What's up, future respiratory therapist? Hey, in this video, I'm going to use this ventilator to give you a graphical illustration of the difference between continuous mandatory ventilation versus assist control ventilation versus synchronized intermittent mandatory ventilation. Let's dive in. All right, so this is an illustration of volume control CMV. Now you may ask yourself, well what is CMV?
Well CMV is Controlled Mandatory Ventilation. So what that means is that the ventilator has a set respiratory rate, a set tidal volume, and a set flow. So we have a tidal volume of 500, a flow of 60 liters per minute, and a respiratory rate of 10 breaths per minute.
And when you look at your screen here, what you recognize is That there is a breath happening about every six seconds. So that's 0, 6, 12, 18. Every six seconds, let me freeze that again, you're getting the tidal volume of 500 at the flow of 60 liters per minute. This is going to be very, very important as we learn how to look at vent waveforms and decipher. is happening okay so that's what's happening the patient's not trying to breathe right now at all okay and so you see this is what it looks like now if i was to come in here and switch to volume control AC, this would be volume control assist control, then now we're in a mode of mechanical ventilation to where we're still giving a tidal volume of 500, still a flow of 60, a respiratory rate of 10. What we're going to see is that this is going to look very, very similar to CMV. A breath is going to happen every six seconds, 6, 12, 18, tidal volumes of 500 flow of 60. Everything looks very, very uniform.
Why? Because the ventilator is in control of everything. Now, if we compare that to volume control SIMV, then we just come in here and go look at VC SIMV.
And we accept that. Now you automatically see right here across the bottom that we have more settings. That's because we now have a pressure support and a slope.
But we still have tidal volume of 500 with a flow of 60 and a restore rate of 10. Again, a breath happening every 6 seconds. There's 6, there's 12, there's 18, there's 24. It's all happening in the same place. So you see where all these modes look the same because our tidal volume right here, 500, 500, 500, flow of 60, 60, 60. My point here is that there is no difference. between volume control CMV, volume control AC, and volume control SIMV when the patient is doing nothing. In other words, when there are no efforts on the patient's side to breathe.
Now, this is going to change when we start to implement a patient effort. So I'm going to go back to volume control CMV where we started. We're going to go back into this mode right here. We're now back in to volume control CMV and the patient's not doing anything right now. What we see here is that we have breaths happening every six seconds.
You're going to see that come up. Everything is very uniform because the vent is in control of volume and flow. See, I can change the pressure.
I can make the pressure go higher by changing the compliance of the test lung. Now, that's another conversation for another video. Right now, we're just looking to see what happens and what is the difference between CMV, AC, and SIMV. So what I'm going to do here is with my test lung, I'm going to start trying to make the test lung breathe. And what we see is that there are efforts happening, but look at the pressure waveform.
Nothing, right? There's nothing happening on the pressure waveform. Because the patient can't truly get a breath.
in between these controlled breaths. That's CMV. The patient cannot breathe spontaneously in between the set rates that are happening, the set controlled breaths.
So what's the difference in that in AC? Well, let's look at AC. Volume control AC. We come over here. There's breath one, six seconds.
There's another one happening where? 12 seconds. There's another one happening at 18. But I'm going to take a breath.
Oh look, there's another breath. There's another breath. There's another breath.
So see what's happening now is this patient is triggering breaths above the set rate. So we have a set rate of 10, but we currently have an actual rate. Around 20 right now 21 and I can make this go as fast as I want to I Can get this into the 30s all I have to do is just make the breaths happen faster now what this means is is that? While you see that there are more breaths happening. I want you to notice something Look at the volume waveform.
All these tidal volumes are the same. Look at the flow waveform. All these flow patterns are identical.
That's because while the patient can initiate all of these breaths, The ventilator is still in control to how much volume they get and how much flow they get. So how much they get and how fast they get it, not how quick they get it. The patient is in control of how quick they get it or how fast they get it.
often but the ventilator is in complete control of flow and volume. One other thing you'll notice here is when I take these breaths again and I initiate these breaths using a test lung. All I'm doing is just squeezing on a test lung here.
That's all I'm doing. Okay I'm just pulling on the test lung initiating a breath. When I stop, watch I'm going to stop one of these breaths at the 10 breath mark. There's 10 right there.
Look when the next one happens. No breaths, the next one's going to come right here at 16. Boom. Why? Because the ventilator knows I have to give a breath every six seconds. If the patient wants one, they can have one before that.
They just have to ask for it. And when they do, I'll wait another six seconds after that last breath to give another mandatory breath. Okay? So these are patient triggered breaths.
Ventilator controlled breaths. Now this is going to be very different when we go into SIMV. So let's go into volume control, synchronized, intermittent, mandatory ventilation.
So we're going to see a controlled breath here. I want you to see several controlled breaths. Like that. That's a control breath. There's going to be another one six seconds later because we're still on a rate of 10. Right there.
There's your next control breath. Now look what happens when I reset the screen here. Look what happens right here.
I'm going to start breathing spontaneously. Right here. Now what I want you to notice is, is that look at all the breaths.
That's a mandatory breath, that's a mandatory breath, but these breaths here, these are all spontaneous breaths. These are all pressure supported breaths. And look at our flow down here. It's a different color and that That signifies that we now have spontaneous breaths happening. These are all spontaneous.
These are all spontaneous. When you look at your volume waveform, look what's happening here. You have 500 mLs, 500 mls but look at our spontaneous breaths.
They are all smaller. Okay. Now here's the cool thing about this is They can be really small breaths So you look at your volume waveform here, you'll see some small little spontaneous breaths but I can also take a really big spontaneous breath and a small one and I'll get a mandatory breath Right there and then I can take another Another big breath.
See? So what we see here is that while we have mandatory breath, mandatory breath, mandatory breath, we also have small spontaneous breaths, small spontaneous breath. We also have very large spontaneous breaths right there.
All of these in the tan here are spontaneous. So what's the difference between CMV, AC, and SIMV? The answer is, is that in CMV...
I'll show you one more time here. In CMV, the patient cannot trigger any breaths above baseline on the pressure side of things. They can breathe within the circuit, but they can't generate any true volume.
Now, when we go to AC, We see that the patient is in control of rate, but the patient is not in control of individual breath size or flow. Everything is identical except for how fast breaths are delivered being the respiratory rate. And when we go into SIMV, We see that the patient is now allowed to truly breathe spontaneously in between the mandatory breaths, which are the blue breaths. That's a mandatory breath.
Now watch. Spontaneous, spontaneous, mandatory coming. mandatory. And we see where our volumes now vary and our flow varies based off of our patient's needs, but our mandatory breaths remain constant and unchanging. That's the difference.
between CMV AC and SIMV hey if you like this video and you like the way we showed you the difference between CMV AC si V using a ventilator do me a favor leave me a comment below tell me what you liked about it tell me what else you want to see while I have this villain in my hands also do me a favor hit the subscribe button turn on all Bell notifications we really love for you to join this great respiratory coach YouTube community love to have you be a part of that and as always you can always reach me on all the socials, respiratorycoach on Instagram, respiratorycoach at TikTok, coachRT on Twitter, respiratorycoach at gmail.com. If you have any questions, feel free to reach out to me for that. And then you can always text me, 817-968-7035.
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