Bronchiolitis diagnosis

- Now recall that if we break down the word bronchiolitis, we can get an idea of what the disease is. Now, the first part of the word is bronchiole, and in the respiratory tract, the bronchiole is the part of the airway that's further out. So we have the trachea, and then we have the bronchi. And then as we get further out, these tubes out here, these ones here are known as conducting bronchioles versus these small tubes all the way out by the alveoli that are known as respiratory bronchioles. But both of them are still bronchioles. And the -itis reminds us that this is inflammation of these bronchioles. And it can be of these respiratory bronchioles or of the conducting bronchioles. Now, how do we diagnose bronchiolitis? Well, before we make the diagnosis, what are the different diseases that we might be looking for so we can differentiate between them? Now, to get an idea of what a couple of these different conditions that are on our differential are, I wanted to just bring in this image of the respiratory tract so we can see where on the respiratory tract these different conditions are affecting. Now, since we're talking about bronchiolitis, it's going to be the first diagnosis on our differential. Now, bronchiolitis affects the bronchioles. So it makes sense that other conditions that affect this part of the respiratory tract, the airway, would cause similar symptoms. So a couple conditions that might cause disease here are things like asthma and allergic reactions. But sometimes diseases of the lung tissue itself can present similarly to diseases of the airway. Well, the one you should probably remember is pneumonia. And pneumonia is an infection of the alveoli, the part of the respiratory tract where air is exchanged between the environment and the body. Now, there's one other diagnosis I want to put on this differential, and this is a foreign body aspiration. So when a kid swallows something, let's say maybe a kernel of corn or something like that, it can get dislodged, and it causes blocking of these airways. And it can actually have symptoms that are very similar to bronchiolitis. All right, so now that we've established our differential diagnosis, how do we go about actually diagnosing bronchiolitis? Now, bronchiolitis is most commonly a clinical diagnosis. And this means that it can be diagnosed on the basis of history and physical examination alone. Now, there's a few historical components that are very characteristic to bronchiolitis, and one component is the age. So it's important to remember this because the majority of individuals who have bronchiolitis are under the age of two years old. And bronchiolitis also has very characteristic signs and symptoms. And these characteristic signs and symptoms are cough, rhinorrhea, or a runny nose, and wheezing. But you can't make the diagnosis on that alone. So what are some of the vital signs? The vitals in children with bronchiolitis can vary. A child doesn't necessarily have to have a certain set of vitals. These may or may not be present, but they may have a fever, and they may also have an increased heart rate. And one vital that some people don't always think about as a vital that I want to include here is oxygen saturation. And oxygen saturation is a marker of how well the body is able to put oxygen into the blood, how well the lungs are working. And since bronchiolitis is an infection of the respiratory tract, if it gets really severe, the child may not be able to oxygenate their blood well, and they'll have a decreased O2 sat. And so what are the characteristic physical exam findings? Bronchiolitis is inflammation of the bronchioles. Now, if we think of this in terms of the pathophysiology of what's going on, we can kind of determine what the physical exam findings are going to be. So let me just draw a picture of a bronchiole here. Now, if you think of this as the bronchiole, the airway, and it's cut in half here so you're looking down the tube, you can see this circle here represents the inside of the airway. If you think of this as a normal bronchiole, in bronchiolitis, you have inflammation. And so you get these walls become really inflamed, and you can tell that the airway becomes really narrow. It's much more narrow than it is in a patient without bronchiolitis. When this happens, the diameter of the airway decreases. So if this is a normal airway diameter, it goes down, and now we have a new airway diameter. Now, if you think about this airway, if you think about air rushing through the airway here, the airway's smaller. So that in order for the same amount of air to travel through this smaller, or this constricted airway, it's going to have to move a lot faster. And this produces a very characteristic finding known as wheezing. And wheezing can be heard with a stethoscope on the chest, and it sounds like a high-pitched musical sound that's typically heard during expiration. So here's an example of what a wheeze sounds like. (muffled breathing) All right, so here, that's our characteristic finding on physical exam. But what are some of the other findings? You might have signs and symptoms of respiratory distress, and the child might be breathing faster than normal. So we'll just call this increased work of breathing, and I'll abbreviate that as WOB for work of breathing. And these are the really characteristic physical exam findings. But there are some additional tests that are sometimes done to aid the diagnosis of bronchiolitis. Now, it's important to know since bronchiolitis can be a clinical diagnosis, these tests are not routinely performed. And so if they're not routinely performed, why would a provider order one of these tests? And that would be to rule out one of the other diseases on your differential. Now, the