It’s such amouthful to say chronic obstructive pulmonarydisease, so since there’s an acronym for everythingwe just call this COPD. Chronic means it develops and happens over a long, long period of time. Pulmonary disease meansit happens in the lungs. But obstructive isreally the key word here, and we’ll come back tothis in just a second to describe exactlywhat’s obstructed here. But first let’s draw some airways. You have your trachea, that’swhere air enters the airway. To me the whole thing lookskind of like an upside down tree where you have these branchesthat keep branching off. There’s 20 or 30 branches,I can’t draw them all, but you can imagine itjust keeps getting smaller and smaller, just likebranches on a real tree. As they get to the end of a unit here, let me draw it where there’s more space, we encounter something thatkind of looks like this, it’s kind of like acluster of little bubbles. We call this the alveoli cluster. Alveoli is plural for alveolus. It’s a Latin thing to make theplural into an -i at the end. All of these are alveoli. In fact, aside from thecluster at the end they happen around on thestem near the end of the cluster as well, kindof on the tree branch. To get into the nitty-gritty, this is where emphysema happens. Let’s just blow up that end unit there and get a better look. You have your terminal branch here. The way I’m drawing this kind of looks like little clusters of tents. You’ll see in just a second why I’m drawing it in particular like this. I’m trying to get acrossthe idea that there are walls separating eachalveolus from each other. The walls have alveoli andat end you have your cluster. This is what the wholething looks like at the top of the breath whenit’s filled with air. I’m really tempted tocompare this to a balloon that’s blowing up, but we have to keep in mind that the comparison between lungs and balloons only exist during expiration. In a second we’ll see whathappens during expiration but first, just to beclear, let me explain why it’s only expirationthat’s like a balloon. When you have a balloon, this is your regular balloonand you have air going in, usually there’s positivepressure out here putting air in. Either you’re blowinginto it or it’s hooked up to a machine or somethingand that’s how air gets in. But in the lungs during inspiration, nothing is blowing into yourmouth forcing the air in. The air comes in by anegative pressure inside. The way that happens isbecause our chest wall, it’s kind of like a boxoutside the balloon. It expands with muscles,and as they expand it takes the walls of the balloon with it, and that negative pressureis how air goes in. But we’re really not concernedwith inspiration right now because obstructivediseases are expiratory. Regardless of how the air gotin there we can start thinking of it exactly like a balloonat the top of a breath now. When you let a balloon go theair just rushes right out, it’s the same thing in your lungs. As soon as you relax the wallsof this airway pushes the air out, because thewonderful protein that we call elastin that makes up thestructure of these walls. Whoever named this really thoughtit through because elastin describes the fact that it’selastic, like a rubber band. As soon as the lungs relaxthese walls snap back to their regular size, kind of like this. Not very much air insideat all, because the recoil strength of these wallspushes the air out. Now in COPD what happens isthis elastin gets destroyed. I just said that elastingives the elastic quality of the walls, so whenthat’s gone, the elastic quality of these partitioningsthat hold their structure, that give their recoil strength,that’s all gone as well. Instead of looking like aperky balloon animal with all these shapes, I thinkof a lung that has COPD, or this same structure, sameunit of the lung that has COPD, kind of looks like thisamorphous blob because the walls have lost their structure,they’ve lost their recoil strength, so they don’thold their original shape. It’s kind of floppy, kind of like a plastic bag instead of a balloon. When you have a plastic bag and you let it go air does not rush out, there’s no recoil strengthmaking the walls snap back. It kind of just stayshere and nothing happens. That’s the first step, andto make matters worse in emphysema, what happensis here in the stem of the airway this area actuallycollapses and forms a physical obstructionto the air coming out. The reason that happens,I kind of like to think of it as what happenswhen you have an open door in your house andit’s a windy day or breezy. As the wind goes through this open airway sometimes the door just shuts with it, and you hear this loud, itsuddenly pulls the door shut. It’s kind of the samething, that as air is trying to get out here itpulls the walls with it. Usually there’s elastin andstructure to the walls so this remains open, but here withoutall that the walls just want to go with the air,such that it collapses here. Now you have all these airbehind it that cannot get out. Not only are the