[MUSIC] If there are no questions, I will then turn it over to Dr. Lance, would you like to introduce yourself? >> Sure, hi I'm Dr. Rachel Lance, but you can just call me Rachel Duke automatically puts the full thing on the Zoom account for me, but I tend to be a pretty casual person. I have a PhD from Duke in biomedical engineering and that's a fairly broad topic in general. But I specifically said specialized in patterns of injury and trauma, especially physiology and survival in extreme environments. So that makes it a little bit clear how I started to get involved with this course. But a lot of my personal research background spans a broad variety of topics because a lot of them tend to have overlapped. So when you're talking about extreme environments especially like outer space, they tend to have a lot of things in common with some of the other types of extreme environments like underwater or. One of my particular passions of science is blast trauma. And the reason those things are all linked together is because they all have this immediate and severe impact on the human looks, which obviously are pretty key to survival. So one of the things that I do it, Duke is I do a lot of research at the hyperbaric chamber where I understand there's been some footage taken for this course. But I work there where we simulate extreme environments of different kinds either high-pressure or low pressure. We can immerse people in ice water, we can control the temperature may get warmer, we can give them exercise tasking. We sometimes will give them different gasses to breathe and all of this is with the goals, looking at the physiology of how their bodies respond to these environments. And of course with the ultimate goal of keeping our real life explorers safer and helping them to do more real life exploration in a safe way. That helps too where they can actually survive and also then come home safely. >> I think just recently you guys had astronauts come to the chambers, is that, right? >> Yes, that is one of the things we do at the chamber of recently, we had the four crew members of the upcoming SpaceX mission. Yes, someone typed inspiration for into the chat, that is correct. So it's the crew members of the upcoming SpaceX inspiration for mission which is supposed to launch in September and the reason that they came to the chamber was for hypoxia training. So obviously one of the big issues of surviving outer space is that there's not a lot of gas out there. So that creates a problem and a challenge in terms of breathing, yeah, hypoxia in particular can be a particularly noxious ailment. Because what ends up happening is as the oxygen levels lower in the bloodstream, people tend to just gradually lose cognition and they tend to gradually lose function. So you would think that would be very aware of that as you would slow down and slow down your processes. But unless people have gone through specific training where they felt this experience, they understand what it's like, then they tend to actually just sort of pass out, that's obviously a really bad scenario. It's bad enough if you're in a hospital, but it's even worse if you're in outer space when it happens. So the reason that the crew and they're physiologists, excuse me of physicians came along to do who is so that we could take the chamber of the high altitude. So we ran what's called the hypoxia training protocol on them. We put them in the chamber and we picked them up to 25,000 ft of altitude and then I got to take away their oxygen. So technically I got to suffocate a bunch of astronauts and I got paid to do it, which is a pretty unique life experience for me. But basically what happens then is to give them cognition tests which can vary in format, but usually they're written test. So you have some kind of souvenir to show yourself later just how drunk you were on your lack of oxygen. So 25,000 ft is an altitude where people can survive Mount Everest is I believe 27,000 and change, but usually they're only up there once they've had time to activate. So those people when they're going to those altitudes will have time where they're at base camp. And they'll have time for their bodies to adapt to the high altitudes by creating more red blood cells to help increase Their ability to transport oxygen. So if people come to the chamber we take them up to 25,000, we take away their oxygen Dermot. Hat they do not have that opportunity to make those red blood cells, They can't do it quickly enough. And so they end up having just a gradual decline in function until they have pretty much total loss of cognition and control. So that was a pretty interesting day because I gave my astronauts connect the dot drawings and they all failed at the chicken. [LAUGH] They got to that chicken on the last page and they all just got completely stymied by it. So you can really watch them starting to struggle with the lack of oxygen. And that also gave them an understanding of if I'm having this difficult of a time, cognitively processing, my brain should go into autopilot and understand this is probably hypoxia. There's something