Mechanical ventilation management requires understanding five core settings: FiO2 (oxygen concentration 21-100%), PEEP (positive end-expiratory pressure 5-10 cm H2O to prevent alveolar collapse), tidal volume (6-8 cc/kg ideal body weight for lung protection), respiratory rate (16-20 breaths/min), and inspiratory pressure (controlled in pressure control modes). Oxygenation is managed through FiO2 and PEEP, while ventilation (CO2 clearance) is managed through respiratory rate and tidal volume. Peak pressure reflects airway resistance, while plateau pressure reflects lung compliance; both should be monitored to prevent barotrauma. Spontaneous breathing trials (SBTs) with pressure support (5-8 cm H2O) are the gold standard for assessing extubation readiness, with RSBI <105 predicting successful liberation. Daily SBTs with sedation interruption reduce ventilator days and improve mortality.
First Month in the ICU | Mechanical Ventilation Made Simple (Full Crash Course)追加:
All right, everybody. Welcome back to another episode here at Whiteboard Medicine. We appreciate you checking it out. Today's episode we're really excited about. Picture this, if you will. First week in the ICU or first week back after a hiatus or just looking to brush up on some foundational skills.
You walk in and suddenly every patient, every other patient is on mechanical ventilation, numbers, modes, alarms, beeping. There's a lot happening. And if you don't have a good foundation, it's not always clear what all these variables mean, how they matter. In this episode, we're going to break down the basics of mechanical ventilation into a simple structured approach from core fundamentals to modes and troubleshooting to understanding peaks and plateau pressures, how to wean mechanical ventilation, and then even how to present it confidently on rounds.
Think of this as your road map. Set up, interpret, troubleshoot, liberate, present. If you can internalize the framework in this episode, you can walk into any ICU and immediately start making sense of all the patients on mechanical ventilation. If you want to go deeper than this episode, we did just want to let you know that we have built a full emergency critical care curriculum with study guides, practice questions, ad free videos, mini courses, medical education post, hundreds and hundreds of resources. probably one of the biggest collections of emergency critical care medical education content out there. Um, and we built it all on our Patreon page. We're really excited about it. We've had tons of positive feedback, tons of folks joining. So, consider checking that out if you want to dive even deeper than this episode.
It's linked in the episode description as well as the pinned comment on YouTube. No further ado, let's get into mechanical ventilation point and talk about mechanical ventilation core settings. PEEP, FiO2, respiratory rate, title volume, and inspiratory pressure.
And this will get into volume control and pressure control just a little bit, but we're going to talk about what each of these variables and settings are, why they're important, when to titrate them, where to start with them, and all that good stuff. So, by the end of this episode, you should at least have a good foundational grasp on the most important portions of mechanical ventilation settings, which would be these five variables. So, no further ado, let's dive in. Starting with the fraction of inspired oxygen. What is it? Well, the fraction of inspired oxygen, also known as the FiO2, is literally the percent of oxygen being delivered to the patient. So every time a breath is given, this is the percent of that air that is oxygen. And the range here is going to be starting at 21%. Because at sea level, right, 21% of the air we are breathing is oxygen. As I stand here right now, 21% of the air I am just taking in of room air is oxygen.
So we don't tend to go lower than 21%.
But you can go 21% all the way up to obviously 100% FiO2. This is the maximum. This means all the air being delivered on the ventilator is all oxygen, right? 100% of it. So you can't go higher than 100%. Now, sometimes when we're titrating ventilators, people are hesitant on the FiO2 to go, you know, lower than 40% or lower than 30%. Right?
Often times we'll hear that 40% is minimal or 30% is minimal. Just know that, you know, this is somewhat just arbitrary and made up. You certainly can go down to 21%. Um, this is all just intended to be educational and opinion.
None of this is intended to be acted upon as medical advice. Um, our practice pattern though tends to be that we'll go as low as 30%. Every once in a while for a patient that's got a prolonged ventilatory course, we'll take it down to 21%. But um, we usually stop at 30%.
That's just a practice pattern thing.
Um, too much oxygen hyperoxia superoxia is um, injurious, right? You get free oxide radicals and all these things that can cause local um, injury to the lung.
Um, you can get something called reabsorption adalcttois as well. So um, too much oxygen is certainly bad. you want to titrate that FiO2 down as you're able. Um, but just know that this 40% or 30% is arbitrary, but 21% is the real lower value you can do cuz that is the auction percent at room air. And we should say actually while we have you that if you want this study guide, this PDF, what we're literally going through today, this exact document, you can download it on our Patreon page. We have an wonderful Patreon community on all things emergency critical care medicine.
Gosh, it's probably one of the largest collections of emergency critical care educational material out there. We got full emergency and ICU curriculums, ad free videos, every single study guide for all the videos, um practice questions, mini courses, medical education posts, gosh, a numbering in the hundreds at this point. So, we've been putting a lot of time into it.
We're very excited about it. We've had a lot of uh great feedback and a lot of people join in and we'd love for you to check it out. So, if you're interested or if you want to download the PDF for this episode, print it out, download it, annotate it, whatever you want, um, check out our Patreon page. It's linked in the episode description as well as the pinned comment on YouTube. All right, sorry about that. We just want to make sure you have that tidbit of information while we're going through all this. So, what does the FO2 do?
We've talked about this a little bit, but this directly increases the alvolar oxygen concentration. And if we're going to break down what that means, our lung is composed of just, you know, up to thousands of alvoli. You know, these are these little kind of balloons and they have blood vessels on the outside of them. They're very thinwalled and air travels in them, expands the alvoli or alvolis um and then that oxygen diffuses into the bloodstream. Carbon dioxide, let's just get a different color. Carbon dioxide diffuses out of the bloodstream into the alvoli. Then when the breath is done, the alvololis contracts. That carbon dioxide is pumped out of the alvolus and it travels, you know, into bigger and bigger airways eventually into the bronchi, trachea and then out of the mouth and that's how you expel carbon dioxide. So increasing the FiO2 is just going to directly increase the alvolar oxygen concentration. The higher the FiO2, the higher percent of oxygen in this alvoli so that your bloodstream can absorb higher concentrations of oxygen.
And this improves oxygenation. And that's a concept that we're going to come back to. We're going to be talking about some of these settings in terms of oxygenation.
And then the other variable we'll be talking about is ventilation.
Oxygenation is literally the oxygen saturation. So increasing FiO2 increases oxygenation. Ventilation is how well we're clearing carbon dioxide.
Increasing FiO2 doesn't directly change ventilation, although there is some complex physics that can occur um that can help with CO2 removal, but that's probably since we're trying to uh keep this as kind of a foundational discussion. Uh not part of the discussion currently. So, FiO2 increases oxygenation. It doesn't do anything for ventilation or carbon dioxide removal.
So, how to set the FiO2? Well, most commonly when you first put a patient on mechanical ventilation, you'll just put it at 100% because you don't know how the patient's oxygenation is going to change after you perform endotracchial intubation. But what you really want to do is you want to make sure you rapidly titrate it down cuz you want to avoid oxygen toxicity like we talked about.
And oxygen toxicity is both local free oxide radicals that can cause damage um as well as you can get something called reabsorption adalcttois which is where parts of the lung actually get adalctatic when there's too high percentages too high of a percent of oxygen. Typical target you know is 88 to 96% somewhat disease dependent. Um the key here is you want to avoid both less than 88% and more than 96%. hypoxy and hyperoxia um both are injurious to the lungs in the body. So key concept here FiO2 is a temporary fix for oxygenation.
Um one thing to note that the will get into is you know most people say although it's not necessarily robustly um evidence-based but most people say that if your ventilator has a setting of an FO2 more than 60% that is when you start to get some of those things like local free oxide radicals and reabsorption adalcttois.
Um, so if it's more if your FO2 is more than 60%, you should really think about increasing your PEEP. All right? And we'll get into that more in the next section, which is PEEP. PEEP stands for positive endex expatory pressure. Now, let's think about what that means.
Positive end expatory pressure. What that is, it is the pressure in the ventilator that it is giving. That's already doesn't make sense. It is the pressure that the lungs are experiencing at all times. And the reason it's named this is because um when you get a breath, right here's your trachea. If you're listening to this in podcast version, don't worry, you're not missing too much. We're just doing a bad drawing of a trachea and lungs. When you get a breath, right, it pushes air in trachea broni into smaller smaller bronchioles and it inflates the lungs and that creates an amount of inspiratory pressure. But when that breath is done, those lungs deflate and that air travels back out of the trachea. At the end of expiration, there's obviously no inspatory pressure. So the PEEP is the pressure at the end of expiration, the positive end expiratory pressure. And this is the setting on the ventilator.
You know, ventilators have it all different, but usually there's a screen um screen maybe in the top right corner has the peak pressures. Um there's usually some variables on the left side.
This is obviously brand dependent. And then on the bottom there's usually a couple settings, you know, FiO2, which we talked about, respiratory rate, which we will talk about, PEEP, which we talked about, and title volume, which we will talk about. If it's a pressure control mode, this is going to be inspiratory pressure instead of title volume. Um, but we talked about FO2, we're talking about PEEP now. So, you set the PEEP. The PEEP is a number that you set on the ventilator, which is the amount of pressure that those lungs are experiencing at all times. Even at the end of expiration, they're still experiencing that pressure. And why we do that is it prevents alvolar collapse.
Remember that drawing we did above where you have all these alvoli right up to thousands of them and they're very thinwalled and if there's no end expiratory pressure exerting some force on these thin walls they'll collapse down and this is adalcttois right if you have the shrivel collapse down alvoli that's how you get adalctatic. So uh positive and expatory pressure continues to exert a small amount of expatory force on these thinwalled alvoli to keep them open, keep them recruited is a word we often say and prevent them from all collapsing and causing adalcttois.
So what does it do from an oxygenation ventilation standpoint? Well, remember we said oxygenation is literally the amount oxygen in the blood, right? Oxygen saturation is a manifestation of that and that's compared to ventilation which is the amount of carbon dioxide. So oxygenation controls oxygen in the blood.
Ventilation controls carbon dioxide.
PEEP improves oxygenation and it does this by keeping alvoli recruited so that they can exchange air, right? Because if our alvoli are all collapsed down, those blood vessels that are supposed to be absorbing the oxygen, they're not going to be exposed to oxygen cuz the alv alvoli is all collapsed down. So when you're trying to breathe air in, it can't even get to the alvoli cuz the alvoli is collapsed and at lectic. So none of the air can actually get to the blood vessel to get absorbed. Whereas if you have that PEEP and you have this nice and recruited and open, all that air you're breathing in can get into the alvoli and then get reabsorbed into the bloodstream. Right?
So it recruits uh recruits collapsed alvoli and improves VQ matching. This gets into a concept called functional residual capacity. Um it does increase that. I think we're probably just going bypass that cuz that's going to be a whole rabbit hole that probably is a little more on the uh intermediate side of complexity. So, how to set the PEEP?