walls not pushing it out but now you have a closed door. These things combined together is what gives you obstructed disease. COPD technically refersto two different diseases. There’s emphysema, which iswhat we’re talking about today, with elastin destruction, andthere’s chronic bronchitis. Anything -itis just means inflammation or irritation to an area,the airway is irritated. Depending on how this persongot the disease a lot of times these two variationsof COPD can exist together in one person, but todaywe’re just talking about emphysema in terms of elastin destruction. Okay, so where were we. We talked about how there’s all this extra air in here that cannot escape your lungs. You might think, “Sowhat? I work all day to “get air into my lungs,that’s the whole point,” and you would be half correct. If we imagine that there’sa blood supply here, I mean the blood supplyin the airways go together because they need toform an exchange system. Oxygen is usually in the lungsthat we pulled from the air, so oxygen goes into ourblood stream making it red. Then the other half of the dealis that we have carbon dioxide that the blood brings tothe lung to get rid of. These are made by our tissues after they’ve used up the oxygen. It’s kind of like a waste product. This needs to go back into the lungs and out through our mouth, and this exchange is really the complete job of our lungs. With obstructed diseaseyou can do half of it. You can put oxygen in but ifyou can’t get carbon dioxide out it’s just as big ofa problem as not getting oxygen because half of ourexchange is not working. There’s the root of allthe problems in emphysema. We have about 2.5 million ofthese alveoli in our lungs. Let’s imagine that allof them have lost their elastin and they look like floppy bags. What would emphysema actually look like? If you have your regular lungsthat usually look like this, which I hope that your lungsdon’t look like this but I’m sorry, I can’t drawany better right now. That’s what they usually look like, and if they’re filled allthe way up and air can’t get out it reminds me of big pillow cases. Day in and day out they’re over-inflated and they can’t go back down. As this person has emphysemafor a long, long time – remember it’s chronic -the ribcage and the tissue out of the chest actuallychanges shape because the lungs are pushing on it all the time. I don’t know if you cantell what I’m drawing at all here but what I’mtrying to draw is a barrel. People who have COPD areoften described as having a barrel chest, whichmeans they’re almost as far from front to back as theyare from left to right. With this shape changingthis person is very uncomfortable to have tocarry around such a huge, round chest and have airnot being able to get out. I need to give him some hair. I feel like that’s the only way my stick people can look like real people. He’s unhappy because his chest is like a barrel sitting there,he can’t deflate it. There’s a special way that people with emphysema often breaththat have earned them the infamous nicknameof being a pink puffer. There are two things that thisname is trying to describe. Pink is because they don’t lack oxygen, so pink instead of blue. Remember I said that theoxygen getting into the lungs is not a problem, ourproblem is in exhaling. They’re pink because they don’t really lack oxygen in their blood. Puffers describes the factthat they have pursed lips. Pursed lips, kind of like ifyou imagine putting your mouth around a straw, and they breathethrough this smaller opening. The reason for this goes backto this mechanical obstruction we talked about earlierwith the door slamming shut. Let’s draw the door again. It’s like this. Usually when we breatheout it’s like the door is hinged on something,it’s not going to close. The air rushing out, it’s pretty fast, there’s a lot of air becausethe walls are pushing it out. Imagine this is the amountof air that goes through. In emphysema with the doorunhinged and just flopping around in the wind it is less likelyto snap closed like that if there’s less air goingthrough and it’s going slower. That’s why people have figuredout that when you have COPD if you purse your lips and youbreath slower it keeps this airway open for just a littlelonger, and every second you can keep that door openis a tiny bit more air out. Let’s just put that down in writing here. We have the pursed lips,that’s the first thing. Now we have this slowing downof the speed of the air going through, because the pursedlips are trying to control it. But the rate of theirbreathing actually goes up, just because since they’rebreathing not so efficiently they compensate by breathingmore times per minute. This also contributes tothe fact that they look like they’re puffing andhuffing to other people. In a nutshell if I wereto describe what I think of emphysema as being inmy head it would be these dilated lungs, a big barrelchest, and this person breathing with pursedlips and they’re puffing.
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