- Hey everyone,
I have Adam with me here today to learn about APRV,
but before we start, I just wanna say quickly
that I wanna dedicate this video to my father-in-law,
my father-in-law's a physician in Staten Island, New York,
who died last week, because he was caring for his patients
who had COVID.
So this goes out to him, so we love you Dr. Alex,
or I like preferred to call him Lolo,
so, I love you Lolo.
Okay.
So, let's move on, okay Adam?
So, we're gonna talk about
Airway Pressure Release Ventilation today.
This is very similar to one that we did already last week.
So folks at home,
if you haven't watched the ventilator basics
for non-intensive as part two,
please go back and do that before you watch this video,
coz it'll feed into what we're gonna learn.
So Adam, if you were gonna order AC-PC
from your respiratory therapist, what would you ask for?
- [Adam] So there'd be five things that I'd ask for,
so the mode for AC-PC, respiratory rate, Phigh, a PEEP,
an FiO2.
- Okay, that's perfect.
Okay.
So, if you had your patients on these settings,
say we chose a respiratory rate of 12, a Phigh of 15,
a PEEP of five and an FiO2 of 40%
and you wanted to,
your patient wasn't oxygenating well enough
and you wanted them to oxygenate better,
how would you do that?
- [Adam] So, I would look at the PEEP and the FiO2.
- Okay, perfect.
Which is generally how we take it
and that's why we write it this way, right?
These are our ventilation parameters,
these are our oxygenation parameters.
Okay.
So, we generally think of using these two parameters
as the way to increase oxygen,
but I want you to shift your thinking for today.
We're gonna incorporate another variable,
which is your I:E ratio.
So, instead of thinking of this number
as your PEEP increasing option,
I want you to think about your mean airway pressure
increasing your oxygenation.
Okay?
Alright.
So, if I had you on these settings,
I would have a PEEP of five,
I would go up instantaneously to 15,
I would stay there for some amount of time,
I'd come back down to my baseline
and then I would do the same thing,
and whether the patient tried to take a breath
or the machine tried to take a breath, either way,
it's gonna be the same kind of looking breath
that is gonna be cycled by time, by your I:E ratio.
Okay?
So, let's say for a respiratory rate of 12,
that's five breaths, five seconds per breath, right?
So, let's say this is one second and this is four seconds,
okay?
So that's our I:E ratio would be one to four.
Cool, with me so far?
Alright.
So, that's all fine and good until I get to a place where
my patient is now at a Phigh of 30.
We ever wanna go higher than a Phigh of 30?
- [Adam] We do not.
- We never want to, right?
That's like the equivalent of our plateau pressure
on this setting, we don't wanna damage the lungs,
we never wanna go above 30.
Okay.
And then let's say that our FiO2 was 100,
not 10, 100,
right?
Then I'm starting to struggle more about
how to help my oxygenation.
Okay.
So, if we get into that situation
and we have a patient with severe ARDS
and we want them to be on a different mode
that would help them oxygenate better,
we think of shifting from this mode, AC-PC,
to Airway Pressure Release Ventilation, APRV.
Okay?
And this is what that would look like.
So, now we sort of go through a progression, this is AC-PC.
Once I extend this T-High longer than my T-Low,
now I'm in a phase we call BiLevel
meaning two different levels of pressure.
Okay, cool?
And then as we progress even further along this continuum,
so that would look like that,
we get to something that actually resembles that.
So, we're at that Phigh almost all the time.
Does that make sense so far?
- [Adam] That does.
- Okay.
Awesome.
So, I just wanna talk about a little bit
what we're talking about.
So, if I was here
and I was at that first settings
my mean airway pressure would be for one second,
I would be at 30 and for four seconds I would be at five.
So, if I was sort of doing an area under the curve
of this area, it would be 50 seconds
and then I would divide that by the total five seconds,
so my mean airway pressure here would be about 10.
Okay?
Trust me on the math for now, okay?
But if I change this, and now I'm up here for four seconds
and down here for one second,
now I'm 125 divided by five,
so, now my mean airway pressure
has gone all the way up to 25.
That mean airway pressure
allows me to keep all those alveoli open
and doing the gas exchange.
Okay?
So, that's why that mean airway pressure
helps oxygenation so much.