Just like we talked about the FO2. So, we said FO2 you usually start at 100% and then you wean down as fast as you can. The PEEP PEEP for just the run-of-the-mill person, starting it at five is not unreasonable. Five is what we kind of consider quote unquote minimal PEEP, but this is very um pathology dependent. Okay. If you have lungs that have pulmonary edema or pneumonia or diffuse alvolar hemorrhage um or anything else, you know, blood pus, water, all of that usually requires a little bit higher PEEP cuz those pathologies lead to more alvolar collapse. So you need more PEEP to keep those alvoli recruited. Whereas if you have someone who is intubated just cuz they had a huge stroke and they're confused but their lungs are okay, then five of PEEP's plenty. We don't usually go less than five of PEEP. There's some unique scenarios where some people talk about ZEP uh ZEP or zero PEEP um but we don't tend to believe in those necessarily and uh our minimum is five a PEEP but if we have a patient who's got really bad pulmonary demmer pneumonia or diffuse alvolola hemorrhage and they need to be intubated for refractory hypoxmia we might start their PEEP at something like 10 rather than five but again this is a matter of weaning down.
Now, key trade-offs here, right? The benefits in oxygenation from PEEP is totally dependent on how distended the alvoli are. So, if we're if we draw three alvoli and you have one that's collapsed down, you have one that's perfectly distended, and then you have one that is what we call over distended, the patient that's going to benefit from more PEEP is going to be the one that is under distended or collapsed. Because if I increase the PEEP, that will make this more collapsed alvololis more optimally distended which is going to improve our oxygenation. But if we are already optimally distended or we're overdistended, increasing the PEEP is actually going to worsen oxygenation because it's just going to cause worsening over distension and that's going to damage the alvoli and they're not going to be able to absorb oxygen efficiently. So increasing PEEP does not magically just increase oxygenation. It only increases oxygenation if there is recruitable lung units available. Aka there's portions of the lung that are under distended or collapsed that you could recruit by increasing PEEP. All right.
The other thing to note here is FiO2 improves oxygenation quickly because you're literally just increasing the amount of oxygen being delivered to the alvoli. PEEP though takes time. All right. um it is not often an immediate magical fix. It also takes time to see what happens if you're going to decrease the PEEP. So when you're making ventilator changes, FiO2, you'll see the effects quickly, usually in a matter of minutes. PEEP often takes hours to see the effects, at least the full effects.
So FiO2 titrations, you can do quicker PEEP titrations, you certainly should do low and slow, right? Don't overdo it because if you overdo it, you'll either lead to overdistension, but it'll take an hour or two to realize it and then you'll be way behind or under distension in the same thing. An hour or two to realize it and then you'll be way behind. All right. What about title volume? So on our vent settings, we, you know, talked about FiO2, we talked about PEEP, now we're talking about title volume.
And just know that title volume is only a setting that we change and set in volume control mode. And on our channel, we've talked about volume control and pressure control and tons of mechanical ventilation stuff. So, if you want to look that up, just search whiteboard medicine volume control. Uh, and we'll have a ton on it. But just know if you are on a pressure control mode of ventilation, you're not setting the title volume. So, if you're on volume control, that is when you will set the title volume. And the title volume is literally the amount of air being delivered with each breath. Right? Do you want 300 cc's of air? Do you want 500 cc's of air? It is quite literally the volume of air being delivered with each breath. And what it does is it helps with what we call minute ventilation. Right? You're starting to see ventilation now. Just like FiO2 was oxygenation and PEEP was oxygenation.
Title volume is ventilation. And we talked about that ventilation is what clears carbon dioxide. So title volume is part of minute ventilation. And we've talked about minute ventilation on the channel before as well, but minute ventilation equals respiratory rate times title volume. This is literally the cc's of air that the lung is getting delivered every minute, right? Because it's the title volume, which is the amount of air delivered with each breath, times the respiratory rate, which the amount of breaths per minute.
So it makes sense that that is the minute ventilation. And this helps with CO2 clearance, right? because you're going to have more minute ventilation that the CO2 is going to be able to diffuse into the alvoli and then you could breathe that out. So, how do we determine the most appropriate title volume? Well, usually we start with something called predicted body weight.
Um, sometimes we actually call it ideal body weight. Um, and this is just based on a patient's height. Um, because everyone's thoracic cavity is about the same size depending on your height. Um, no matter how much you weigh. So, someone who is 5' 10 in uh and weighs 100 lb, their lungs are similar in size to someone who's 5' 10 in and weighs 400 lb. So, we don't want to use the 400 lb to calculate things because their lungs are the same size as the 100 lb. So, we use the ideal body weight based on the actual height of the patient rather than the weight. You could just look this up.
Uh we don't get any money from MD Calc or anything like that, but we usually just type in MD Calc, ideal body weight, and you can just put in the patient's um height, and it'll kick out their ideal body weight number. And typically what we shoot for is about 6 to 8 cc's per kg of ideal body weight. And the reason we do this is because there's been some trials in lung protective strategies um where going above that can sometimes be injurious to the lungs and lead to ventilator induced or associated lung injury, right? because the amount of air you're pushing in is going to inflate those alvoli. So if you have too much air being pushed in, it's going to overdistend those alvoli and cause trauma. All right? So 68 cc's per kg of ideal body weight is a nice start. So if someone's ideal body weight is 50 kg, you know, a nice start is something like uh uh 400 cc's would of title volume would be 8 and then 300 cc's of title volume would be 6 cc's per kg, right? Um so someone's 50 kilos 3 to 400. You know, someone who's a more kind of regular size is about 70 kg. So you can see six times that would be 420 cc's of tital volume per breath. A lot of times you'll see uh respiratory therapy if you have them will just kind of set the title volume at about 450 which works for most people unless they're on the um um uh higher low end of the height spectrum you know like less than 5t or greater than 6 ft. Key concept here larger title volumes is better CO2 clearance but larger title volumes can be injuries to the lungs. So stick to that 6 to 8 cc's per kg. Smaller title volumes can be longer uh protective, but it can cause increased CO2. Um, now we often will allow for something that we call permissive hypercapnea, but that is a little outside of the uh purview of this episode. Um, again, we've talked about it a whole bunch of times, so just look up whiteboard medicine permissive hypercapnea and it'll come up.
All right, let's see what we got left.
Next is the respiratory rate, right? So again, here's our ventilator. Here's the settings that we set. And we talked about the FiO2 which helps with oxygenation. We talked about the PEEP which primarily helps with oxygenation.
We talked about the title volume which helps with CO2. Now we're on the respiratory rate which is also going to help with ventilation or CO2. We talked about FiO2. We usually set at 100% but wean down as quick as you can. And the changes to Fio2 are seen pretty quickly.
We talked about PEEP which usually starts somewhere between 5 to 10 but it's um pathology dependent. and know that changes are seen more slowly. So don't make changes quickly. We talked about the title volume which we do six to eight cc's per kg of predicted or ideal body weight. And now the respiratory rates. The respiratory rate as one might think is the number of breaths delivered per minute. Okay. What it does is it also controls minute ventilation. Right? We talked about tital volume and minute ventilation.
Well, respiratory rate is that other variable and this is the main determiner of CO2 elimination.
Typical starting respiratory rate is physiologic. Right? We breathe about 16 times per minute. So most people will set the respiratory rate 16 to 20. Now do note that this is also pathology dependent.
If you have someone who's academic, metabolic academia, who's breathing 30 times per minute and you have to intubate them, which goodness forbid because that's a patient that intubating them and taking away the respiratory drive might be deadly. But let's say you have to. You don't want to start them on a rest at a 12. They'll die, right?
Because when you intubate someone, you're taking over their ability to compensate for metabolic acidosis. So if they're, you know, academic from a metabolic standpoint, you might be starting that respiratory rate at something like 28, right? The catch to this though is patients can only tolerate so much respiratory rate on mechanical ventilation. At some point, they will start doing something called auto peep. And auto peep can actually worsen CO2 levels and can kill patients.
And not to be a broken record, but we got episodes out on auto peep, too.
Search whiteboard medicine auto peep and it will pop up. All right. So, uh higher respiratory rate you'll clear more CO2 usually but you will risk air trapping and auto peep. Lower respiratory rate you can risk hypercapnea or worsening academia because you are not compensating for metabolic acidosis if they have one. So CO2 high think about increasing respiratory rate first rather than tital volume because that's more lung protective probably. But be very cautious of auto peep. All right, last but not least is the inspatory pressure.
And we put this on here because when we draw our ventilator settings, right, we said FiO2 is one that we can pick and set.
PEEP is one we could pick and set. Title volume is one we could pick and set. And then respiratory rate. But title volume here, like we said, is uh only a variable that you pick and set when they're on a volume control mode of ventilation. The other mode we commonly use is pressure control, right? And in pressure control, you still set the FiO2, you still set the PEEP, you still set the respiratory rate, but instead of the title volume, you're going to set an inspatory pressure because it is pressure controlled. And this inspatory pressure then develops a tital volume, but you're not controlling the title volume, you're controlling the inspatory pressure. So, just for an example, right, let's say you set the inspatory pressure at 10.
That means the ventilator is going to give a pressure of 10 millimeters of mercury with each breath. And whatever those lungs take for their tital volume is what they take based on their compliance and all that kind of stuff.
So maybe an historic pressure of 10 creates 200 cc's of tital volume. But this number might vary, right? If they get sicker, maybe in an hour it's 150 cc's. Or maybe they get better and in an hour it creates 250 cc's of title volume. If you want more title volume, you have to increase the inspatory pressure, right? Let's say you increase it to 20. that might then lead to 400 cc's of title volume with each breath.
So the tital volume becomes the uncontrolled variable and the inspatory pressure is what you're controlling and this is only in pressure control modes.
So uh inspiratory pressure is the pressure applied during inspiration which determines how much air flows into the lungs. It controls the tital volume indirectly based on lung compliance and airway resistance. to set it uh we usually use the developed title volume to set it. Right? So if we want the title volume to be 6 to 8 cc's per kg, we will pick an inspatory pressure.
We'll look to see what the title volume is and then we will increase or decrease the inspatory pressure to try to get to the adequate title volume. But we are always watching what this inspatory pressure value is because we don't really want it to go above 30, right?
because that can start to be injurious to the lungs as well. All right, so you know, you could choose whatever inspiratory pressure 10 or 15. Um, make sure you don't go above 30 and then titrate it to achieve the title volume you want. Um, but just know that that might change breath to breath, hour to hour, right? The title volume might be higher or lower just depending on how the patient is doing. So the pressure is what you set and the volume is the variable that's uncontrolled. So when you want to limit airway pressures, this can sometimes be helpful. Um because the airway pressure maximum is what you're actually setting is the inspatory pressure. Um whereas in if you're setting the title volume in a volume control mode, the uh peak pressure, the pressure that is being developed is the uncontrolled variable. Okay. Um whereas when you're setting an inventory pressure, that's the controlled variable and the title volumes becomes uncontrolled. Again, this is a little complex, but just check out our episodes pressure control and volume control.
It'll all make sense. So putting this all together when we think about oxygenation versus ventilation. If we need to improve oxygenation, FiO2 is the quick fix and PEEP can be the fix depending on if there's alvoli to be recruited to fix the carbon dioxide levels. Respiratory rates the first fix.
Title volume can be something to consider too. Always monitor for auto peep.
