That you may have heard that term before, you'll often hear it called ARDS.
ARDS is a clinical syndrome so it's not like COPD as a disease, right?
Pneumonia is a disease.
We've got ARDS as a syndrome, so it's a clinical syndrome.
So it has to have this characteristics.
Now, before we look at it look at those two chest X-rays.
Note the differences? Yeah, let me explain what that really is.
Now, the first characteristic is the patient has to have severe hypoxemia.
I wanna break that word down.
So, underline hypo, right, that is meaning low, not enough.
Then we're gonna borrow that "o" and connect it with the "x" that talks about oxygen
and then the last part -emia means in the blood,
so severe hypoxemia means severely low oxygen in the blood.
That's the first characteristic of ARDS.
Now, they have to have bilateral infiltrates, now we get to do some fun stuff.
You don't have to know how to interpret chest x-rays at this point,
but you can easily look at the normal lungs and the lungs that are typical of ARDS
and you can see those white spaces, those are the bilateral infiltrates.
Infiltrates do not exchange oxygen and CO2 well that's why this patient is struggling,
that's why you've got a PaO2/FiO2 of 100
because that's what this patient's lungs likely looked like.
Now, in addition to that, we've got these areas of infiltrate, you've got reduced pulmonary compliance.
Hey, that sounds real fancy but all that means is lungs in order to function, when I take a breath,
remember that my diaphragm flattens out, my rib cage comes up and out
and I have more room for my lungs to expand, right?
Then after I take a breath and I let it out, everything gets smaller again.
So that's what compliance is, the lungs ability to get elastic, right, to stretch
when I breathe in to go back to normal size, so this is what compliance is.
People that are in ARDS is more like this, so they can't get air in very well,
you've got these alveoli that are all jacked up.
You've got stiffness, you've got infiltrates that's why you end up with a PaO2/FiO2 that's so low.
Now there's a lot of controversy over what is ARDS.
What is an ARDS? Is this ARDS?
No, that's ARDS. So, we got a bunch of experts together.
Well, I didn't personally get them together but a group of experts got together
and this is the Berlin definition of ARDS, that's where they got together.
So, within the first week of known clinical insult
or a new or worsening respiratory symptoms, here's what has to happen.
Bilateral opacities on the chest imaging not fully explained by effusions,
or by lung collapse or nodules.
Now, these are not my works, okay?
There are the official medical definitions, but I wanna walk you through what they are.
You just saw that chest x-ray so those opacities on both sides, that's what they're talking about.
When you look at the chest x-ray you're gonna see those white areas.
Now we can't explain them with a pleural ef6fusion, with a lung collapse
or any other nodule so we don't have any of those reasons that would cause those opacities.
And they have respiratory failure that's not explained by cardiac failure or fluid volume overload.
So, see, it's kinda like we're gonna check and make sure this isn't this, and make sure, it isn't this,
and make sure it isn't this before we call it ARDS.
So, the patient can't be a CHF or somebody who is extremely fluid volume overload
because that might be another explanation for those opacities
and what they see in the chest x-ray.
The third criteria in that first category is an objective assessment
such as an echocardiography to exclude hydrostatic edema if no risk factor present.
Okay, that's a mouthful, but you know that is an echocardiogram.
They're looking at the function of the heart
because we want to make sure that the heart isn't the cause of the problem.
So if you're gonna diagnose it as ARDS, it cannot be the heart's fault.
So once we took off what we think it isn't, now we're talking about impaired oxygenation.
So two big categories, it has to happen within the first week of the known clinical insult.
So this could be a pneumonia, some type of injury, a major trauma,
that's what the clinical insult is.
There's the first category. The second category is impaired oxygenation.
Now, look at how they described it. See this is what I really want to focus on.
They've grouped, this Berlin definition of ARDS, has grouped ARDS into three categories.
I love these names cuz I can spell them, right? Mild, moderate, severe.
Alright, everybody's with me. We can all handle mild, moderate, or severe.
I think you can tell you would rather have a mild case of ARDS than a severe case of ARDS.
But here's how they define it. Look, It's the PaO2/FiO2 ratio. Cool.
We already know how to do that.
So you're expecting a PaO2/FiO2 ratio between 200-300 with ventilators settings PEEP
or CPAP greater than five centimeters of water.
Hey, if you don't understand ventilators settings yet, that's okay.
This is just gonna help with if they have to be on the ventilator
and we've got PEEP which is positive-end expiratory pressure,
it's just a little extra pressure at the end of expiring so you keep those alveoli open.
So they're very specific, this is what the PF ratio is, I just shortened that, right?
The PF ratio, because most people don't go around saying, "What is the PaO2/FiO2?"
They say PF. So for mild, the PF ration is between 200-300,
they're on the vent and they've got PEEP or CPAP greater than five centimeters of water.
Moderate, yeah, you're gonna expect that PF ratio to be lower, good,
and there it is, between 100-200 with those same PEEP settings.
Now, severe, look at that. The PaO2/FiO2 or the PF is less than a hundred with PEEP.
Now our patient that we did was right on the line at a hundred,
so you're pretty close to severe, right?
That's someone who is really in tough shape.
Remember, this is a continuum so just because if my PF ratio is a 100,
that really doesn't mean, oh, at least I'm not severe.
No, I'm still in pretty bad shape.
This just gives us a common language to communicate with each other.