What is asthma?

- [Voiceover] When I first started thinking about this video, I realized that asthma is going to be hard to talk about because so many people have it, everybody knows at least a little bit about it, so it might be hard to get really to the bottom of what really is asthma. So, to do this, let's go all the way back from the beginning. Let's just start by talking about the lungs, and what they look like and what they do. So, we have here your big trachea, and they branch off into your left and right bronchi. Those are the two main stems of the lungs. And from there, they keep branching off like branches on a tree, and they get smaller and smaller. There are countless levels. I'm gonna just try to draw a few levels here for us. So they keep branching off like this, you get the idea. When we inspire, or when we breathe in, inhaling, it's kind of like a vacuum cleaner sucking air in. And these are all the tubes that are connected to it. So this is like the big hose. If you can imagine your vacuum breaks down into little hoses, that's basically what it looks like. So in our lungs oxygen goes in, when we breathe in. O2 is oxygen, two oxygens. And then on the reverse side when we breathe out, we breathe out carbon dioxide, which is the symbol as CO2, one carbon and two oxygens. Now asthma is classified as an obstructive disease where air is blocked on the way out, breathing out CO2. But we'll get to that later exactly where that happens. For now if we are just looking at the set of tubes, otherwise known as our airway, and anywhere we go, if we take a cut like this across any of the tubes and we look at it up the tube, or we look at what is called a cross section of it, then it's going to look something like this. So we have a round shape for the outside of the tube. And then we have an opening. And in the middle here we call it the lumen. The lumen is just the inside of any tube. This is where air actually goes through. And here in the walls of the airway, we have connective tissue, we have glands, we have all kinds of things. But I want to talk about this smooth muscle layer here that's around in the wall of the airway. So since it's a muscle, then it can have force and change the shape of things around it. So in asthma, what we care about is that the smooth muscles can actually constrict this airway. So to see what that looks like, let me draw this again here. Again, if this is the outside of the wall, then a person who has active asthma happening at the moment, their airway's going to be smaller, the lumen is going to be smaller, maybe about, let's say this big. And what has happened, is that the smooth muscle around it is contracting hard and is clamping down on that lumen. To make matters even worse, when our body's inflamed, it secretes fluid. So into the lumen, which is usually supposed to be open and dry, we have extra fluid. So when the opening is already smaller, it's being flooded by mucous and fluid. And this whole picture together is what asthma looks like in our airways. Now I just showed you one tube here, because we cut it once here. But imagine this process is happening in all these vacuum tubes, all these little levels. So the air is really having trouble moving. Actually, if you could imagine a vacuum. Let me just draw one here. This is the very primitive model of our vacuum. And if you could imagine that this machine has a lot of power sucking air in, but when it's coming out, it's a passive process, so there's no power pushing the air out. So even though this constriction here will make it harder to suck air in, but at least it has a motor behind it, as opposed to when the air's coming out, it just has to passively leave through the smaller straws. So that makes it harder on the exhale. We'll come back to what that sounds like when we listen with the stethoscope. But first, let's talk about what causes this process. Why would your airway suddenly clamp down like that? Why would our body allow it, and what triggers it? So I promise that every time I talk about lungs, the first thing I will always say is, smoking. Smoking can be a huge trigger for asthma. Doesn't even have to be firsthand smoke, it can be secondhand. In fact, kids who have asthma, they're exposed to parents who smoke in the house. Even parents who are smoking outside, but then wear the same clothes inside the house. That can trigger asthma, because these smoke particles are billions and billions of little things that don't belong in the lungs, and when they're in there, this process can happen. Also because we live in a time where there's so much machinery around us, this is a car if you can tell... So car exhaust and pollution in general in the cities can be a huge trigger for asthma. Also people whose jobs expose them to things like asbestos, or other things they can inhale can be a trigger. I'm just gonna start writing cause I can't draw fast enough. We have paint, remember that everybody has different triggers. People who have asthma don't react the same way to the same things. And this one, I think, is really sad. Some people can be triggered by food. You can be allergic to foods. Or things in beer or wine, can trigger asthma in some people. Now another trigger can be as common as stress. Our body reacts to stress in a variety of ways. It can increase inflammation, which asthma is basically an inflammatory process. So this one I think is interesting. A common drug that most of us have probably taken, can be be a trigger in up to 30 percent of adults who take this drug, and that is aspirin. Helps with your headaches, but sometimes causes your asthma to flare up. And lastly, babies who are completely different creatures from adults, they can have GI reflux, or what we call heartburn, where the things in their stomach go back up the esophagus. Since they are so small, their system is so close together, it can go up the esophagus and into the trachea. So they can be triggered by GI reflux. As you can see, this reaches almost every aspect of life, this is probably why so many people have asthma, and it's so different in everyone. So going back to our kind of clinical, medical way of thinking of asthma, if you are going to listen to a person breathe through your stethoscope, and this person has asthma, what might that sound like? Let me draw a stethoscope. Are we gonna listen to these lungs? Now keep in mind, as I said earlier, there is fluid in here as well, so these smooth muscles constrict, but there's also fluid and mucous getting secreted into these tubes as part of our body's way of dealing with inflammation. So air and fluid together, what do they form? They form air bubbles. So as these air bubbles pop and reform, and we're trying to breathe through them, that's why we would listen. We hear a high-pitched noise that's referred to as wheezing. Now wheezing is very characteristic of obstructive diseases, like asthma. Wheezing basically sounds like a tiny little whistle, so when they inhale and then exhale, on the exhale you hear high-pitched noise all over the lung fields. Now I'm going to draw an imaginary line that divides our lung here. So the trachea, this is called the upper airway, and down here are the smaller airways. A wheezing in asthma is a small airway disease. It is a small airway disease that happens on the expiration, or when you breathe out. Now if there's noise on the inspiration, that's usually caused by a foreign body, or some other kind of process that makes the upper airway constrict. That doesn't really happen with asthma unless it's super severe, and this person is just dying for breath. So usually asthma you can get an air in, and it's on the expiration that we have a problem and you hear the wheezing. Because again, the vacuum is sucking in air in the inspiration, so it's going okay. But when you breathe out, passively, the restriction really causes a problem. So remember: asthma, wheezing, small airway disease. Now this next part... I don't have asthma, so I always feel like I'm not such a good judge on what it really feels like to have asthma. But we can imagine that if this person has trouble breathing out, breathing out is just as important as breathing in, if you can't do either it's a very scary process. And this person coming in will be complaining of shortness of breath, so shortness-of-breath. SOB is a very commonly used way to describe the symptom of can't catch your breath, panting, shortness of breath. Now depending on how severe their attack is in the moment, a lot of people have rescue inhalers. When they're panicking and can't breathe, this rescue inhaler can deliver some emergency drugs to open up that airway. And it's such an important intervention for people who have asthma to not only breathe, but to feel like they can breathe, to help with the panic and just the discomfort of not being able to get a breath in and out. Now lastly, I just want to mention that asthma, just from observation, seems to be related to two other diseases. There's asthma, there's eczema, which is a disease of the skin. You have excessively dry patches of skin that, again, flares up. It can be red-angry or dry and peely, a skin disease. And then the third, we have allergies, or some people call it allergic rhinitis, which is more proper for (mumbling) your nose, rhinitis. But most people are just calling it allergies. And these three things, for some reason seem to be good friends, in that a person who has one, is likely to have the other two. We don't really don't know why. We're still studying why that relationship exists, but it does, especially in children. So this in a nutshell from a thousand miles above, is what asthma looks like, what it is. So just a few key words to remember. We have airway constriction, in the small airway that causes shortness of breath and sounds like wheezing on a stethoscope.