Quick bedside approach. Low oxygen, increase the FiO2 first to buy you time and then consider increasing the PEEP as the clinical circumstances allow. High carbon dioxide, increase the respiratory rate first, assuming there is no auto peep.
And if you're unable to achieve your goal with the respiratory rate, consider the title volume, but only with caution.
Um, because this can actually really cause harm. Okay? So, part of us wants to just take that out, but um, you know, it's not unreasonable depending on the clinical circumstances. Key takeaways to wrap it up. FiO2 and PEEP are what drive oxygenation. Respiratory and tital volume drive ventilation. Inspatory pressure controls the title volume and pressure control modes. And always prioritize lung protection. Um just as a somewhat introductory concept here.
Mechanical ventilation is obviously uh someone who has been intubated. They have an endotracheial tube and intubation is a totally separate discussion. But the reasons for intubation tends to be things like hypoxmia or low oxygen levels. Um refractory hypercapnea uh and we could say refractory hypoxmia too but refractory hypercapnea um or high CO2 levels inability to protect airway. So airway protection that patient who is so altered that they're gurgly they're aspirating they can't protect their airway. Um anticipated clinical course is another one. uh if someone needs an operation uh and needs uh endotracchial intubation to go on a ventilator for their operation. That is another one. Uh and then the other part of airway protection is structural things too. If someone unfortunately had a gunshot wound in the neck and they had an expanding neck hematoma, uh they might need intubation to keep their airway patent. So these are kind of the four main things. There's a couple other ones, but this is a good way to start.
So this is how someone ends up on mechanical ventilation, right? You put the endotrachial tube in, you have to hook them up to the ventilator. When we intubate someone and put them on a ventilator, we have to set a ventilator mode. And this is something you choose or we choose as a team. Um, and there's a couple different ventilator modes. The two main ones are called volume control and pressure control. And we'll go into these down here, but volume control and pressure control, their two main ones.
Pressure control is more kind of front and center in pediatrics. At least that's what we've been told. We don't work in pediatrics anymore. Uh whereas volume control uh is often our starting uh mode in adults. Now there's certainly exceptions to this. There's some people in adults who still prefer pressure control. Uh in our clinical practice, we tend to choose volume control first, but then sometimes we do end up putting the patient on pressure control for different reasons. And there's lots of complexity here. But just in generalities for adults, we often start in volume control. Um, part of that is because a lot of the, you know, guidelines or recommendations out there for things like ARDS and what have you, um, are more centered around volume control. Um, although there's definitely definitely a role for things like pressure control, too. But instead of us blabbering about volume control and pressure control, why don't we talk about what they are? So, volume control or VC and this is often called assist control, volume control. The AC, the assist control, is something that's applied to both volume control and pressure control. just means the ventilator helps uh determine breaths given. Um but volume control, the main variable you're setting in volume control is something called the title volume. So anytime you put a patient on mechanical ventilation, there's kind of four different things that you're setting each time. There's way more than that, but these are the four basic things and it's PEEP, FiO2, respiratory rate, and then either title volume or inspiratory pressure.
And this is the difference between uh uh volume control versus pressure control.
So, we'll talk more about these in a second, but in volume control, you are setting the title volume. Okay? So you were telling the ventilator, you're like, "Hey, I want this patient to get about 500 cc's of tital volume with each breath." And the ventilator goes, "Okay, I'll try to give them about 500 cc's of title volume with each breath." This is in comparison to pressure control. In pressure control, instead of the title volume, you're setting an inspatory pressure. You're telling the ventilator, hey, I want you to give about 20, you know, centimeters of water above the PEEP every time you give a breath. And if we think about what this means, if you were in volume control and you're setting the title volume, the variable you are not controlling is the pressure that title volume creates. The ventilator is essentially just pumping in 500 cc's. It's a little more complex than that, but is essentially pumping in 500 cc's of that breath and then the pressure that that results with in the lungs is not controlled, right? That just depends on the patient and the uh path pathology they have going on.
Whereas in a pressure control, you're setting up pressure. So the variable that is um not controlled is the title volume because you're telling the ventilator I just want you to administer this amount of pressure with each breath and whatever tital volume that creates will depend on the patient and the pathophysiology they have going on. So if we think about this in a practical sense we're going to scroll over to the side. in volume control versus in pressure control. What you're going to see is when you set that title volume of 500 cc's, there will be kind of an inspatory pressure, also known as a peak pressure, that'll pop up in the corner of the ventilator screen with each breath. And every time that ventilator pumps in that 500 cc's that you set for the title volume, there will be a peak pressure that pops up. You know, it might say 28, it might say 32, it might be really high like 60. And we'll talk more about that in a second. But that variable is not controlled. You are controlling the amount of volume they are getting with each breath. Whereas the pressure is just secondary to the amount of volume you're giving them and the patient's pathophysiology. Whereas pressure control, you're setting that pressure. Right? You said let's give them 20 cm of water above their peak.
And then what you're looking at on the ventilator is you will see how much tidal volume this creates. That might create 300 cc's or maybe 350 or maybe 400. It just depends on the patient and their physiology. But that title volume with each breath is going to change. Uh whereas the inspatory pressure that you set is stable each time. Right? So volume control the tital volume is controlled and the inspatory pressure it creates that peak pressure is uncontrolled. Whereas in pressure control that inspatory pressure you're setting that is controlled.
Whereas the title volume that that creates is uncontrolled. that's going to change with each breath. And that gets into um what we have to be careful with.
Right? So in volume control, you get this consistent minute ventilation cuz minute ventilation, we've talked about this in previous uh episodes is the title volume times the respiratory rate, right? The minute ventilation is the total ventilation, total cc's breathed in 1 minute. So title volume times the respiratory rate, right? If you're breathing 12 times per minute and each breath you're getting 500 cc's that times respiratory rate is how many cc's of air you're breathing each minute because as we said the tital volume you're setting it and the respiratory rate you're setting it. So these are two variables you're controlling. there's a consistent minute ventilation but the pressure as we talked about is uncontrolled that peak pressure is dependent on the patient their physiology and it might change breath to breath whereas in pressure control you have controlled pressures because you're saying I don't want them to get more than this inspatory pressure right I'm setting an inspatory pressure and that's the pressure the ventilator is giving them but the tital volume is variable which means the minute ventilation is variable right because that t you're setting a respiratory rate in pressure control and you're also setting that inspatory pressure, but the minute ventilation they're getting is just going to depend on how many cc's of title volume that inspatory pressure gives them with each breath.
All right, patient effort for both of these is optional. You're setting a respiratory rate. So, patients can breathe over the ventilator. can uh prompt their own breaths, but if they don't, the ventilator will give them the respiratory rate that you're setting. It is assist control though, so they could take more breaths. If you set a respiratory rate to 12, but the patient wants to breathe 25 times, that ventilator will give them the assisted breaths all 25 times. All right?
Whereas, if they are not taking breaths of their own, that ventilator will just give them the 12 breaths that you set.
So it's not like the patient um is trying to breathe more but the ventilator isn't helping them with those breaths. The patient will be helped with as many breaths as they take but at the very least the ventilator will give them those you know whatever respiratory rate you set. This is in comparison to something like pressure support. So pressure support is often kind of what we call spontaneous breathing trial or SBT. Uh, and this is where the ventilator, all you're setting is kind of this inspatory pressure to help support them and help them overcome the resistance of the ET tube, right? They have an endotrachial tube going in their mouth down their throat and there's resistance to that endotrachial tube. It's like trying to breathe out of a straw. So, when you put someone on pressure control, all right, the patient or sorry, pressure support, I apologize.
When you put someone on pressure support, the patient has to take their own breaths. their patient effort is required. Right? This is a spontaneous breathing trial. They are taking these o these breaths. But every time they take a breath, the ventilator will give them a little bit of inspatory pressure to help them overcome the resistance of that endotrachial tube. And we can set this right. A lot of times it's seven or some people use 10. And you could set this really high. You could essentially make this a uh highly supported ventilator mode where you can set that inspiratory pressure just as high as you did for pressure control, right? You can set it at 20, but the patient still has to breathe on their own. They still have to prompt those breaths. So, we use pressure support during uh weaning trials because there are no backup breaths. the patient is taking their own breaths and the ventilator will not give them breaths unless they're apnic and not breathing in which case the ventilator will alarm and there's usually kind of a backup apnea rate. The ventilator won't just let them not breathe and you know have something horrible happen. Um but that's like an apnea backup alarm. Otherwise in a pressure support or spontaneous breathing trial the patient has to take those breaths on their own but they do get a little inspatory pressure support and again we can set this bedside. S IMV is not used very often anymore. Um, SIMV is essentially um a mode of ventilation where patients take their own breaths and also get supported breaths. And it used to be used as kind of this weaning uh uh modality where you could try to kind of give them more supported breaths and you decrease the number of supported breaths they were getting and if they did okay, it might mean they're able to get off the ventilator. but we don't really do that anymore and SIMV is not commonly used. So, we're not going to talk about it much in this basics lecture. If people are interested in SIMV, let us know. Uh, and we could put out a a video on SIMV in particular. And then CPAP is very similar to pressure support. So, we're going to kind of cross that one out as something we're going to dive into. These are going to be these three are going to be your three main foundational ventilator modes. Volume control, pressure control, and a pressure support trial. And then last but not least is going to be common ventilator alarms. The three to think about are high pressure, low pressure, and high respiratory rate. Again, these are kind of the basil foundational fundamental alarms. There's tons more uh which we talk about in a future video.
Um but high pressure alarm is essentially related to that peak pressure and the ventilator saying, "Hey, every time I'm trying to push this breath in, it is creating so much pressure, such a high pressure, I'm worried." And there's a quick checklist you can think of, right? One is, is something kinkedked? Okay, so is the tube kinkedked? Is the tubing kinkedked?
Is the patient biting on it? Um, is there a big kind of clog in the tube?
Cuz all that can lead to high pressure.
So, always run your circuit. Make sure there's no tube kinkedked tube. Um, after that, bronco spasm can do it. if those airways are spasming and closing down. Um, so think about has the patient got obstructive lung disease like COPD, do they need a breathing treatment? Do they have a bronco spasm from some medication they were given? Um, that can do it. Uh, certainly ventilator desynchrony, things like coughing or anything where that patient's kind of pushing against the breath that's being delivered can lead to high pressure alarms. And then just decreased lung compliance can do it too. Um, that would be both a high peak and a high plateau pressure. Um but the easily reversible things are is the tube kinkedked or is it clogged? Do they have bronco spasm?
Is there a ventilator desynchry going on? And if that's not the case, uh you get worried about kind of some inherent lung pathology leading to decreased lung compliance. Low pressure alarms are hopefully easier to deal with cuz this is almost always a manifestation of something wrong with the circuit. Okay, so run your circuit. Is there disconnection? Did something pop off where the tubing's no longer connected to the endotrachial tube? Did they bite through the endotrachial tube where there's a hole in it? Now, is the cuff ruptured? Right? These endotrachial tubes, most you probably know, are literal tube, little bevel at the bottom, and then they have a balloon, a cuff that you inflate, and they go in the patient's trachea. So, this cuff has to be inflated. So, it's touching the walls of the trachea. So, that air can't move past, you know, in or out of the trachea unless it goes through the endotrachial tube. But if that cuff is ruptured, they'll just lose all the volume that you pumped in through the ET tube and just come right back out around the tube. So, is there a cuff leak? And you can usually hear the patient, you know, speaking or gurgling or making vocalizations because they're able to pass air through their vocal cords.
