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Learn what the main classifications of lung diseases are: obstructive, restrictive, ventilation, and perfusion. Discover the classification of common diseases like asthma, emphysema, and pneumonia. Created by Amy Fan.
Video transcript
Voiceover: So the job of our lungs on a pretty general level is to take blood, that's without oxygen that our bodies have used up. So I'm going to use blue here to represent that. To take that blood and to put oxygen in it, and it comes out as oxygenated, which is red blood. I mean blood without oxygen gets a little darker, that's why conventionally we think of it as blue versus red. And from there the heart pumps this blood to the rest of the body. So in a nutshell, that's what the lungs do. And to do that, they grab oxygen from the atmosphere and take the carbon dioxide from the blood and blow it out. Co2, carbon dioxide. And this exchange really is a full picture of what you do with every breath. Now in terms of how the lungs do this, let's talk about the structure first for a bit. I think it looks kind of like an upside down tree, just because all these branches keep getting smaller and smaller as we reached the terminal branches. I mean there's 20 or 30 levels here, I can't draw them all, but you get the idea, they keep branching off. And at the end, we've reached this units called alveoli. Let me write that word for you, alveoli. Which is plural for alveolus. And what that is essentially an air sac. Let's blow that up down here. So the alveolus looks kind of like a bulb, is an air sac, it has very thin walls, and laying along the walls, almost, almost in contact but not quite, is the blood supply. This is how things get from our blood to the lungs and back and forth. So I'm going to draw a blue here to begin with because there's no oxygen to begin with. As it travels and that the air goes back and forth between the blood supply and the alveolus, it becomes red as it leaves, because there's oxygen. You can think of it as inhale, oxygen goes in, from here it goes to the blood supply. It makes you exhale, the carbon dioxide is going the opposite way. When we exhale it can just leave the lungs. And now the reason this exchange takes place is just a simple loss of air pressure in physics. So if there's more oxygen in here, relatively more compare to the blood supply, then the oxygen wants to escape to the blood supply. And if there's relatively more carbon dioxide in the blood, then it also wants to escape to where there's less of it, which is into the air sac. So conveniently this allows us to take what we want and get rid of or it don't want anymore. Okay, so there's your bird eye view of how the lungs work in a nutshell. And there's a lot of problems that can arise in this whole system. But I think a better way to understand it is to break it down by the different players, the different areas that can go wrong. So again we think of lung problems as categories. Now, the first one, the first problem I can think of is oxygen not coming in. And so on the flip side of that, number two would be carbon dioxide not escaping. All right to keep going, let's go further into the lungs. Here at the alveolus, I would say number three is something going on with this exchange process where between the air sac and the blood supply, something is not working there, so that's number three, that's the exchange. And lastly, if something is wrong with the blood supply, blood cannot get to the lungs and come out, that would be number four. So I think these are the four big categories of lung diseases. And let's go through them one by one. Now problems number one and two here, we actually think of them as a pair of diseases, there's restrictive and obstructive. Let's start with restrictive. And this just describes the fact that the lungs which are suppose to expand when you take air in to make room for the air, for some reason it's not expanding properly. So this is an intake in respiration problem. And since oxygen is the main point of taking air in, in restrictive diseases we lack oxygen. So what happens is, the lungs for a variety of reasons becomes stiff and hard to blow up like a balloon that's been dipped in paper mache and it can't blow up properly. So if you look at, if this is suppose to be the size of the lung when it's blown up, this smaller lung her in restrictive disease gives us a lot of wasted space, other space that could have had oxygen but is now not usable. That just makes the whole system less efficient, right? So there's something wrong with the actual structure of the lungs that's making it hard to expand. So let's think of some examples. So there's fibrosis. Fibrosis just means, laying down too much scar tissue. So if the lungs are chronically injured or sometimes there's a genetic factor to it, the tissue gets stiff. Just like the scar you would have on your hand, except you have all over your lungs. So it's not, no longer expandable. There's also things that can affect the chest wall. Say if there's a muscular diseases that make it hard for the chest to expand, that also limits how big the lungs can get. Or sometimes there could be things that are deposited in the actual tissue of the lungs, I can think of amyloidosis, which is these protein particles that get studded into the lungs, making it harder to expand. So those are our examples of restrictive disease, oxygen cannot get in. Now it's evil twin, or I guess they are both evil, but it's counterpart would be obstructive disease. Obstructive. So if we said before that, the restrictive is about not getting air in, then the opposite will not be getting air out. In restrictive diseases we're having trouble