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I'm Dr. Ravi Kalhan, pulmonologist at Northwestern Medicine. I'm here today to answer your questions from the internet. This is Lung Support. A Reddit user asks, "Why are we able to breathe both consciously and automatically?" This is super interesting and unique to the lungs because no other organ can you consciously control it. You can't make your kidneys filter more fluid. You can't really just make your heart start beating faster. You can't make digestion speed up. There's no other organ that can do this. But for the lungs, it's essential. So the brainstem, the oldest part of the brain in terms of
evolutionary terms, controls breathing automatically. And respiration just happens. The brainstem makes sure that the diaphragm keeps contracting, the lungs keep filling with air, and you keep breathing. That's super important cuz otherwise every time you went to sleep, you'd die, right? But we also need to talk and laugh and scream and sing. So the conscious part of the brain, the cortex, can actually control breathing in addition to the brainstem. So in that sense, we can both manually control our breathing as well as have automatic functions that keep us alive. Purest videos asks, "How exactly do asthma inhalers work?" Well, asthma inhalers contain medicine. It actually
drives me crazy when people only refer to it as an inhaler cuz it's a medication. And they're medicines that we can deliver straight to the windpipes. The problem in asthma is the windpipes are over inflamed because a person is susceptible to things in the environment like pollen, pollution, or if someone smokes cigarettes, that cause inflammation in the windpipes. So the way we treat that is with inhaled anti-inflammatory medicine. Usually that's inhaled steroids. You can inhale corticosteroids that treat the surface of the windpipes so that they get less inflammation because of those corticosteroids anti-inflammatory effects, and then the lungs don't have that inflammation and
people have less asthma symptoms. Asthma inhalers also often have a bronchodilator. Those medicines relax the muscle surrounding the windpipe so that the windpipe can open up and air can move in and out more efficiently. I is smarter asks, "What actually happens when you get the wind knocked out of you?" Well, when the wind gets knocked out of you, it usually comes after someone gets hit in the chest or punched in the gut. And that's not actually a problem of the lungs. It's a problem of the diaphragm where getting hit right here, sort of like where the ribs come together, there's a nerve bundle right there called the solar plexus, which is not that protected by bones. It's like
right in that open space behind your stomach. And when you get hit there, the thought behind the wind getting knocked out of you is the diaphragm goes into spasm. So the diaphragm doesn't work right. You feel like you can't breathe cuz the diaphragm's not moving down. And then it takes like 30 seconds for everything to reset, calm down, the diaphragm to relax, and for the person to recover after getting the wind knocked out of them. One user asks, "Why do humans have two lungs instead of one single big lung?" It's probably the result of evolution deciding to having two things or redundancy is better than having one thing. It's like why does a airplane have two engines instead of
one? Well, that's because if one goes down, the other still works. Akidae asks, "Does this sound like COPD?" This doesn't sound like COPD because COPD usually is characterized by having less sound in your chest. COPD stands for chronic obstructive pulmonary disease. It also gets called emphysema. So normally the lung is like rubbery and elastic, like a balloon. And if you blow air into it and it's inflated, you take a big breath in and let it go, the air [snorts] just comes out super fast. When someone has emphysema, the lung is not rubbery anymore like a balloon. It's like a plastic grocery bag. You blow air into it and the air just kind of sits there and floats and the air doesn't come out. And we normally hear less sounds in the
lung, not more sounds in the lung. With a bag asks, "How TF does a lung transplant work? Like how do they get the lungs out?" In the old days, we actually used to just take the lungs out by creating a giant incision in the chest, opening it up, deflating the lungs, and taking them out. When they deflate, they're actually pretty small, like the size of your fist. So these days, there's all kinds of new ways that they're doing transplants that make it easier to tolerate the surgery. So the lung only actually has three connections to the body. They're connected through a windpipe, through a vein, which takes blood from the lungs to the heart, and an artery, which brings blood from the heart to the lungs. Just those three
hookups. So if you can remove those three hookups and deflate the lung, you can actually take it out through a smaller incision. So that's what's going on now at a lot of places that they're doing smaller incisions, sort of between ribs, where they can take the lung out and then put a new lung in. The way people live during that period is they're put on a bypass machine, which does the oxygen and gas exchange for the person while their lungs are going in and out of the body. But the manner in which the transplant takes place at a lot of places is a lot less sort of dramatic, what we used to call a clamshell, sort of just cut open and lift up the chest.