Whereas, if the cuff's fully inflated, they can't pass air through their vocal cords, so you shouldn't be able to hear them. Or is there a circuit failure?
Right? Is the circuit itself have some kind of issue? And then high respiratory rate. uh that'll be an alarm you sometimes see and that's usually related to the patient pain, anxiety, inadequate sedation, but sometimes it can be from uh physiologic things like profound metabolic acidosis where they're trying to ramp up their tital volume and ventilation and all that jazz. Really high pressure and low pressure basics um are these here. Always run the circuit.
If there's one thing to take away, it's always run the circuit. All right? Make sure everything's connected. Make sure nothing's bitten, kinkedked, disconnected, fallen off, clogged. uh and after that it's a little easier to then think about the patient itself uh with what physiology could be going on leading to these things. So peak and plateau pressures these are two separate pressures that the ventilator measures and the reason they're separate is because they represent different physiologic findings right the measurement they are taking represents two distinctly separate things. The nice thing about peak and plateau pressures is it can give us a clue into the patient's physiology. In addition to that, we need to manage these pressures.
We don't want them to go too high because they can cause damage.
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Things like barot trauma um where the lung gets too distended, the alviola get too distended and as such they get damage. But to further understand some of these concepts, it really is helpful to dive into what these pressures are representing. So if we scroll down, we drew a you know quick and dirty version of the lungs, right? Right side, left side. This is the trachea, the main stem bronchi. And all these bronchi obviously break up into smaller and smaller, you know, bronchi into bronchioles. And eventually, if you were to zoom, you know, way in, this would end in kind of these balloon shaped alvoli, right? And these are kind of balloon shaped alvoli.
That's a really terrible drawing. Let's try it again. Um, terminal alvoli. And these are the little balloons that actually inflate and deflate for gas exchange. This blue thing here is an endotracheial tube, right? There's a plastic tube that goes into the trachea. You blow up a balloon here. So it forms a seal, right? And the ventilator delivers a breath into the endotracheial tube, right? That breath comes out of the end into the trachea.
It goes into both bronchi and then it waves its way into all the bronchi and bronchios into the alvoli and then it inflates the alvoli alvoli and expands the lung. Right? So this lung expands out after the breath is stopped on the ventilator. Right? The lung then contracts back in and the air goes the opposite way. So travels back out the main stem bronchi into the trachea into the endotrachial tube and then out the endotrachial tube towards the ventilator. Right? That's just the basics of how a breath is delivered on mechanical ventilation. So when we're evaluating a patient on the ventilator, let's just say you're prepping for uh you know rounds in the morning to present a patient uh to the attending uh intensivist. There's two pressures that we're interested in, right? The first is the peak pressure and the second is the plateau pressure. And these are both pressures that you can get off the ventilator. The peak pressure is often in the top right corner. It depends on the ventilator brand, but the top right corner and it's a pressure that you get with every single breath. Whereas the plateau pressure is something you actually have to test for. You have to do this inspatory hold maneuver that we'll talk more about to get the plateau pressure. So what are these? Starting with the peak pressure. The peak pressure is the pressure the ventilator is experiencing when it tries to push a breath into the lungs. So ponder that for a second. Right? This is a closed circuit, right? This endotrachial tube ends up coming out of the patient's mouth and then there's kind of tubing that weaves away onto the ventilator itself. But this is a closed circuit.
It's not open to the external environment. Right from the tubing to the endotrachial tube, there's this balloon that causes a seal into the lungs. So when this ventilator delivers a breath, the breath travels through the tubing through the endotrachial tube through the bronchi and into the lung tissue. And the pressure that is required to flow that breath through the tubing, the endotracheial tube, these airways and inflate the lung is the peak pressure. And that's why you get it with every single breath because when the ventilator pushes that breath in, it says, "Oh, this is the the peak pressure that I experienced while I was trying to inflate the lungs on that breath." So if we think about what that means, what that means is it's really a manifestation of the airway resistance and the alvolola resistance cuz those are the two things that are happening.
The breath is traveling through the airways and then it's inflating the alvoli. So the resistance of those airways and the resistance of those alvoli are what is going to create the pressure that ventilator experiences while it's trying to deliver a breath. Right?
Right? If we just make this more simplistic, let's just picture you had a a pump, right? Here's your pump. It's got a little nozzle at the end. And that nozzle is kind of plugged in to a pipe, right? And then there's a balloon on the end of that pipe.
The peak pressure would be the pressure it takes you to pump a breath through this pipe into the balloon and then start to inflate the balloon.
Right? If you're blowing into that, the amount of force you have to push in, the pressure required to flow the air through that pipe and inflate the balloon is the peak pressure.
And that is why it's a manifestation of the resistance of those airways to the breath flowing through them as well as the alvol avoli resistance as they try to inflate. So really the peak pressure is airway and alvoli resistance. Okay.
Now, as we talked about, it's detected when the breath is being delivered, right? Because it's an airway resistance. As the breath is flowing through these airways, that is when it detects the peak pressure. And do note that this is all in volume control. This is more of kind of an advanced topic um and probably outside the scope of this video, but there's different modes of mechanical ventilation. There's volume control, there's pressure control, there's SIMV, there's APV. There's all these different types of uh mechanical ventilation where you can deliver breaths differently. Um and peak pressure is really a discussion uh in this context for volume control which is the most common modality of mechanical ventilation. Okay. And the acceptable norm I put acceptable in quotes here um because acceptable is not necessarily normal. Acceptable is what we tolerate without getting very concerned and having to adjust the ventilator settings. And the acceptable peak pressure is less than 40 cm of water. So when you look at the ventilator and you get this reading, the peak pressure, you're going to get a reading that says X centimeters of water, right? Maybe it says 33 on that breath, 32 on the next breath, 34 on that breath. And these are all pressure measurements, right? In centimeters of water.
This is in contrast to the plateau pressure. The plateau pressure is detected with what we call an inspatory hold maneuver. So essentially what we're doing is we are pushing a breath in and then we are pausing the ventilator.
We're not letting any air out of the ventilator and we're not letting any more air go back into the lungs. So I'm going to erase all this and we can see if you can kind of draw it. I'm going to redraw. Right. The endotraal tube comes out the mouth. There's this tubing right out the mouth. There's this tubing. It goes onto the ventilator. And again this is a closed circuit. The idea that it's a closed circuit is really important. So when we deliver a breath in as we said the breath travels through the tubing through the endotrachial tube through the trachea the broncha into the bronchios and then it inflates the lungs right it goes to both sides obviously the plateau pressure is the pressure experienced when this breath is pushed in but not let back out and you pause the flow on the ventilator. There's no air flowing in or out. Right? So just picture it's essentially if you took your own breath in and then you just held it in your lungs. You're not letting any air in. You're not letting any air out. You can almost feel the pressure in your chest when you do that, right? Cuz your lungs are inflated and your lungs are tissue. So as the air is pushing those lungs out, the lungs are also pushing back in. They're trying to deflate back down. And if you're not letting any of that air escape, the plateau pressure is the pressure that the vent is feeling as those lungs try to deflate when we won't let them. It's an inspatory hold. So, as one might assume, then that plateau pressure is more representative of the lung compliance. The compliance being how easy those airways are to kind of uh distend out and collapse back in.
You can also think of it as kind of an alvolola resistance and lung compliance measurement. So if we think about what this is saying, the plateau pressure is actually sort of a part of the peak pressure, right? Because as we said, the peak pressure is when we push in air in and part of the peak pressure is airway resistance, but the other part of the peak pressure is we have to inflate those lungs, right? And if we're saying plateau pressure is lung compliance, the force that the lungs are trying to push back in on that breath, you can think of the peak pressure as airway resistance plus lung compliance plus the plateau pressure. The physiology there isn't perfect, but it's somewhat helpful in understanding these two things. Because when we think about peak and plateau pressure, we're going to talk about kind of highs and normals. An acceptable plateau pressure is less than 30, right?
And that's acceptable again cuz that's not necessarily normal. If you put a healthy person on a ventilator, um their peak and plateau pressure would be very low, right? Um so this is acceptable.
This is what we think is okay and will not induce a significant amount of barot trauma or overinflation or over distension of those alvoli.
So the difference between these two the peak and plateau pressure is important because if they are the same right if the peak equals the plateau pressure let's say the peak pressure is about 30 and then you do this inspatory hold and the plateau pressure and the inspatory hold is also 30 that is really saying that most of the pressure that you're seeing in the peak pressure is simply lung compliance and that there's not much airway resistance because lung compliance and airway resistance make up the peak pressure, right? Does that make sense? So, if the peak pressure is proportional to airway resistance, right? We'll just say airway R and lung compliance, lung C, and we're saying the plateau pressure is proportional to lung compliance.
If the peak equals the plat, that just means that all the peak pressure is lung compliance and the airway resistance is not contributing. That's in contrast if the peak pressure is greater than the plateau pressure. So let's just say the peak pressure is 50 and the plateau pressure is 20. Well, now this changes, right? Because if we're saying the plateau pressure is 20 and the peak is 50, we can essentially say that well, you know, 20 is related to lung compliance, but the other 30 left is airway resistance. And this can be helpful in understanding the pathophysiology going on because these two represent different things. So anytime the peak pressure is high, the second question is what's the plateau pressure? And if the plateau pressure equals the peak pressure, this is really a lung compliance problem.
If the peak pressure is greater than the plateau pressure, it's really an airway resistance problem.
And both could be high and it could be a both problem as well. But the differentiation between the two is important in deciding if it's an airway resistance problem or a lung compliance problem because airway resistance and lung compliance are going to represent different things. Right? So as we mentioned, let's say there's a high peak pressure and a high plateau pressure, right? So peak pressure is 30. Uh let's make it 50. Plateau pressure is 50.
That's very high. Well, remember what we said. If the peak and plateau equal each other, this is really just a lung compliance problem because the plateau pressure is lung compliance. And if the plateau equals the peak, that means airway resistance is not playing a big role because we said peak pressure is airway resistance and lung compliance.
So if they equal one another and plateau pressure is just lung compliance again means airway resistance isn't playing a role. So then we think about the things that cause an abnormal lung compliance.
And that is the pathophysiology that's leading to that high peak and high plateau pressure abnormalities in lung compliance. And those abnormalities easy way to think about it is kind of blood water plus inflammation fibrosis right blood being things like hemopticis if you have blood within the lung parankma itself. Mopsis isn't the disease, but it can cause by a number of things, right?
DAH, it can be from any type of arterial bleeding in the lung, right? So, blood in the lung can cause abnormal lung compliance, right? Cuz that blood gets in all those alvoli, clogs them up, doesn't allow them to distend um as uh they would normally, right? Water, so things like pulmonary edema, pade edema can cause an abnormal lung compliance.
Pus. Pus being infection. So things like pneumonia.