Cool?
- [Adam] Cool.
- Alright.
So, this is technically BiLevel,
but if we go to the absolute extreme of this,
then we shift into APRV.
Okay?
So, I'm gonna take it now
and I'm gonna do this,
for 4.5 seconds
and I'm gonna do this, for 0.5 seconds.
Alright?
And instead of having a PEEP of five
we're gonna have a PEEP actually a zero.
Okay?
When we think about the settings for APRV,
we think about a Phigh,
a Plow,
a T-High
and a T-Low
and an FiO2.
Okay?
Those are my settings.
Drager ventilators make this super easy.
If we're on a different ventilator,
say maybe a Puritan Bennett ventilator,
we have to do a little bit of math,
I'll talk about that in a second, how to do that.
You can't do this mode on like transport ventilators
or things like that.
Okay?
Alright.
So, right now the way it's set up, my Phigh is 30,
my Plow is zero,
my T-High is 4.5 seconds,
my T-Low is five seconds
and let's say, my FiO2 is 100%.
What's my I:E ratio, now?
4.5 to five.
So it's nine to one. - [Adam] Nine, one.
- Yeah.
So I've dramatically changed my I:E ratio.
Okay?
And you're probably thinking,
"I've always been told never to go to a PEEP of zero".
Have you been told to never go to a PEEP of zero?
Why?
Why don't you do that?
- [Adam] Because you don't want to derecruit the alveoli.
- Right, you don't want them to collapse first of all,
coz then they might just stay collapsed,
but also the more they open and close,
the more of them are gonna break.
We don't want them to break,
so, we don't wanna damage our lungs,
we don't wanna derecruit lungs, right?
So, we don't actually go to five.
So, we have to make sure this time is short enough
for us to never actually get to that zero,
this is a key part of APRV.
We can't let our patients sit down at a PEEP of zero.
That's not gonna work, right?
It's gonna derecruit,
it's against everything we're trying to accomplish
with this mode.
Okay? - [Adam] Okay.
- So, these are great initial settings for someone on APRV.
There's another beauty to having someone on APRV and that's,
they can breathe over this whenever they want.
So, we give them tube compensation
or a little extra pressure support, something like that
so that they can take their own breaths,
feel a little bit more comfortable,
move their own lungs as they want to.
Does that make sense?
- [Adam] Mhhm.
- Okay.
Alright.
So, you have a good idea of this.
In reality, if I'm gonna put someone on this,
I try to keep that Phigh at 25,
so that I can give them that extra five
that they can take their own breaths with
without breaking that threshold of 30.
- [Adam] Okay.
- Okay.
If they're not super sick
and they don't need this high of a setting,
you can start by just setting the Phigh
at what their mean airway pressure was before
and sort of work on it from there.
- [Adam] Okay.
- Okay.
But generally when we're starting someone on this,
we're doing it as sort of an oxygenation salvage therapy,
so they usually need high settings when you get started?
Cool?
Alright.
So, they're breathing over it,
they're at this high pressure almost all the time,
not letting this get to zero.
Okay?
We'll say that this is 25 up here.
So, now my mean airway pressure is like 24.5
or something really high, right?
I've really optimized that mean airway pressure
and I'm already optimizing my oxygenation.
- [Adam] Okay.
- Okay?
So, now I have them on this mode,
what do I do if they're getting better?
- [Adam] Do you start decreasing the Phigh?
- Exactly, exactly.
So, we do what we call drop and stretch.
Okay?
So, we go from here,
to maybe we would say,
"Let's go to 20".
So, we'll go to 20,
we'll increase our T-High to 5.5 seconds,
our T-Low generally can stay at about that 0.5 seconds.
Okay?
And then we do that again for 15,
but eventually we sort of drop and stretch to Foreverland.
What do we call it when we're at 10 for Foreverland?
- [Adam] Like continuous positive airway--
- Yeah, that's CPAP, right?
So, we titrate them right down to CPAP
and when they're on CPAP,
then we can start doing spontaneous breathing trials,
get them off the ventilator.
Okay?
So, we don't ever have to take them off of this,
we just drop and stretch it down.
- [Adam] Okay.
- Okay?
One more key point I want you to know about,
so, in general when I've been doing all these videos,
I always draw this curve,
which is,
my pressure versus time curve.