Now there are a lot of smaller ways to do it cuz the lungs can deflate and reinflate once they're in the body. Andre the Boss 21 asks, "Did you know that we still don't know why we yawn and why it's contagious even across species?" There are some theories about why people yawn. One of them is debunked, that the brain or the body needs more oxygen. That's not why people yawn. The current most talked about theory is people yawn because it increases blood flow to the brain and cools it down. So it's like a cooling function for the brain. Why the brain needs cooling, I don't think we know. Why yawning is contagious, some people think is like a old social network thing of empathy that gets transmitted sort of naturally in
the human state. Because yawning is considered sort of this empathetic social response to people around them, it takes time to develop that empathy. And 4- and 5-year-olds, in general, don't have contagious yawning cuz they haven't developed those empathetic networks, or so the theory goes. A Reddit user asks, "How does air enter the lungs?" Well, this is an interesting question because while one might think air gets sucked into the lungs, it's actually a completely passive process. There's a muscle below the lungs called the diaphragm, which is dome-shaped. When you breathe in, that dome flattens and the lungs have negative pressure in them compared to what's in the atmosphere. Air always flows from higher
pressure areas to lower pressure areas. So when the dome flattens and there's negative pressure inside the chest, air enters the chest. How does air leave the chest then? Well, the lungs always want to deflate. They're filled with air and they're like a rubbery balloon. So after that negative pressure fills the lungs, the diaphragm relaxes and air's natural tendency is to come out because the lungs are elastic and rubbery. Troll girl 666 asks, "WTF are hiccups? For like why am I being punished for breathing?" Well, a hiccup is a pretty weird thing. It is when the diaphragm tries to breathe, but then the vocal cords prevent the breath from happening. And there's like this awkward feeling of where air's
trying to go in, but then it gets cut off up here by the vocal cords. And no one knows why they happen. They could be because something irritates the diaphragm. They could be because something irritates the vocal cords. Like sometimes people say they drank too much carbonation and they start hiccuping. There's no real knowledge for why that reflex exists. It's probably related to some ancient reflex that developed over time during evolution. But they certainly are uncomfortable. Burkin8000 asks, "What chemicals actually make vaping dangerous?" There are a lot of chemicals in vape juice that we don't know all the time how dangerous they are, but it stands to reason that they probably are. The first
big one is if someone's vaping nicotine, there's nicotine in the vape juice. At high levels, actually, it gets heated up in the juice and aerosolized, and then you can breathe it in. And that's a high concentration of nicotine, which creates addiction. Nicotine is a highly addictive chemical. How dangerous that nicotine is on a day-over-day basis is not totally clear, but being addicted to it creates problems and desire for more and more nicotine. There are other chemicals in vape juice that get heated up. For example, there's formaldehyde. The stuff used to preserve bodies is in vape juice. And heating that up and inhaling it, well, that probably isn't that good for you in the long run. There
are other things like there's flavors, and these are food-safe flavors in vape juice. So you use fruity flavor vape or peppermint or whatever the vape is. They're probably okay to eat, but we don't know what happens when you heat them up, turn them into a volatile substance, and inhale it in the lungs. That could be really dangerous. So all these things, you know, are, in my mind as a pulmonologist, bad for you. I think, as a lung doctor, the thing you're supposed to inhale is air. Gandhi's account asks, "Why does exhaling after you've held your breath for a long time feel like you're not suffocating?" Well, when you hold your
breath, you take a big breath in and hold your breath, you're not breathing. And when you're not breathing, the body does not release carbon dioxide. It also doesn't inhale oxygen, but in the sense of suffocating, the carbon dioxide is what matters. So, when you don't exhale carbon dioxide, it builds up in your blood. Carbon dioxide is an acid, so the pH in your blood goes down. There are receptors in your bloodstream that feed into the brainstem and create a sense of needing to breathe when the pH in the blood goes down because of this increase in carbon dioxide. So, that's when the brainstem kicks in and says, "Dude, we better breathe right now." So, the sense of relief that comes when you finally start breathing and feel like
you're not suffocating anymore is because you finally are releasing that carbon dioxide. The pH in the blood is going back to normal and the satisfaction of being able to breathe again kicks in. Rateo BC asks, "What's the difference between breathing in through your nose and mouth and why it's recommended to do it through your nose?" When you breathe through your nose, a lot of good things happen. The nose filters air. There's hair in your nose, it's a first line of filtering, and then there's other filtering steps through what are called ciliated epithelia. There are cells in the entire respiratory tract that have little flapper things on it that can move debris and other mucus out of the way so that air can go through more smoothly.