All right. Inflammation can be from anything. Let's say you have pneumminitis from maybe you aspirated and you have aspiration pneuminitis.
Maybe you're on a, you know, some type of chemotherapy agent that causes medication induced pneumminitis. So any inflammation in the lung. And then fibrosis, right? Fibrosis can cause the lungs to have decreased lung compliance.
Maybe it's like interstatial lung disease causing fibrosis. So if you remember these, that gets you through most of the things that can cause an abnormal lung compliance. The other thing is if you're not ventilating all the lung like you think you are, right? So if you intubate someone and you accidentally main stem them, right? Meaning that tracheal tube is actually going into just one of the main stems. That means you're not really ventilating this lung.
So you're trying to push all the tital volume into a single lung and that will lead to a high plateau pressure because that lung is exerting that much more you know downward pressure as it is trying to accept that full tidal volume.
Similarly if you had lung collapse of a certain area of lung that would cause higher plateau pressure as well because you're ventilating less lung than you think you are. Or if you have had a pneumthorax, a popped lung, let's say this lung's totally collapsed because there's a pneumthorax. Again, you're just ventilating one lung. And the monotital volume is the monot volume, right? Let's say you set the title volume at 500. That title volume is supposed to go into both of the lungs, right? And if it's only going into one of the lungs, so instead of getting 250 and 250, this lung's got a newumthorax and has collapsed down. That means now you're trying to put 500 cc's of title volume in that one lung and you're going to overextend it. You can think of it like a balloon again, right? If you're pushing 250 cc's into a balloon and then try to push 500, that pressure, that compliance that it's coming back down with um is going to be more robust.
Okay? So, if you're not ventilating both lungs the way you think you are, whether you main stem the intubation or have anthorax or have some degree of collapse, then otherwise this blood water plus inflammation fibrosis are the things that can cause abnormal lung compliance, which is the high peak and high plateau pressure. And this is just the echo, right? Because the peak pressure is something the ventilator just tells you on each breath. So if that peak pressure is high, the second question is always what's the plateau pressure? So do that inspatory hold.
It's a button on a ventilator. You hold the button and it pushes a breath in and then it holds it and it tells you what the plateau pressure is. Because the plateau pressure equals the peak pressure, then you know it's a lung compliance problem. Whereas if the plateau pressure is normal, it's low. So it does not equal the peak pressure. Cue this other one. We know it's an airway resistance problem. I feel like I'm repeating myself over and over, but this is just to really drive home the point, right? Peak pressure is both airway resistance and lung compliance because the peak pressure is the pressure the ventilator is experiencing when it's pushing a breath in through the airways and inflating the lungs. Whereas the plateau pressure is just a lung compliance problem because the plateau pressure is when the ventilator pushes a breath in and then holds. It doesn't let any gas flow back and forth, right? And then that is just a representation of the lung compliance. So if it's a high peak pressure to normal plateau pressure, you already know the lung compliance is normal, right? So you're taking this out of the peak pressure equation. So you know all that's left is airway resistance. So you have an airway resistance problem. And anytime you have an airway resistance problem, what you want to do is you want to trace the circuit. I call it cuz remember what we said. We said you have a ventilator and you have ventilator tubing and that tubing then attaches to the endotracheial tube, right? And that endotracheial tube is going into the lungs into the trachea. The endotrachial tube's got a balloon here and a balloon here and it uh is creating a closed circuit for your lungs. So if you have airway resistance that does not just mean airway that could be resistance in the endotrachial tube. It could be resistance in the tubing. So the first thing you always think about is endotracchial tube pathology. Is there a kink in the tubing? Is the patient biting the tubing? You know making it more smaller? Making it more small. Is the endotraal tube too small to start with? Is there mucus built up? Right?
Because all those things are going to increase airway resistance. I'm just going to draw an endotracheial tube.
Right? If you're trying to flow air through this endotracheial tube and let's say there's mucus built up on the side, you got big a big gloomba right there. Now, that air is trying to flow by a smaller area and that's going to lead to more resistance. Or let's say the patient's kind of biting down on the endotracheial tube. So instead of this nice flat surface, you have this huge kink in the side because the patient's biting down on it. Again, you're going to try have to try to flow more flow that air past a smaller surface and that's going to cause higher airway resistance, a higher peak pressure. So the first thing to do is to trace the circuit, trace the endotrachial tube. If the circuit and the endotrachial tube are all okay, well then you actually are having a true airway problem. And just like the endotrachial tube pathology, the problem with the airways could be mucus plugging, right? You get a mucus built up in one of the airways just like you could in the endotrachial tube. Now you're trying to push air past mucus built up in the airway. Smaller area to push it through. Higher airway resistance. You also get a bronco spasming of the airways itself. Maybe the patient has COPD or they have asthma, right? And those bronos spasms is when those bronchi kind of spasm down, right? Creates smaller amount of area to flow that air through. higher airway resistance, maybe there's a foreign body in the area, maybe the patient has ventilator desynchrony, they're not being cooperative with that breath and they're kind of pushing back on it. All those things can cause high airway resistance. So again, high peak pressure. Second question is what is their plateau? If it's a normal plateau pressure, then you know the lung compliance is normal and you have an airway resistance problem. If it's a high peak pressure and a high plateau pressure, then you know it's a lung compliance problem and not an airway resistance problem, right? And that similarity between the two is if they're within about 5 cm of water. Now, if they are both high, right? Let's say the peak pressure is 60 and the plateau pressure is 40. They're still different enough where you have an airway resistance problem, but you also have a lung compliance problem because they're both high, right? We said a acceptable plateau pressure is less than 30 and we said an acceptable peak pressure is less than 40. So they're both high but the peak is higher than the plateau. So we know that you have both a lung compliance problem and an airway resistance problem.
All right. So if you think about it that way, it sticks a little bit better, I think. And then last but not least is just the scalers. If you don't have an interest in this or don't have the background, um this certainly isn't that important. But this is a pressure versus time scaler. This is something that shows up on the front of the ventilator screen. And remember, this is in volume control. And you can see here that this is zero for the pressure.
The peak pressure is going to be the peak pressure that the ventilator experiences when it's pushing a breath in. Right? So, this is where it's starting to push a breath in and then it gets to this peak. And this is what the ventilator is putting on the side of it.
Right? Let's This is 30. The peak pressure is 30.
The plate toe pressure though, as we said, is a maneuver you have to do. So, I wonder if I take a marker. Uh, let's just I'm just going to draw over this so we can draw something fresh.
Just pretend like it's the same color as the other ones. Um, so if you do an inspatory hold, right, a patient takes a breath, they have the peak pressure, and then you have an inspatory hold. The ventilator will go like this. This is when it's holding the breath, and then you let go, goes back down to zero, and the patient can take their normal breath again. Okay. Uh this here is the plateau pressure right this portion of the inspatory hold. So that is literally on the scaler will give you a pressure you know if this is 30 let's say maybe this is just 20 nice normal plateau pressure and it will kick this out on the screen too. There will be a little area that says plat and then it'll give you a number like 20. But you have to do the inspatory hold right you have to hit the button and our respatory therapist will do this. Um certainly you shouldn't be doing this too much on the ventilator without the respatory therapist especially if you're early on in your training. Um but you have to do an inspatory hold to get the plateau pressure whereas the peak pressure is just that peak pressure at the end of each breath and that's an automatic thing the ventilator reads. Um and no further ado spontaneous breathing trials. So what are spontaneous breathing trials? Well a spontaneous breathing trial as many of us know is kind of the gold standard bedside assessment tool to determine whether a patient can safely be liberated from mechanical ventilation. Right? Right?
So, it's an evaluation on the patient's ability to breathe without significant ventilatory support, right? A way to simulate extated conditions um as a way to know or understand if a patient might be ready to be liberated from mechanical ventilation. So, the goal here is we're trying to identify the readiness for extabation. A really important thing, obviously, you don't want to leave anybody on the ventilator longer than you have to. Uh there's certainly um complications that can come with being on mechanical ventilation ranging from just ventilator associated lung injury to ventilator associated pneumonia uh sedation, delirium, all that stuff. So getting patients liberated from mechanical ventilation is critically important. One of kind of the cornerstones of critical care medicine.
Um so the goal is to identify who's ready to come off the vent. Uh timing for spontaneous breathing trials in general, and we'll dive more into the details on this, but in general, we're usually doing this after improvement in the underlying illness, right? What caused them to be intubated and have we improved that enough to no longer need the ventilator? Right? If the cause that they was that they were completely abundant and unresponsive, are they awake now? If the cause was they had profound hypoxmia from pneumonia, is their pneumonia improving? Right? All these things make sense. So, have we addressed the underlying cause in a way in which we think they might not might not need mechanical ventilation anymore?
Humanic stability is another one.
There's lots of gray to humanic stability. Um the old adage used to be that you need to be totally stable off vasopressors the whole gambit. Now we're starting to understand that you know you probably don't have to be totally off vasopressors. How much vasopressors are reasonable to come off the vent? Still an unanswered question. But some degree of hemic stability or maybe the more appropriate way to contextualize it would be hemodynamic improvement. You know, if you were on 30 micrograms per minute of norepinephrine and vasop prein and that vasop prein is now off and your norepinephrine is down to, you know, five or eight micrograms per minute, maybe that's a patient who even though they're still in vasopressors, uh, you could consider liberating from the ventilator. Um, this is not medical advice, never is. You should certainly verify all this before acting on it. Uh we have disclaimers in the episode description and at the end of the episode, but anecdotally our practice pattern um we're okay liberating patients from mechanical ventilation who are still on vasopressors assuming we're improving their underlying illness. And then the last thing is adequate oxygenation and ventilation obviously.
So you know I think many people and we'll go into this more many people would put a people less than 10 and an FiO2 of less than 60% as kind of two oxygenation goals before you can put someone in a spontaneous breathing trial. Some people are more particular, right? Some people talk about uh people less than eight and FI2 of 40%. Um some people maybe are a little more aggressive. Anecdotally, again, uh we use this PEP less than 10 FO2 less than 60% personally. And then typical duration of these spontaneous breathing trials, 30 to 120 minutes is probably reasonable. Um some of the trials used 30 minutes before they exabated patients. Other people use a little bit of longer time frames. Um so 30 to 120 minutes. Again, lots of gray here, which is good. You know, that's why we're doing this video. So you can kind of hear a little bit of uh uh insight and practice patterns on that. So how do we actually do the spontaneous breathing trial? Well, it would be easy if there's just one way to do it, but there's not.
So the first thing when you're talking about it is do they meet some of those prerequisites we mentioned, right? F2 less than 60%, PEP less than 10 depending on who you are. Uh might vary per patient, but are they oxygenating well enough without significant ventilator support? Are they ventilating right? Are they not hypercapnic? Uh do they not have acute hypercapnea where they're able to ventilate well enough on their own? Do they have some degree of hemodynamic stability or hemodynamic improvement? Do they have an adequate mental status? Can they protect their airway? If you were to exabate them, are they able to protect their airway? Do they have a cough? Are they awake enough um to spontaneously ventilate on their own? Are they strong enough to do that? These are some of the soft indicators that someone is ready to come off the vent potentially. And then the last thing is secretions or can they manage their own secretions? And this is tough because a lot of times we're like, oh, they have uh significant secretions.
