivity. Okay. So this is a trigger to synchrony. What's going on if you look about this, look through this? Ventilator's deaf to the patient. Ventilator fires a time-cycled breath. There's time for a breath. What ensues? Chaos. This is the patient fighting the ventilator. Patient's not fighting the ventilator. The respiratory therapist or the clinician, basically, is fighting the patient. All right. Kind of a seemingly straightforward question. That may not be what you see. What you might see is this. Same exact scenario, but which of the following ventilator parameters is most likely to decrease oxygen consumption? Because this patient is wasting oxygen consumption. And the answer is going to be what? Fix the trigger sensitivity. Okay. It can look different. There's different ventilators, different schematics, and I'm showing you a whole bunch of different cut and paste from different machines so you don't just focus on one. Here's another example, right? You see a change here. Flows on the top. Always look at your labels. Change in flow without a change in pressure is another example of trigger dyssynchrony. And when you see dyssynchrony or asynchrony, interchangeable. Don't get confused on that. Another example here, you see subtle changes in flow with no change in pressure or tidal volume. Same thing. Air leak. Simple concept. Don't get fooled on simple things, okay? Any perfectly straight horizontal or vertical line is simply the airway graphics package connecting the dots. There's nothing physiologically that goes perfectly horizontal or perfectly vertical. Here what you see is here's a breath. This direct horizontal line is what? The ventilator can't see a signal. It can't see anything because you have a huge air leak, right? And you can measure that either on the digital display or simply looking at the difference between this horizontal line and baseline. And then down here what happens is the ventilator has to get, the graphics package has to get back to zero to start the next breath, right? Big air leak right here. Other point on the loops here, on the flow volume loops, you see the same thing here. Flow ends here, gets back to baseline. Now I'll tell you that you'll see a similar example later. The difference between an air leak and extreme increased expiratory resistance is really hard to tell because in both points, the measurement, the x-ray valve or the flow pneumotachometer can't see the flow because it's either not there or so slow. You can't tell the difference here between a true air leak and extreme expiratory resistance. No one's going to ask you that because you can't tell the difference based on graphics. You've got to do it based on general clinical assessment. So don't worry about that difference. Auto triggering. The ventilator fires itself. Tip off here is what? Huge air leak. That's where he went through. And with the huge air leak, each breath on flow here triggers directly from the end of the prior breath. As soon as flow hits zero, the next breath fires. So when you see this, no lag, no pause, no difference between expiratory flow and inspiratory flow with a large air leak. This is going to be auto triggering the air leak, the ventilator's triggering itself. Double triggering. Look at what you see here. So here's your flow. The answer's always going to be in flow. Two inspiratory efforts here for one breath. So double flow. The patient's pulling, doesn't get what she or he wants, pulls again to get full flow. Even though this is a triggering problem, the real issue here is inadequate flow or inadequate support because the patient's trying to get more gas flow than the initial inspiratory effort is giving him or her. Flow synchrony. Flow synchrony is the ideal matching of inspiratory flow of event breath to inspiratory demand during an assisted or supported ventilatory effort. Dyssynchrony, the opposite. It's inadequate flow at any point during inspiration causing increased or irregular patient effort. This then leads to increasing worker breathing and quote the patient fighting the ventilator. So here's an example. The arrows obviously are meant to help you out here. So if we look at this, here's your inspiratory flow over time. There's no flow pattern I showed earlier that looks like an M, right? So what kind of flow pattern is this? Square wave constant flow. But in the middle of the inspiratory effort, the patient's not getting the flow that she or he wants and what happens? The patient pulls again, pulling a downward deflection in flow trying to get more flow from the machine is capped and then comes back to baseline. So this is flow dyssynchrony, a patient's not getting adequate flow. It's the M sign just because it looks like an M and you see that here in each of the mechanical breaths. Just knowing and you wouldn't know this just from the graphics except for the difference in size of the breath presumably. This is a press-supported breath which is a variable flow breath and you don't see that because the patient here is getting the flow that she or he wants at each point in the inspiratory cycle. Cycle dyssynchrony. This is now the transition again from inspiration to exhalation. It's the failure of airway pressure and generally flow to return to baseline prior to the next ventilator-assisted breath. It's an inadequate or inappropriate IDE ratio. The inspiratory time tends to be too long, the expiratory time too short. These next terms are all used interchangeably so don't get fooled by them. Premature termination of exhalation, intrinsic PEEP, dynamic hyperinflation, gas trapping, it's all the same thing. So what's the problem with cycle dyssynchrony or generally called intrinsic PEEP? Patient has increased work of breathing. They have an increased mean interthoracic pressure which could decrease cardiac output as we talked about earlier. Can affect trigger sensitivity especially in the pressure triggering mode which we rarely see anymore. But most importantly are the last two bullets. If the patient has a set, is in a pressure limited breath with a set PIP and the ceiling is fixed, the PIP is