When you breathe through the nose, the air also gets warmed up and humidified, so that's good. And then the third thing, which people don't actually know that commonly is the sinuses produce something called nitric oxide. Nitric oxide is what's called a vasodilator. And when nitric oxide comes into contact with the lungs, it helps ensure that where air goes, cuz there's nitric oxide there, the blood also goes because it opens up blood vessels. So, then we have a really good matching between where the oxygen goes and where the blood goes, so oxygen can more efficiently enter the bloodstream. So, those are all benefits of breathing through the nose. If you breathe through the mouth, those things
don't happen. There's no humidifying, there's no clearance, there's no nitric oxide. But what there is less resistance to airflow. So, when you're exercising and you need to get air in and out really efficiently, you shouldn't breathe through your nose. You should do the natural thing, which is breathe through your mouth. But when you're just at rest or not doing anything that involves exertion, there are clear advantages for why breathing through your nose is better. @10 CO asks, "Why after running for a while do my lungs get that painful burning sensation?" It's actually not your lungs. The lungs don't have pain receptors. The windpipes do, however. And when you exercise, you inhale mostly through your mouth. So, all the good
stuff that happens when you breathe through your nose, humidification of the air, warming of the air, cleaning of the air, doesn't happen and everything goes sort of straight in through the mouth. So, if it's cold outside, this symptom might get worse because it irritates the windpipes when you breathe in cold air through your mouth. Google Bro asks, "Coughing up mucus with blood, should I be worried?" I think you should be worried. Anyone who coughs up blood should see a doctor ASAP. Rachel Bunny asks, "Why does breathing into a paper bag help with hyperventilating?" One could wonder why someone hyperventilates in the first place. Well, it could be caused by lots of things. The biggest
thing is anxiety or distress or panic. Those are the things that we treat with a paper bag. When someone hyperventilates, they have lowered the amount of carbon dioxide in their blood. It actually turns out that those people who are hyperventilating have normal oxygen levels. It's all an ability to lower their carbon dioxide when they start breathing really fast. So, that makes you feel kind of funny and unsettled. Having a high pH creates a sense of further anxiety, maybe tingling in the fingertips, all sorts of weird things that go on when someone hyperventilates. If you start breathing into a bag, however, when you hyperventilate, the carbon dioxide you breathe out gets stored in the bag cuz
you're sort of pinching it and breathing in the bag like this. So, you start rebreathing carbon dioxide, which naturally makes the carbon dioxide level in the blood go up again, so the pH goes down, the blood becomes more acidic or gets closer to normal, and it relieves the sense that you get when you're hyperventilating that everything is going wrong. A Reddit user asks, "What happens to food that accidentally gets in the lungs?" The first thing that probably happens is you start coughing a ton because the body has a defense mechanism. If something that's not supposed to hit the vocal cords or the main windpipe up here, the trachea, if something hits that, there are very, very sensitive cough receptors
there that make someone start coughing like crazy and the food never makes it down further. If the food does make it down further, like a tiny amount of food gets down further, the body has defense mechanisms for that. One of the biggest defense mechanisms is that there are cells in the lungs that are called macrophages that will surround that thing and start to sort of degrade it or take it up so that it can't cause problems. Don't Spill Me asks, "What is going on when a lung collapses?" Normally, the lung stays inflated only because of a suction effect of the lung against the chest wall. There's just like a thin layer of fluid between the lung and the chest wall and the lung is kind of just
suspended there. You know, if you have a glass and it's condensing cuz you have ice cubes in it and it's on a counter, the glass kind of sticks to the counter because of that fluid between the glass and the counter. That's what's going on with the lung. It stays inflated because of that fluid. So, if something disrupts that layer or if the lung gets punctured for some reason, so there's now air between the lung and the chest wall instead of fluid, the lung will actually collapse because it can't stay inflated. The lung is rubbery and elastic. It's only staying there cuz of that suction effect. So, when the lung collapses, the way to treat it is to insert something called a chest tube where we stick a