What do you do with that? Gosh, we don't I don't we don't know what to do with that. You know, if they have a strong cough, hopefully they can mobilize those secretions on their own. If they have a weak cough and lots of secretions, maybe that's someone you give a little more time on the vent. um tough to say, but secretions is something that you should at least evaluate for um and think about before you liberate someone from mechanical ventilation. And then the other thing like anticipated procedures, are they going to the operating room in 5 hours? If so, maybe you leave them on the ventilator. Do they need a MRI of their brain and a whole spine in 2 hours? You know, that's a long test.
Maybe leave them on the ventilator. So, just kind of anticipate a clinical course is another thing to think about.
So, if you've decided that yes, they meet the prerequisites and yes, you want to do a spontaneous breathing trial, well, what the heck do you do then? What are the different methods to do a spontaneous breathing trial? We're going to talk about the two less common methods and then we'll talk about the more common mainstream method. The two less common methods are a Tpiece trial and a CPAP trial. And I want to be very specific with the verbiage here because at times people call a pressure support trial a CPAP trial. And that's not necessarily true and we'll get into that more. But starting with the Tpiece trial, this used to be much more mainstream. Uh we personally don't really do Tpiece trials. We've maybe done it once or twice for kind of weird unique situations, but in general, we don't do TP trials. And what a TP trial is is you literally take someone off of the ventilator and you let them breathe through their endotracchial tube just hooked up to supplemental oxygen.
There's no ventilator assistance at all.
There's no PEEP, there's no inspatory pressure, there's nothing. They're breathing through the endotrachial tube hooked up to wall oxygen. And there's some trial data to suggest that this isn't necessarily the best modality to use for a spontaneous breathing trial.
Um, in fact, outcomes were worse. And again, we'll talk about that trial in a second. But it makes sense that outcomes might be worse, right? Because you essentially have a straw aka that endotrachial tube going into someone's airway and you're taking away all support and just having that patient try to breathe through that straw. So they don't have any PEEP which means they can get alvolar collapse and adalcttois right you don't have any inspatory pressure that inspatory pressure the pressure that is delivered during a breath kind of gets over the resistance of the endotrachial tube try just breathing through a straw that's hard right now imagine being on a ventilator being taken off that ventilator and being asked to breathe through that straw um so tie trials uh are not mainstream anymore uh and for good reason which we'll talk about the other one we wanted to talk about that isn't commonly used is an actual CPAP trial and we sometimes call pressure support trials CPAP trials but an actual CPAP trial is that you just leave the patient on PEEP but you take away all inspatory pressure. So what this means is you know the patient's still on a PEEP of five but otherwise they're just breathing through the endotracchial tube themselves. There's no inspatory assistance. So you still run into the resistance of that endotracheial tube because every time the patient takes a breath, they have to suck air through that endotracheial tube without any assistance. There's still increased airway. There's still increased resistance trying to suck air through that endotracheial tube. And as a comparison to help that make sense, that gets into the more common approach to vent liberation and spontaneous breathing trials, which is a pressure support trial using pressure support ventilation. And what this is, this is the most common way we do spontaneous breathing trials in ICU pressure support trials. And we essentially leave the ventilator providing a PEEP just like it would for the CPAP trial, right? A positive endexpatory pressure. And usually that's minimal. Usually that's five, but again, some people talk about less than 10, some people talk about less than eight, but five would be minimal. We leave a little bit of PEEP.
And then we actually provide some pressure support, some inspatory pressure support. Anywhere in the realm of five to eight above the PEEP, you know, five being minimal, eight being a little bit higher, but anything greater than eight is a little more significant in terms of support, which I'll talk more about in a minute, but just to lay this out. So, what happens is the patient's on the vent, you switch the mode of the ventilator to pressure support, and that ventilator does not deliver any breaths except when the patient triggers it. So, if the patient doesn't take any breaths on their own, the vent doesn't give them any breaths.
they're completely apnic until you eventually get to the apnea alarm in which case the ventilator then has a backup mode that kicks in. But when the patient goes to take a breath, the ventilator senses that and it delivers a certain amount of inspatory pressure, that pressure support, 5 mm of mercury, 7 mm of mercury, some type of inspatory pressure. And the thought there is it's just enough inspatory pressure to get over the resistance of the endotracheial tube. So it's not intended to provide actual inspatory support. It's just intended to provide enough pressure to get past that resistance of the endotrachial tube. And then obviously you leave some peep on like we talked about. And that is the most common way we do spontaneous breathing trials. This pressure support trial. And as you can see then the difference between the pressure support trial and a CPAP trial is the CPAP trial just has PEEP. It doesn't have any of that inspatory support. And a Tpiece trial doesn't have PEEP or inspatory support. You're just trying to suck air through that ET tube.
So if we go into one of the trials that looked at spun uh pressure support trials versus Tpiece trials, it's a trial by uh Phil at all 2016 published in JAMAMA and it was a multic-center RCT had about a thousand patients in it. And they compared pressure support ventilation where you have that inspatory pressure and a PEEP, right?
just enough inspatory pressure to get over the resistance of the endotrachial tube. Somewhere around 5 to 8 cm of water, millimeters of mercury and minimal PEEP somewhere between 5 and 8 um just to prevent adalcttois versus a Tpiece trial. Remember we said TP trial means you just take them off the ventilator and attach their ET tube to supplemental oxygen. And what they found in this was that pressure support trials were associated with lower extation failure rates than the Tpiece trial, especially in high-risisk patients, older folks, COPD, cardiac disease. And that's really interesting, right? Cuz it's saying that in patients you did the Tpiece trial on, you were more likely to have extation failure. And you start to wonder is that because you took away the PEEP and everything and that patient got adalcttois and lowbar collapse and all that jazz and then you extabated them and they had more trouble remaining extabated than the pressure support trial where you have some inspatory pressure and some PEEP still there to maintain recruitment get over that endotrachial tube resistance. So from this trial, it supported the use of pressure support trials uh rather than TPS trials as the most physiologically relevant patientfriendly SPT method, which is why not many people do TP trials anymore. All right. So going into pressure support trials since that's kind of the main way in which we try to do spontaneous breathing trials. Um this is the most common modern approach and as we talked about the endotracheial tube adds resistance when you try to breathe through it. So a small amount of inspatory pressure helps co overcome that resistance which is actually more similar to kind of that normal physiologic airway after you activate them. Right?
When you estabate them, you're not giving them a straw to breathe through.
You're just letting them breathe normally. Um and a pressure support trial mimics that extabated state better. Uh typical settings as we talked about is an inspatory pressure also known as a pressure support of 5 to 8 and a PEEP of you know somewhere around five although some people would say less than 10 some people would say less than 8 and an FO2 of less than 60% although again some people would say less than 50 or even 40 or less. So some variability in the PEEP and FiO2. Um but do note that this pressure support this inspatory pressure 5 to 8 cm if you start to increase that inspatory pressure higher than that you're no longer just overcoming the resistance of the endotrachial tube you're actually providing them with significant inspatory pressure support and that's almost like pressure control a mode the pressure control mode of ventilation where you're providing an inspatory pressure to the patient to help them breathe. So you really want to make sure this pressure support is minimal. If you're starting to get a pressure support at 10 or 12 or 14, that is essentially pressure control. Um obviously you are still in a pressure support mode, but the amount of inspatory pressure you're providing is significant. That is not mimicking, you know, just enough inspatory pressure to get over the resistance that tracheal tube. That's significant support. So this minimal pressure support number of 5 to 8 inspatory pressure, 5 to 8 millm mercury is critical when you're doing these pressure support trials.
All right. How to tell if a patient is doing well? Well, the first thing in you should look at is the vital signs, right? Have they gotten super tacicartic all of a sudden because they're an extremist, heart rate of 120, 140?
Obviously, they're not doing well. Then, have they gotten hypotensive or hypertensive? Also, maybe an indication that they're having trouble. Now, it's tough, right? Is it because of the wean and sedation? Is because they're uncomfortable on the ventilator? All these things play a role. Um but vital sign derangements do imply that patients are much higher risk once you extabate them. Can they still oxygenate? Right?
Are they maintaining their SPO2 above 90? If you send a gas a PF ratio greater than 200, but really the the message here is are they still able to oxygenate while on a pressure support trial on the vent? Because if they're getting hypoxmic, that might indicate they're not ready to be liberated from the ventilator. Same thing with ventilation.
Are they still able to ventilate adequately? They're not getting more hypercapnic. Some people routinely send gases when patients are on pressure support trials. You know, we don't tend to do that unless we have something we're worried about. Um, sometimes we'll leave them on end title and make sure there isn't some big jump in their end title CO2 in the monitor. Um, but obviously user preference on that one.
But are they able to adequately oxygenate and ventilate? And then is their mental status still stable? Did you put on pressure support and now all a sudden they're obtinant unresponsive?
Maybe because they're hypercapnic, right? You their mental status has to remain stable. And then do they have a tolerable work of breathing? They're not diaphoretic. They're not using accessory muscles. They're not belly breathing.
They're not super tic tacipnic, right?
Do they have a tolerable and stable work of breathing is the other critical thing. And this is all very subjective to a degree. You're looking at the patient, you're like, what do they look like? How are they breathing? Do they look comfortable? Etc., etc. When we try to make this process more objective, one of the common markers people talk about is something called the rapid shallow breathing index, the RSBI. Some people call it the risby. Um, and the rapid shallow breathing index is a math equation. It is the respiratory rate divided by the title volume in lers.
Okay? So, respiratory rate divided by title volume in liters.
And when people have studied this, if we think about what this means, it essentially means that they're breathing comfortably so the respiratory rate is reasonably low and that they're pulling high enough title volumes because you want the RSBI low. Less than 105 has been a good predictor of successful extation.
Now, we'll go into the trial, one of the big trials on the RSBI cuz it's not perfect. So, you should always use it, you know, with your clinical judgment.
that it's not an end- all beall, but it's maybe an easy place to start, especially for trainee or people early in the field who kind of want something more graspable to help them understand if a patient can be liberated. The RSBI is a reasonable place to start, but it's not the end- all beall by any means.
Okay, so respiratory rate divided by title volume in liters. So, the one of the newer trials on this was from 2016.
I don't know how to pronounce their name, apologies, but Tanios at L published in critical care medicine and it was a prospective multic-center observational study. Okay, so this is not a randomized control trial and it looked at the rapid shallow breathing index in ICUs and it was after there was this trial in 1991 by Yang and Tobin, which was kind of the OG RSBI trial that showed a really good sensitivity and predictive value of the RSBI. But then Tio atl went and tried to see if they could validate this and they looked at about 900 adult ICU patients. It was mixed medical surgical trauma and neuroICUs. They looked at all mechanically ventilated patients deemed ready for weaning. Right? So the patients that met those other criteria, hemodynamic stability, oxygenating appropriately, ventilating appropriately, mental status improving, etc., etc. And the primary outcome was extation success versus failure at 48 hours. So did they need to be reintubated by the 48 hour mark? and they use the RSBI cutoff of less than 105. And the results here were that those who had an RSBI less than 105 still it was associated with a higher probability of extation success, but it was it was fairly modest in terms of the results compared to the original 1991 trial. There are still many patients with an RSBI of less than 105 that failed extation and some patients with an RSBI of greater than 105 that had successful extations. So all this to say, you know, that this is one marker amongst many markers you should be thinking about when you're thinking about liberating a patient from mechanical ventilation. As we said, a good place to start, but not the end all be all. You know, do note that this was an observational trial. It was not randomized. They looked only at an RBI less than 105, not like multiple different RSBIS. Um, and there are some things you couldn't really account for.