fixed, if the patient has intrinsic PEEP, the floor is higher, then what happens? Tidal volume is going to fall, CO2 will rise. On the other point, if you have a set delta P or a set tidal volume approach and the floor rises because intrinsic PEEP is above PEEP, the ceiling rises as well and peak pressure rises. So the changes in your tidal volume and your peak pressure will depend on whether it's pressure set or volume set mode. But either way, the PEEP is higher than you have intended to set. Here's what it looks like. This is intrinsic PEEP where each breath in yellow here, each inspiration is occurring from just below the horizontal zero axis. Intrinsic PEEP. Adverse effects of intrinsic PEEP. You have potential ultra structural injury to respiratory muscles due to increased work of breathing. You have worsening respiratory mechanics we already talked about related to the increase in intrinsic PEEP. Gas exchange can be altered. Occasionally you can waste the patient's respiratory work, waste caloric intake. You can confound lung protective strategies due to breast stacking and the increase in peak pressure I've just mentioned. Patient becomes uncomfortable, phragmatic sleep, often is treated with increased sedation which leads then to increased length of ventilation and withdrawal symptoms and often simply confuses clinicians. Does it really matter in terms of outcomes? It does. There's an older study here from DeWitt in critical care medicine showing that asynchrony here, the ineffective effort greater than 10% leads to an increase in duration of ventilation, decrease in 28 day free, ventilator free days, increased ICU stay and increased length of hospital stay. So these effects do have negative outcomes on patients. All right. So overall, patient ventilator dyssynchrony can result in an agitated patient with increased work of breathing and increased oxygen consumption. If you can minimize patient ventilator dyssynchrony, hopefully you'll decrease O2 consumption and improve cardiorespiratory interactions. Hands-on prevention. This is kind of basically this is a labor intensive role for both the clinician and the respiratory therapist to assess airway graphics and respiratory mechanics regularly, avoid dyssynchrony and always assess the airway graphics and adjust the ventilator settings before knee jerk giving sedation. Sedation always works. Why does sedation work? Because the patient no longer cares that she or he can't interact with the ventilator. Always works. Generally the wrong thing to do. All right. Other points here. I mentioned earlier NAVA. I don't know that you'll see it and as faculty of this course, we're all arms length from the boards itself so we really don't know exactly what they're going to show just from our own personal experiences, but I put this up here just in case. So NAVA is using the electrical activity of the diaphragm to trigger a breath, presumably improve synchrony. There are some studies that show that, that you can improve trigger synchrony or avoid dyssynchrony by using the diaphragm to trigger a breath as opposed to the actual movement of gas. Not sure you need to know much more than that. All right. Let's move on to the other side of the equation. Now exhalation, the over distention. Over distention is an increase in airway pressure at the end of inspiration without a significant increase in tidal volume. It's beaking, goosenecking. Everyone calls it something different. This is what it looks like. But you're not going to get that as a question. You're going to get the question being over distention is objectively defined as what? Well, it's not beaking at inspiration because that's really not very objective, but it's one of the other three or four. Is it related to C20 over C total greater than 1, C20 over C total less than 1, dynamic compliance less than static compliance, or static compliance less than 0.5? What is it? If you think about it, okay, you know, test taking skills, it's probably one of these two because they're linked and they just go in the opposite direction. So it has to do with what? We talked about goosenecking, but it's really an upper inflection point. The upper inflection point, what happens? The slope of the compliance decreases. So if the slope of the compliance of the last portion of the breath decreases, then C20 or the compliance of the last 20% of the breath has to be less than C total, and thus the answer is C20 over C total is less than 1. You can see that here by the slope of blue, which is C20, compared to red, which is total compliance. All right, case two, six-month-old, chronic lung disease in your ICU after respiratory arrest on the wards, infant awakens, experiences an acute episode of agitation, tachycardia and hypercarbia, perinatal CO2 monitoring. This is a real case. What's the patient have? No one wants to bronch the patient and look at the airways, but the answer is right here. What is this? Okay, so flow over time, pretty symmetric, pretty ugly asymmetric. Well, it is actually symmetric. That's surely not a pretty trace. There's nothing normal about this. Flow goes in, hits an obstruction, ventilator says, I'm not done with the breath yet, gives more flow to finish the breath. What's the obstruction? Bronchospasm, tracheomalacia, water in the circuit, mucous plug in your pneumothorax. You argue, well, it could be more than one thing. I say, no, it can only be one. Sometimes some of the questions will say, that's a bad question because it's more than one answer. There's really only one here. What is it? Tracheomalacia, okay, right? Fixed obstruction, airway collapse. Flow hits the airway collapse, and then the ventilator and the variable decelerating flow gives more flow to complete the breath. How do you know it's not, well, it's definitely not one, how do you know it's not water, mucous, or mucous plugging? I'll show you that in a second. This is what flow volume loop looks like, exact same thing. Flow goes in, hits obstruction, and then continues. Same camel humping as you saw, just a different graphical display. What's this? Similar, but what's the