Okay?
When you're doing APRV,
it becomes really important to also watch your flow curves.
Okay?
So, now I'm gonna add time and flow.
Okay?
And generally what's gonna happen is,
they're gonna take some breaths, sort of be going like this,
and then they're gonna have this negative breath
and then they're gonna start coming back
and we don't want this to get to zero,
so, we don't want flow to hit zero before they come back up.
Does that make sense?
So, just like we don't want this to hit zero,
we also don't want this to hit zero.
- [Adam] Okay.
- Okay?
So, when we're trying to figure out
what this optimal T-Low is,
0.5 is a pretty safe one to get started with,
but we wanna really go in
and watch what percent of our end expiratory flow we are at
before the next breath starts,
we really wanna watch what our pressure ends up being here.
Okay?
So that we know what our driving pressure is,
we know we're not hitting zero,
so, we really have to pay attention to both curves.
- [Adam] Okay.
- Okay?
- [Adam] So every time you like drop and stretch,
do you re-evaluate to look at the PEEP level?
- Yeah, that's a great question.
So, often at 0.5 you're gonna be pretty safe
at pressures of like 20, 16 those sort,
you'll be okay with 0.5 but still, go in and watch again
and make sure that this isn't happening.
- [Adam] Okay.
- Okay?
Drager ventilators have a safety glitch you can put on
that's called AutoRelease that you can set,
and so this 0.5 would be the maximum time,
but if I can't use that much,
that release time will fix that for me.
- [Adam] Okay.
- Okay?
So, you can do that on that,
but you can't do that on say a Puritan Bennett ventilator,
you have to stand there, watch your curves,
decide what's right for your patients,
and maybe this will have to go down to 0.4,
something like that.
- [Adam] Okay.
- But that's really quick, right?
So, you'll see,
if the patients will start dropping a little bit lower,
so just keep your eye on it.
Great question.
What other questions can I answer for you?
- [Adam] So, about the Phigh of 10
is when you start considering CPAP?
- Yeah, you can even go higher.
So, I would even say at 15, you can just go straight to CPAP
and leave them at a CPAP of 15,
let them do their own breathing above and below that.
- [Adam] Okay.
- Okay?
And if you have them on tube compensation
or a little bit of extra pressure support, great.
- [Adam] Okay.
- Okay?
So, one quick thing I wanna mention.
So, I said if you have someone on a Drager ventilator,
you can just set it up like this,
but on a Puritan Bennett they don't have an APRV mode on it.
Okay?
So, if we were on a Drager ventilator,
to get those same settings,
we would put them on
AC-PC,
at a rate of 12,
so five seconds per breath.
Right?
We would have them at a Phigh of 25,
a PEEP of zero
and an FiO2 of 100, say whatever you needed,
and then you have to go in
and there's actually an I:E that you can change
and you have to keep dialing that knob
until you get this to that
4.5 to 0.5
that you're looking for.
- [Adam] Okay.
- As far as that I:E ratio.
Okay?
So, you have to do a little bit more math
to get to this point, but it's the same thing.
Okay?
- [Adam] Okay.
- Does that make sense?
- [Adam] It does.
- Any other questions for me about that?
Okay.
Any questions?
- [Male Voice] So, a lot of these patients
are coming into ARDS
and they get put on paralytics on earlier modes.
- Yeah.
- [Male Voice] Can you use paralytics in this question?
- Yeah, that's a great question?
So, always in this mode,
we wanna pay a lot of attention to our ventilatory status,
right?
Coz this can make us hyperventilate.
But it is still possible
to use this mode in paralyzed patients,
you just have to keep even a closer eye
on your ventilatory status.
Okay?
So, if generally if you have people doing this,
12 releases a minute,
they're still going to ventilate pretty decently
and we're gonna tolerate some permissive hypercapnia
for the benefit of oxygenating them.
Right?
High PCO2 doesn't kill our brain cells,
but low O2 kills our brain cells,
so that's what we care about.
Okay?
So you can do it, it's not ideal
coz then they're not gonna be
taking these extra breaths over it
with that extra ventilation, but it is doable.
Okay?
Any other questions?
Alright, thanks so much for your time today.
Have a great day, guys.