Airway protection, secretion burden, all that kind of stuff. um which obviously can affect extation failures. So bottom line here RSBI's maybe you know a screening tool or just one piece of data but it's predictive accuracy is not absolute uh and you use the clinical your clinical judgment and some of these other uh kind of clinical assessment strategies in addition to the RSBI to help guide you. So with that being said, key considerations um signs of failure would be severe tacipnia, hypoxmia, tacocardia, hypertension or hypotension, agitation, diapheresis, right? Anything that looks like there's increased work of breathing. Um trial duration that we said is 30 to 120 minutes. Um variability there. Failure is usually declared earlier if there's intolerance.
And the big thing here, and we probably should have said this earlier, is there's incredibly robust evidence that daily spontaneous breathing trials and sedation interrupts up interruptions reduce ventilator days and improve mortality. So all patients, we cannot stress it enough, all patients that qualify should have daily SPT, spontaneous breathing trials, and SAT, sedation vacations. every single patient that improves mortality and reduces ventilator days. Absolutely it does. This should happen for all patients.
All right, to end here, we'll have some practice questions, but we just put a table in here. And you know, every one of these study guides will be on our Patreon page, which is in the video des uh episode description, and we upload all of our study guides, practice questions, ad free videos, uh medad posts, you know, discussions, all that good stuff. So, definitely check that out. We'd love for you to join or hop on board. But yeah, the study guide will be on there if you're interested in accessing the study guide. Uh because this table here is kind of a comparison of spontaneous breathing trial methods including the T-piece trial, pressure support trial, and CPAP trial. And just going with setup, right? For a Tpiece trial, the patient's literally disconnected from the ventilator and hooked up to humidified oxygen. For the pressure support trial, the patient remains on an inspatory pressure and a PEEP. And for a CPAP trial, the patient just remains on PEEP. So from a support standpoint, a TPS trial, there's no support. There's no PEEP, no inspatory pressure. For a pressure support trial, there's inspatory support and PEEP. And then for a CPEP trial, there's just PEEP. There's no inspatory support. So the physiology here for Tpiece trial is, you know, post extabation conditions, people will say a TP trial is closest.
We actually disagree with this because it doesn't account for the resistance of the endotracheial tube. For a pressure support trial, it accounts for tube resistance. So, it's arguably the most realistic. And then for a CPAP trial, you know, it just has PEEP. It's maybe like in the middle there somewhere.
Advantages for TP trial, it's simple, no ventilators needed, but the patient was already on a ventilator. So, like, is that a real advantage? Probably not. Uh pressure support trial, it's most commonly used. It's most comfortable for patients. It's easy monitoring and there's the most evidence behind it. And then for a CPEP trial, you at least maintain alvolar recruitment and prevent adalcttois because they're on PEEP.
Although you don't prevent any inspatory pressure to get over that endotracial tube resistance.
Disadvantages for TPR increased work of breathing, overestimates failure, not supported by the evidence, requires disconnection from the ventilator.
disadvantages to a pressure support trial is, you know, it may underestimate extation difficulty because you do get a little inspatory pressure support. Um although that theoretically if it's low enough should just be enough to get over the resistance the endotrachial tube.
And then CPAP trials disadvantages are they're less uh well validated. Um people just haven't looked at them as much. Common use we would say Tpiece trials much less commonly used today.
Pressure support trials widely used.
CPAP trials not commonly used and then evidence um there's most evidence supporting pressure support trials uh much less evidence supporting CPAP or TPE trials. All right, let's get into some practice questions. If you have not um participated in practice questions one of our episodes before the structure is we'll read the question, we'll read the answer options and then we actually just go right into the answer. So if you need more time to think about it, just pause the episode because we're going to jump right into the answer. So question one, beginner, there will be three questions. Which of the following is the primary purpose of spontaneous breathing trial? A to reduce sedation requirements. B to evaluate readiness for extation. C to measure lung compliance or D to prevent ventilator associated pneumonia. Pause here if you need to. The answer is B to evaluate readiness for extation. Right? Every patient should be having a spontaneous breathing trial every day to determine if they might be ready for extation. All right. Question number two, intermediate. A patient is on a pressure support of 5 cm of water. a PEP of 5 and Fio2 of 40% during their spontaneous breathing trial. After 1 minute, their respiratory rate is 30 and their title volume is 300. What is their RSBI and does it suggest success or failure? So, we'll do the math with you here. Um, so RSBI, rapid shallow breathing index equals respiratory rate divided by title volume in liters. This patient's respiratory rate was 30 and their title volume was 300 milliliters which is going to be.3 L. 30 divided by.3 hopefully is 120 maybe. Uh-oh. Did we do our math wrong? Good thing we have a calculator right next to us on our phones. 30 /.3 is 100. I actually think we might have done our math wrong for the answer. So, it should be 100, which is B. Less than 105 is most likely success, but it's kind of right on the border. But did we put uh Yeah, we did. We put C, but that's not true. We just did our math wrong. Um, good thing we got to explore that together. So, the correct answer is B uh 100, which is borderline. It still meets, right? Less than 105 is that magic number that they used in these RSBI studies. But as we talked about many times, this is just a single data point. It shouldn't be totally dependent on. And then last question, question three. Advanced in randomized control trials, which approach was shown to shorten time to ext? A. Intermittent mandatory ventilation weaning. B.
Pressure support ventilation with gradual reduction. C. Daily SPTs with prompt extation if tolerated. D. Routine use of CPAP trials for 24 hours. Correct answer is B. Daily SPTs with prompt extation. This absolutely is the thing that you should all be focusing on. in your ICUs. Give Oh, give patients um gosh, we are striking out here. We circled the wrong answer on the video.
Give patients daily SBTs, right? SBT SAT for every patient every single day that meets criteria that improves outcomes.
Absolutely. No further ado, how to present mechanical ventilation on rounds. So the start of this tends to be with uh an organization or a structure um to how you want to present the different parts of relevant data related to mechanical ventilation. So you have a patient and they are intubated. Okay, maybe is it a sad face or happy face? I guess we'll say it's a sad face. And you are the one pre-rounding on them. You need to collect certain data. And the data you need to collect on pre-rounds is actually a lot. And this is this is a robust, right? There's a comprehensive look. Not saying you got to present this on every patient every time on rounds, but this is kind of a comprehensive approach. And the data you really need is you need to know their mode of ventilation. Are they on volume control?
Are they on pressure control? Are they on some different like pressure support?
Maybe they're on an SPT trial. You need to know their ventilator settings. Uh particularly things like PEEP, FiO2. All right. Is it volume control? What's their title volume? or are they on pressure control? What's their inspiratory pressure? You need to know their respiratory rate. Depending on their physiology, sometimes you need to know things like I to time. We're going to talk more about all this. Then you do need to know their peak and plateau pressures. Uh recent arterial blood gases, what your goals are is important to know uh and have recent chest X-ray findings and then what you want to do with all that great data you collected.
All right, so that's kind of the basic foundations of data collection. These are the things we're going to be talking about.
uh in terms of how to collect the data, how to think about it, and how to present it. So, if you start with number one, mode of ventilation, the common modes to know, and we've talked about this in the past, we have tons of videos on mechanical ventilation uh linked in our mechanical ventilation playlist. So, check those out if this is confusing, but the common modes to know are volume control and pressure control. These are the two main modes of mechanical ventilation that we use. Pressure support is important to think about too if they're on it, right? spontaneous breathing trial patients when you're trying to liberate them from mechanical ventilation often have a pressure support trial. SIMV people still talk about but this is not commonly used. So we're going to cross it off there. So the two main ones with kind of a third possible that you need to know are volume control, pressure control or pressure support. So if you're on rounds it's important to start with you know patient is on volume control or patient is on pressure control or patient is on pressure support trial. Right? So that is number one mode of ventilation.
Number two is going to be ventilator settings. Okay. And there is somewhat an order to this madness. People probably don't really care too much about the order, but there is uh some degree of formality to the order, which we'll talk about. But ventilator settings are the next thing to know. So, you already identified maybe your patient's on volume control. They're on AC VC. All right. Now, what settings are they on?
And the settings to think about are respiratory rate, title volume. if they're on pressure control instead of title volume, you need to know your inspatory pressure and then your FiO2, your PEEP, and I to E ratio sometimes, which we'll talk more about in a second.
Okay. Um, but when you're thinking about this on rounds, usually we have respiratory rate followed by title volume followed by FiO2 followed by PEEP. Okay, when you do present their title volume if you want bonus points, you can say what cc's per kg of ideal body weight it is. So this might look like you know patient X is on ACVC uh ventilator settings are 18 450 which is about 60 cc's per kg of their ideal body weight to 40% PEEP of 8. If someone has obstructive lung disease or kind of a deranged ID ratio, normal being about 1:2, it is important to say that because these things can get lost track of sometimes. So let's say they're on an ID ratio of 1 to4 cuz they have a bad COPD exacerbation. You can then add that ID ratio at the end, right? So patient X is uh on ACVC uh mechanical ventilator settings are 18450 which about 60 cc's per kg of a do body weight FI2 40% PEEP of 8. their ID ratio is still 1:3 um for their obstructive lung disease. Okay, if you have a attending or someone who's thinking about stuff and they're really quick, sometimes they don't even want you to label things. They just want you to say 18, 450, 40% and uh just in this order rather than saying peep of 8, Fio2 of X, title volume of X, and resto rate of X, but that's somewhat person dependent. Uh it's always easier to start by saying what things are. Uh and you can always take out those labels if if that's what people prefer, right? So maybe say patient X is on uh volume control with respiratory rate of 18, title volume of 450. That's about 6 cc's per kg of ideal body weight FI2 40% PEEP of 8. Their ID ratio still 1:3.
All right, you still with me? So we've done one so far mode of ventilation.
We've done two ventilator settings.
Let's keep stacking on. So peak and plateau pressures, this is the next thing. And this is starting to get next level. A lot of people can do one and two with the mode of ventilation and settings, but once we get to three, this is where we really start to uh uh impress and start to really understand things a little bit better, which is important, too. Um, and the pressures you're most interested in are going to be the peak pressure and the plateau pressure. And remember, the peak pressure and plateau pressures, this is really for volume control settings. uh you can't really get um it's not easy to get accurate numbers if someone's on pressure controls. This is for volume control settings. All right. The peak pressure differs with each breath and it's usually shown on the ventilator screen somewhere. So every time a breath's pumped in, uh often it might be in the top right corner. You got kind of your ventilator screen. You might get your peak pressure up in this top right corner, but it depends on the brand of ventilator that you have. Uh but a range is okay. Let's say the peak pressures have been kind of 30 to 40. All right, write that down and record that. Then their plateau pressure, their plateau pressure, you actually have to do an inspatory hold maneuver. Not that we are suggesting you should go do a bunch of stuff on the ventilator. Certainly make sure you're following whatever protocols your institution has. Um, this is often recorded in the chart by respatory therapy every so often, but you can do a bed site, too. It's really easy. Just do an inspiratory hold. Okay? And then when you do that inspiratory hold, it'll usually pop up somewhere on the ventilator screen as plateau pressure.