difference here? It's not consistent. Every breath is a little different. So what's this obstruction? Secretions, right? Malacia is fixed, secretions are going to be moving. Now you can argue that a cemented plug can look like malacia, and I can't argue with that. But common things being common, you know, this is secretions. These pictures are taken seconds apart. How did this suddenly get better? Patient wasn't suctioned. No, look at the mode. Variable decelerating flow. The flow is variable, and the ventilator is trying to get by the obstruction. Square wave constant flow, nothing changes. But if you did a head-to-head comparison, peak pressures would be a lot higher to get by the obstruction with a constant flow. Water in the circuit, vibratory, looks like a fine sawtooth pattern. Always looks like this throughout inspiration and exhalation. That's water in a circuit. All right. Optimizing PEEP. Go through this quick pressure-volume curve here. Lower inflection point. The point up to the lower inflection point, that is your recruitment interval. Treatment here is what? Increased PEEP. We're not going to go through here how much to increase because they're not going to ask you that. The issue here is increased PEEP. Okay. Increased expiratory resistance. See two different ways here. On this schematic, a long tail. Here failure to return to baseline. Need to take that in context of the clinical stem that they would give you. But this is the picture. This is what it looks like. Pattern recognition is the key with airway graphics. All right. Increased expiratory resistance here on your flow-volume loop, same thing. This point, again, as I mentioned earlier, you can't tell the difference between increased expiratory resistance and air leak. Either way, the flow is too low for the sensor to pick it up. Will not ask you that difference. All right. Indexatory lung volume. If your indexatory lung volume is too low, compliance falls, tidal volume falls, respiratory rate increases. May result in premature termination of exhalation and intrinsic PEEP. And then the increasing opening pressure needed may result in an increased risk of barotrauma. On the other side, if the indexatory lung volume is too high, pulmonary overdistension and risk of valutrauma. Increased expiratory resistance, the obstruction to exhalation can be caused by any obstruction in the system, airway obstruction, endotracheal tube occlusion. Could be bronchospasm. And then kind of the trick there, sometimes more real life than on a board question, you have a problem with the expiratory valve. Increasing the blocking expiratory flow. Prolonged expiratory phase leads to, again, gas trapping, increased work of breathing. And as we cycle back to the beginning of this session, could affect trigger sensitivity. That's all I'm going through in terms of basic airway graphics. All these pictures and everything are on all your slides. If you have questions and want to go through them again, please ask. But this is simply pattern recognition. What is the asymmetric and what is the pattern? Just have to have these recognized. In my last couple of minutes here, I'm going to switch gears just a little bit and go into capnography. Top panel, esophageal intubation. Often you see, and we know this in real life, some CO2. This is why the color change devices are not good. Because you'll see a color change device, RT whips it out, says you have CO2 and you don't. What is this? What? Probably CO2 entrained in the stomach due to bagging. Or if you're in the ED system, ED world, what? Carbonated beverage drank right before the car accident. Real life. Mainstem intubation. You can see this. I've seen this. What is it? Camel humped. Tenuated look of the tracing. The gray is what normal would look like when you see this and it doesn't extinguish. It stays constant, especially if your breath sounds a little isometric. Think about a mainstem. Bronchospasm. One question that often comes up is the bronchospasm, what's the end tidal CO2? Is it low or normal? Is it falsely low or does it match PACO2? Well it depends on whether you fully exhale. So a couple of points here. For an end tidal CO2 trace, bronchospasm looks like a shark fin. That's bronchospasm. If you have bronchospasm here where you don't reach full exhalation, the end tidal CO2 will be lower or falsely lowered by the fact that you don't have full exhalation. If you have full exhalation, then the end tidal CO2 is more accurate. And lastly, you often will not use capnography to look at dyssynchrony or trigger insensitivity, but you could. Airway graphics, ventilator graphics is a little clearer, but you can see it here. Here's a patient taking inspiratory efforts during what should be exhalation. And here's a patient trying to take an inspiratory effort, and the ventilator's not responding. So you'll see the same thing as you can see on the airway graphics here in capnography, just a little bit harder, especially given the size of the displays. So with that, I'm going to conclude, and the big thing here is just assess. Just keep assessing your patient in the airway graphics. Look for trigger, dyssynchrony. Look for auto triggers. Look for flow dyssynchrony, and look for cycle dyssynchrony. In terms of assessing auto triggering versus tachypnea, you need to assess whether the patient has an air leak. Sometimes you need to adjust the trigger sensitivity, and sometimes you have to do a disconnect to be able to see what the ventilator's doing compared to the patient. Overall, if in doubt, as I said earlier today, the answer is always flow. Adjust flow, assess flow. And lastly, assess for intrinsic PEEP and adjust the eye time, or switch to a flow-cycled mode of ventilation and let the patient choose the eye time. Asthma, what do we want to try to do in intubated asthmatic? Get the patient to press sport so she or he can adjust their own inspiratory and expiratory time. With that, Annalia's telling me my time's up.

pulmonary waveform

airway graphic analysis

ventilatory patterns

patient-ventilator interaction

dyssynchrony types

capnography patterns