with expiration. So instead of letting the lungs collapse back to it's normal size at the end of an exhale. It stays expanded like this. Let me just draw some of the branches here just to show you. There's different reasons that obstructive diseases can occur. Sometimes, let's say there's a mucous plug. An air can't get out or sometimes these airways collapse because the walls have loss it's elastic quality structure. So the air is essentially stuck in there. Let's think of all these extra air. Can you imagine how difficult it would be if you cannot exhale, that's very uncomfortable. So obstructive disease describes large, over-inflated lungs. And some examples would be something you probably heard of as COPD, which is actually a group of two different diseases. One is emphysema, which have to do with the lungs losing their elastic quality, and the other one is chronic bronchitis, which is just a lot of irritation day in and day out, that makes a lot of mucous. Both of these result in this large inflated lungs. Something more common that a lot of people have is asthma, which is when the air ways spasm and they close up, blocking the air from getting out. So restrictive and obstructive diseases going have to do with a global picture of the lung. Not to get into too much of the detail, just think of restrictive as having trouble getting air in, oxygen in, and obstructive, having trouble getting carbon dioxide out with the exhale. So now let's zoom back in to the alveoli. What's going on down here that could give us lung disease. So number three I said there's something wrong with exchange. So let me just redraw this here. We have our air sac, so air has finally made it here to where it can make contact with the blood supply. And one thing that will really mess up this process is let's say if this air sac is filled with fluid. Like that. Let's fill that in to make it, yeah, like that. Okay, so what would happen to your oxygen, so it's coming in here, it wants to get to the blood and uh-oh, it's stuck. As you know it's much harder for air to diffuse through liquid than it is when it's empty space. And then on the other hand, carbon dioxide is here trying to get out and uh-oh it's stuck in the fluid too. So as you this makes the whole exchange much less efficient. So you have less oxygen going in and less carbon dioxide going out. So that when, I would say that this blue, let's extend this a little further, instead of turning red where it's suppose to, since it's so inefficient, it eventually becomes as kind of weak red when it leaves. So you have less oxygen in your blood and more to carbon dioxide than you would in a healthy lung. So what could cause this to happen with the fluid. One thing that's very common is an infection such as pneumonia. See when our lungs are not doing well, there's a lot of secretions, mucous, which is fluid trying to flush out, wash out what's there. So pneumonia, if it's bacteria or virus this fluid happens. There's also edema. Edema kind of is just a general word for a fluid being where it's not suppose to, being pushed out. So, if for some reason if there's too much blood in the blood supply. Let's say if your heart is not working well, and all this blood is backed up, then it will flow into the air sac where it does not belong and give us this picture of wet inefficient lung. And usually the lungs works best when they are dry, because we're talking about air exchange here. I forgot to write a name for this category, let's call this ventilation. We're talking about the exchange here, but ventilation technically means getting carbon dioxide out of here. But I want to use this word to just describe the process of exchanging one gas for the other. Which is not working well here. And talking about wet versus dry lungs here, it kind of goes nicely into our fourth point. So our fourth problem, let's call it a problem with perfusion. So it's funny, it's kind of like the lungs are too dry. So perfusion is the ability to get blood where it's suppose to go. Again let's draw our alveolus, singular, it's alveolus. So we have our blood supply coming in as usual and uh-oh, sometimes there can be a clot. So our body can make clot and they can break off and float in the blood stream when they get to a place that's small enough to get stuck, they get stuck here. And stops the blood from flowing pass this point. So for the rest of the path, there's no blood. And the branches of blood supply, the branches of past this point are also gone. So as you can see in this scenario, no matter how much oxygen we have in here, we only have, we don't have any blood supply to put it into. So not having enough perfusion is a huge problem, and we call it a pulmonary embolus. So pulmonary means it's in the lungs. Embolus describes a clot that formed somewhere else and it's travelled. And if it gets lodged in the lungs and it's a pulmonary embolus, now the severity of this really has to do with where in the blood supply get stuck. So let me just go back here, up here and draw some blood vessels along these trees. So if this embolus is all the way up here in a major branch and it shuts off this whole part of the lung. They have a huge problem, people can die from this. Now if it's a very small branch, like down here, then it's still uncomfortable and you'll lose a portion of the lungs but it's not relatively not as a big of a problem. But of course it will still compromise how well your lungs are working, how much oxygen is getting in, so on and so forth. So here you have four very general categories of lung disease that I think provides a nice structure for, okay, what are the different players involved, and what can go wrong to give us lung disease?