All right? And that's a singular number.
Let's just say the plateau pressure is 24. Okay. The last uh kind of pressure that can be important to document uh and to present and this is really next level is the driving pressure and we don't want to go into what exactly driving pressure is but it is a surrogate for possible kind of optimal PEEP and the goal is less than 15. All right. The goal plateau pressure is less than 30. the goal peak pressure. There's some variability here, but less than 40 is probably a reasonable number. So, if we were to present three peak and plateau pressures, you know, you might say something like peak pressures have range from 30 to 40. Plateau pressure this morning was 28 and the driving pressure is 14 or the driving pressure is 20. All right? And if you were to connect all those now, we got one which is mode of ventilation. We have two which is settings. And we have three which is pressure. And you might say something like patient X is on volume control. Their current settings are a respiratory rate of 18 tit volume of 450 which is about 6 cc's per kg of ideal body with their FA to 40% is their peep of 8. Their ID ratio is still 1:3.
Their peak pressurees range this morning from 30 to 40. Their plateau pressure when I checked this morning was 28 and their driving pressure is 14.
All right, things are getting a little more tricky, but yes, peak and plateau pressures are the next things to add on.
And then driving pressure is a nice bonus. This is particularly helpful if you have a patient in ARDS. Okay. All right. Step number four. Now, we're going to add on the arterial blood gas.
Now, this is something that should be reported in our humble opinion when you're presenting mechanical ventilation. uh it might come up in your plan elsewhere too, but when you're presenting data, the most recent AGS important to know. You don't necessarily need an AG all the time for each patient, but the most recent AVG if it's within the last 24 hours is important to present. And typically, you would present the pH, the PAC2, right, which is the partial pressure dissolved carbon dioxide, the PAO2 or the partial pressure of dissolved oxygen. And the bicarbonate comes on the AVG2. We personally don't usually present the bicarbonate but you certainly can. And the sp2 in the pulse socks uh can be relevant. You could present that too if you would like. The order in which these are presented is usually pH followed by pa2 followed by pao2. And if you do bicarbonate bicarbonates at the end although again we don't tend to do bicarbonate. Um so you might say if you're presenting the ABG is most recent ABG was from 3 hours ago. The pH was 7.34. or PA2 is 48 or PAO2 is 82. Uh if you really want to go quick and you want to take away the labels, you just got to make sure that everybody knows what you're talking about. But you could say something like the most recent arterial blood gas was done 3 hours ago. It demonstrated 7.3448 and 82 uh would be a reasonable way to present that too as long as everybody's on the same page which not everybody always is. All right. When you are interpreting this, just remember that the PA2 is a marker of ventilation, which is respiratory rate and tidal volume. The PA AO2 is a marker of oxygenation, which is usually PEEP and FiO2. And we'll talk a little bit more about that. So, we're going to stack all these together. Hopefully, we don't start to forget things. We certainly might. Um, but you can say patient X is on volume control. Uh, ventilator settings are 18450, which is about 60 cc's per kg of ideal body weight. um 40% and 8. Their ID ratio is still 1:3.
Their most recent peak pressures this morning were between 30 and 40. Plateau pressure was 28 and driving pressure was 14. Their arterial blood gas from 3 hours ago it was 7.34 48 and 82.
All right, we're getting more complex.
I'm sure at some point we're going to have to edit out how we forgot some of the details around the patient. Let's go to step five. This is oxygenation and ventilation goals. And this is not necessarily something you have to explicitly present because the team probably knows this. But um depending on the clinical scenario, sometimes you do want to present this. You can briefly state targets. Um sometimes you're doing things like permissive hypercapnea.
Sometimes you're allowing some degree of kind of lower oxygen saturation.
Sometimes you're doing different lung protective strategies. So if you're going to present the goals, it's easy to do it after the arterial blood gas. Um, you could say things like achieving desired oxygenation with an SPO2 greater than 92%. Um, and we are allowing for permissive hypercapnea in the setting of ARDS. Um, again, this is somewhat of an optional step. Um, but it can be useful depending on the clinical scenario if you're not necessarily targeting the most standard um, endpoints. But we'll leave that out of our long presentation.
Uh, and then we'll go to step six and then we'll do five and six together. So septics is the most recent chest X-ray.
Many patients get who are on ventilators get chest X-rays every day. You don't necessarily have to, but that's a discussion for another time. People have differing opinions on that. But if you are getting chest X-rays, it's really important to present the endotrachial tube location, how many centimeters above the corina it is. Right? The corina is where that trachea um um by sex into the right and left bronchi.
So that is important. Also any kind of infiltrates, consolidations at alacttois, certainly pneumthoroses um are all important to present to. So you could say something like most recent chest X-ray was from yesterday evening at 11 p.m. Then tubes 4 cm above the corina. There were bilateral infiltrates consistent with pulmonary edema. And then it's always really helpful to include a comparison to the previous. So you could say something like this looks to be improving as compared to the X-ray from two days ago. So now let's see we got step one which was mode. We have step two which was settings. We had step three which was pressures. Step four hopefully we're not making everybody not want to do critical care medicine. Step four was AVG. Step five was kind of targets for oxygenation and ventilation.
Step six is chest X-ray findings. So let's see if we were to do all this.
You'd say patient X is on volume control. Their current ventilator settings are a respiratory rate of 18 f of 450 which is about 60 cc's per kg of ideal body weight to 40% PEEP of 8.
Their ID ratio is still 1 to3. Their inspatory pressures or peak pressures this morning uh range from 30 to 40.
Their last plateau pressure was 28 with a driving pressure of 14. They had an arterial blood gas from 2 hours ago. It demonstrated uh pH 7.34 pa2 of 48 pa2 of 70. Um they are currently achieving their targets for ventilation and sending a permissive hypercapnea as well as oxygenation. Most recent chest X-ray was from 24 hours ago. that trachial tube was 3 centimeters above the corina did demonstrate improving um bilateral infiltrates that we thought was pulmonary edema as compared to the chest x-ray done uh preceding that.
All right. Uh hopefully hopefully we didn't miss any parts of that when we were saying it out loud. We didn't uh prep these ahead of time, so we're doing them in real time. And last but not least is the clinical assessments and plan. This is where you go from just reciting the information to actually interpreting it. This is the wrap-up interpretation. Now, sometimes this is best done in the plan. Okay? When you're presenting on ICU rounds, usually you present the data first, then you go into a plan. So, our practice pattern is to put all this in the plan. And if you're going to do that, just say once you're done talking about the ventilator, talk, we'll talk about adjustments in, you know, if you're doing a headto toe presentation, so you can talk about adjustments in respiratory or in pulmonary. Um, but just speak that out for everybody. Um, so that they're not anticipating you're going to talk about the plan there. If someone wanted to talk about the plan there in in our mind, it'd be a little bit out of order.
Uh but certainly you could. Uh but the things you're kind of thinking about are every day for every patient, are they ready for a spontaneous breathing trial?
This is absolutely critical. You should explicitly say yes or no. And if the answer is yes, they should get a spontaneously breathing trial.
Obviously, are they improving or worsening? Do you need to adjust any of their ventilator settings? Any signs of uh patient ventilator desynchrony uh is important to think about, too. Okay. So this might look like in your plan, you know, you already went through the whole ventilator. And you say something like patient has had improving oxygenation.
They're currently on an FI240% of PEPA 5. They're ready for a spontaneous breathing trial, which we will do this morning. Um or this could be the patient has had worsening hypoxmia uh in the setting of interval chest X-ray that showed a new pulmonary infiltrate. They are not ready for spontaneous breathing trial as their FO2 is up to 80%. uh we're going to increase their PEEP from 8 to 10 to uh assist in oxygenation and they are having a lot of ventilator desynchrony secondary to their typia we're going to you know do XYZ depending on what the DSynchrony is.
So if we were going to connect steps one which was mode, step two which was settings, step three which was pressures, step four which was ABG, step five which was are we hitting our goals, step six which was chest X-ray, and step seven which was clinical assessment which is usually in the plan. We would say something like patient X is on and we're just going to use we're not going to uh use the abbreviations. We're just going to use the order of things. So patient X is on ACVC 18 450 40% and 8 with an I to E of 1 to 3. Peak pressures are 30 to 40 plateau of 28 with a driving pressure of 14.
Most recent AG from 1 hour ago 7.34 48 and 68. Uh we are achieving our goals of SPO2 greater than 90%, most recent chest X-ray was from 3 hours ago.
Endotrachial tube was 3 centimeters above the corina. There was improving bilateral infiltrates as compared to the chest X-ray yesterday. And then forwarding to plan, uh patient has had improvement in oxygenation. Uh they ready for a spontaneous breathing trial which we'll do this morning. Uh they were comfortable without any ventilator desynchrony.
All right. Hopefully that wasn't too much but it is a lot. Uh but this is next level presenting on rounds. This is you know would be absolutely fantastic.
If we were to go down I think we wrote out an example too. We did um oh for the plan this is some if we were to kind of say the clinical assessment and plan you could say something like the patient's oxygenating well on F2 40% PE of 8.
Their plateau pressure remains less than 30. AG shows mild hypercapnea accepting in the setting of ARDS strategy with permissive hypercapneia. No Q changes on the chest X-ray. plan to continue current settings and reassess readiness for SPT tomorrow. Uh, another example of a plan. So, quick tips for success.
Always start with mode and settings. And really, this is all about repetition.
Stick to a single structure and just do that every day for every patient over and over and over again. All right? Use objective numbers, but then in the plan, interpret them clinically. Right? So, when you're presenting the numbers, just be objective. Don't use soft language like um you know their FO2 is around 40ish%.
Uh really use objective. Their FO2 is 40%. But then when you're interpreting them clinically you can interpret them.
Uh but when you're objective stay objective and when you are interpreting um you know you can come up with a plan and instill some subjectivity to that plan. Tailor your focus in the plan for whatever you're treating. Is it A or DS?
Is it COPD? Um and be ready to talk about the settings they're on. suggest weaning escalation and always talk about are they ready for their spontaneous breathing trial. Anyone on a ventilator, the goal is always to liberate them from that ventilator.
All right, hopefully that was helpful. I know it is a lot. We'll upload this as a study guide to our Patreon page. So, definitely check that out if you want access to the study guide. We'll also put some practice questions uh on there and it gives you easy access to us if you have questions or want to practice anything. So, certainly check that out um if you're interested. Uh we also have a ton of videos on mechanical ventilation. Uh YouTube members get early access. because we have a weekly newsletter. All that's linked in the description. Uh we appreciate you all.
Stay well. Keep learning. We'll see you next time.
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