tube from the outside through between the ribs into that space between the lung and the chest wall and suck out the air that got in there or whatever else is in there. Sometimes an infection can occur in there, sometimes blood can end up in there. Suck that out, so then the body can heal, restore that little fluid layer, and then the lung can stay inflated again. A Reddit user asks, "How do the lungs heal after a smoker quits?" This is a great question cuz I think every smoker should quit and it's true that a lot of the lung can heal. Most of that healing happens in the windpipes, which are irritated by smoking cigarettes. So, normally the lungs have a defense mechanism called the
mucociliary escalator, which is the flapping of these things called cilia at the tops of the cells that line the windpipes. So, when you breathe something in that's toxic, the cilia kind of can flap it back up. So, if you inhale small particles from cigarette smoke, the cilia can help clear things out or if the lungs produce too much mucus cuz they're irritated, the cilia can kind of flop it back up to your mouth and you swallow it and it goes to your stomach where it doesn't cause any harm. One of the biggest bad effects of cigarette smoking is that it impairs the function of this mucociliary escalator and actually causes the cilia to disappear. So, there's no defense when someone smokes cigarettes. When they quit
smoking, that function starts to return over a month or so. So, a lot of people when they quit smoking say, "Oh my gosh, I quit smoking and I'm coughing up all this mucus now." Well, that's because the defense mechanisms that help you clear out mucus are actually working again. That's a positive sign. @BRoosterMaster asks, "Every time I cough, a little chunk of my lung comes up. Is this normal? Do lungs grow back?" Well, it's pretty unlikely that's actually a chunk of your lung coming up. It's pretty hard to cough up a chunk of lung. I don't think that actually happens. It's probably mucus that's coming up that looks pink, maybe cuz there's a little bit of
blood in it, but it's not actually your lung. Fever Coach Admin asks, "Asthma versus pneumonia, how do lung sounds differ?" Here's the sound of pneumonia. So, in that clip, someone is talking or whispering while they have pneumonia. And when someone has consolidated pneumonia, pneumonia's when part of the lung fills up with infection or something else. So, like on this X-ray, you can see the normal lung is dark and black and filled with air, and then there's this top part here, which is white, which means it's filled with something. When the lung consolidates, it can suddenly transmit sounds much better than if it's filled with air. So, if the lung is filled with air and you whisper and I listen with the stethoscope right on
that spot, I won't hear you whispering. But if it gets consolidated or filled with fluid, suddenly it can conduct what is being said at the vocal cords. So, if someone whispers then, you can actually hear the whispering is sort of a vibrating sound when you listen over that part of the lung. Now, we can listen to what asthma sounds like. Asthma, in contrast, is a problem of the windpipes, the pipes that lead to those air going in and out of the lungs in a much more prominent way than we do if someone doesn't have asthma. So, we hear squeaking or wheezing or various things like that make noise of air going out of the lungs that we normally would not hear as a squeaking high-pitched
noise. I promise to shut up asks, how does oxygen go from lungs into blood? Could you explain in details and simply? Well, when you breathe in, oxygen enters the lungs and the air has 21% oxygen. The lungs are comprised of millions of tiny air sacs that inflate when you breathe in. The air sac is called an alveolus and it's surrounded by a net of alveolar capillaries, which carry blood from the heart past the air sacs and they form kind of like a net, a mesh around the air sacs. In between the capillaries and the air sac is a super thin membrane, like a microscopic filter. So, when you breathe air in, it's just a matter of diffusion. The 21% oxygen that you breathe in is higher
than what's in the blood that returns to the lungs from the rest of the body. Because there's more oxygen in the air sac than in the blood that comes by the air sac, that oxygen diffuses across that alveolar membrane into the blood. Once the oxygen hits the blood, there's a molecule in the blood called hemoglobin, which is highly avid for oxygen. So, the oxygen molecules attach to that hemoglobin and it gets carried away back to the rest of the body which needs the oxygen. All right, well, that's all the questions I got today about your lungs. Hope you learned something.
