Hi, welcome our video series on life-threatening lung disorders.
In this particular one, we're gonna take an in-depth look at acute respiratory distress syndrome.
Now, you probably heard that referred to as ARDS.
You've seen in the news, you've seen it in your textbooks,
now I wanna help you gain a deeper understanding of that.
So let's start with something fun. Take a look at the chest x-ray.
Now, on the left those are what normal lungs would look like,
hopefully, that's what mine would look like on a chest x-ray
and what yours would look like on a chest x-ray. Now the one next to it.
See, this is what happens typically in ARDS.
Look at the difference, the one on the left has all the dark space,
that's where the good stuff happens, that's where the CO2 and the O2 are exchanged in your lungs.
On the right, you notice you've got all that whiteout area.
We call the opacities, can't see through it.
Air is not able to be exchanged there, that's not functional tissue in your lungs.
So in this video series, I'm gonna help you understand on a cellular level
what is causing that whiteout on your chest x-ray.
What makes a patient go into ARDS? It's gonna be a lot of fun so hang with me.
Keep in mind ARDS is a clinical syndrome, okay, it's not a disease, it's a clinical syndrome.
Now, it's got some special characteristics.
The first one, as you can imagine from that x-ray, severe hypoxemia.
Now, that means low - hypo, ox - oxygen, -emia - in the blood; so severe hypoxemia. Why?
Look how much less lung tissue the patient has to work with,
look at those opacities, that whiteout on the chest x-ray.
That's why we can't get oxygen from the lungs into the blood stream
because of the damage and the hits that tissue has taken.
Second one, we talk about those bilateral infiltrates on their chest radiograph,
that's a fancy way of saying chest x-ray and you can see those right there.
Now, you won't be able to interpret chest x-rays by the time you're done with this video series,
but you and I can easily see the difference between normal lungs
and what we see when a patient is in ARDS.
The third one is reduced pulmonary compliance.
Okay, your lungs need to expand and then recoil; expand and then recoil.
So that's compliance, the lungs ability to do that, they need to be healthy.
In ARDS the lungs become stiff, I'll help you understand why,
but the lungs become very stiff and so they're not as compliant.
They're not able to expand and recoil.
Okay, so those are the three main characteristics, severe hypoxemia,
you've got the infiltrates on chest x-ray, and you've got reduced pulmonary compliance.
We get more specific than that but that's the first overall framework I want you to lay down.
So, tell me, what do you think of the three most important things for normal lung compliance?
Okay, if you've hung out with us in other videos you already know the answer,
if you haven't we're gonna bring you up to speed.
So, you need an intact alveolar wall, you need an intact capillary wall, and you need surfactant.
Take a look at our picture there that we have for you.
Okay, so I wanted this one right next to the lungs to kinda help set the stage
as we're walking through this ARDS video.
That is one of the alveoli, so it's an alveolus.
Now, follow its kind of globe-shaped, we've got that.
The outside wall is one cell thick, very fragile.
Now, the capillary membrane, look, they touch right next to each other,
there's a basement membrane in between,
but the alveoli and the capillary are in very close connection
because that's where the CO2 and the O2 exchange.
Remember it's those type 1, beautiful and elegant cells where the CO2 and O2 actually exchange.
Now, in the wall, see those little shorts stocky guys, right?
Those are the type 2 cells, those are the ones that secrete surfactant and surfactant
is what helps keep those alveoli open and keep them from collapsing,
because that blue line in the alveolus, yeah, those alveoli are lined with water.
Water has surface tension that makes it want to shrink to its smallest space
but surfactant pushes its way in there, breaks up that surface tension
and helps prevent or minimize the risk of that alveoli for collapsing.
So if I want lungs that can -- if I can do that, if they can expand and they can recoil,
they need to have an intact alveolar wall.
They need to have an intact capillary wall, and they need to have sufficient surfactant.