first test I want to mention is a nasal swab. Now, a nasal swab is just what it sounds like. You use a cotton-tipped applicator to swab the nasal cavity, and it picks up maybe some nasal secretions here. We'll kind of have them dripping off this cotton swab, so you're reminded there's some nasal secretions here that you get on it. And these nasal secretions can be tested for viral material. And the two types of tests that are generally performed are nucleic acid amplification test, also known as NAAT, or polymerase chain reaction, also known as PCR. Now, these tests will tell you whether or not the virus is present in the oral pharynx, but it doesn't have a whole lot of clinical utility. It doesn't necessarily change how a provider is going to treat the child with bronchiolitis. Now, the other test I want to mention is a chest X-ray. Now, before we take a look at a chest X-ray, I want to draw out a couple diagrams here so we can get an idea of what findings we can expect to see before we actually see them. Now, I'm going to draw another bronchiole here just like I drew to help understand wheezing. Now, let's cut this bronchiole in half right here, and we're going to look at a cross-section of it. Now, a normal bronchiole has a thin wall, and this thin wall is not visible on an X-ray. But like before, in bronchiolitis there's a lot of infection that makes this airway a lot narrower, and it makes the bronchiolar wall very prominent. And not only is there inflammation in just the bronchiolar wall, it kind of causes some in the tissue surrounding the bronchiole. And all this inflammation is visible on a chest X-ray. So if the plane of the X-ray happens to catch a bronchiole on cross-section, what you're going to see is kind of a little circle. And this finding is known as peribronchialar cuffing. Now, to give you an idea of the other characteristic finding, I'm going to draw a cartoon of some lungs here. Now, in this cartoon, we have the airways here, and we have the lung tissue themselves. And in bronchiolitis, we get inflammation of these bronchioles, right? It's all inflamed. Do it over here too, lots of inflammation. And so the airways here are very narrow, which is what we can see right here. Now, when we're breathing in, air is able to get through these airways. But when you breathe out, it actually has a hard time coming out. It doesn't really come out, and so air gets trapped in these lungs. So let's see how this looks over time. So you can see that as the air comes into the lungs and it's not able to get back out, that that air then stays there, and that causes the lungs to expand. And then as you breathe in on the second breath, the lungs, once again, fill with air, and they get even bigger, but you can't breathe it out. And so over time, the lungs just keep getting bigger and bigger, and this is known as air trapping. And it's sometimes also referred to as hyperinflation. Now, what does this all look like on an X-ray? Now let me first just orient you to this image. You have the trachea, or the respiratory airway coming in here, and it's a little bit darker shadow right there. And it comes down, and it branches out on both sides here into the bronchi, and it comes out to the lungs. And these kind of shadowed areas along here are the lungs. And this kind of ball-shaped thing in the center, that's the heart. And this area here, actually this kind of looks like similar to the lung up here, this is actually the stomach. And you can tell the difference here because there's this almost dome-shaped line in between, and this dome-shaped line is the diaphragm. And the diaphragm is a muscle that helps your lungs expand and allows you to breathe. Now, let's first talk about the peribronchialar cuffing. Now remember, that's going to kind of look like a circle, or some people describe it as maybe a Cheerio-look on the X-ray. Now, if you look closely, there's a few of them on this chest X-ray, but they're kind of hard to see. Now, one of them is right here. Now look closely, you can kind of see a circle of white with a little dark spot in the middle. Now, let me just kind of highlight it here for you. So you can imagine that one here. And now as I highlight this one, you can kind of start to see another one right above it if you look really hard. So let me highlight that one too, all right? And now once you start to see them, they kind of pop up everywhere. Once you see one, you start to see a lot of them. So there's another one here, and there's another one way out here in the periphery of the lung. There's a couple more here, and up here, and here. So these findings are called peribronchialar cuffing, and they're characteristic of bronchiolitis. Now, the other finding, the air trapping, is not quite as evident on this chest X-ray. And air trapping, one of the best ways to look for it is to look at the diaphragm. So remember I mentioned this dome-shaped line here? That outlines the diaphragm. So let me just outline it here. Now, if the lungs become hyperexpanded, this diaphragm is flexible. And it actually be pushed downwards, and you can have flattening of the diaphragm, something that looks like this. So if you see a diaphragm that's been pushed down because the lungs are becoming hyperexpanded, that's then seen on a chest X-ray as kind of a flattened-looking diaphragm. And again, that's not exactly evident on this chest X-ray, but that's another finding that's very characteristic for bronchiolitis. So if you can remember that bronchiolitis is the most common respiratory infection in children under the age of two years old, and that it typically presents with a cough and runny nose, and if you take your stethoscope and listen to their chest, and you hear wheezing, chances are you just diagnosed bronchiolitis.