probably wrong with my breathing gas and then that gives them the ability to better address that situation. >> Fantastic, And then Zoo ask the good question that I think is a good follow up for that is for the physicians and researchers that are working in these conditions. How do they not succumb to either the highs and the lows and the effects of that pressure, right? If you're a doctor working with a patient in the hyperbaric chamber, how does someone not get affected by the change in the artificial atmosphere? >> Yes, great question, so the hyperbaric chambers have breathing systems built into them. So we can provide people gas with either of two ways. Either we flood the entire chamber with a gap whatever gas mixture we want, in which case everyone gets the same dosage or we have individual breathing masks. So there they are actually the exact same maps that are used by aviators and fighter pilots is the best description. And we have those masks and then you can individualize who is getting what type of air. So for example, for those trials, when we were in the room, all of the people who are administering the tests simply cut their masks on and the master delivering 100% oxygen. Whereas the people who were experiencing the hypoxia and we're being supervised, we took their masks off. So they were getting room air, which is 79% nitrogen and 21% oxygen. So being cut down to 1/5 of their oxygen supply was enough to cause that loss of cognitive. Whereas the rest of us were kept safe because we were still on 100% 02, so we were still able to function. And then for those of you in the chat that are interested in those cognitive tests, Dr. Lance, I don't know if you had Hayley, I'm going to go to the pronunciation of the last thing but are. >> Arsenal yes. >> As part of your assessment of tests. But she had posted a photo of her kind of sequential numbers sheet on twitter. So I linked her tweet there in the chat. You can see what does this look like. Yeah, so that was one of the tests that we administered, my people got connected dot drawings and then she was one of the people who was asked to count down from 1000. And so you can see the time course there how your body starts out with an oxygen reserve. And then as you continuing to use oxygen at a normal rate, but you're not able to breathe in oxygen at a rate to replenish that you kind of start to lose function and lose documents. So someone also asked if the doctors were special suits so they aren't affected by the difference in pressure. So hopefully I answered that with my question about the fact that we're getting different breathing gasses. But the interesting part about the human body is that you really don't need a special suit for most of the other types of pressure differentials. Obviously a vacuum is a really extreme case, but in general the human body because it's mostly water and water is largely in compressible. Meaning it doesn't really expand or contract in response to pressure your body itself except for the lungs is not really going to have a lot of material changes in terms of lowering of pressure in general. It's pretty neat, yeah, so one of the other things, have you guys talked about hypercapnia yet? >> No, we have not, that is a topic, we're like, you know like it's definitely a I would consider as a basic EMT a high level EMT topic and you know like this outside the scope of the course. But yeah let's talk about it. >> Okay I can't talk about him because I personally think it's fascinating, obviously I'm very biased because I'm obsessed with the human look. But hypercapnia I think there's a really interesting topic because it's something that people all think is really obvious once they know. And they're starting to think about it and be aware of it but they don't necessarily see it coming unless they have some experience with breathing. So hypercapnia basically just means high carbon dioxide hyper meaning high and cop and coming from the carbon dioxide aspect of it and you can get high carbon dioxide from several different sources. So you can either be breathing a gas with high carbon dioxide or you can have impaired breathing function either way your tissues in your body are still going to be converting that oxygen. There still be using up that oxygen, and carbon dioxide is the waste product that they make. So what I think is really fascinating about hypercapnia is when that carbon dioxide starts to build up in your bloodstream it's actually stored in there as one chemical. And then there's a little hydrogen eyeing that's released as well, so basically the more part and hydrogen ions are what make up acid. So basically the more carbon dioxide that you get into your bloodstream, the more acidic your blood itself becomes. And the reason that's important is because then you kind of start to ceviche yourself right? Like ceviche is the concept that fish and tissues can be cooked by the presence of acid alone. And so your body starts to have really negative response, when you start to build an asset. It's normally a thing that we can physiologically control will control by breathing more, and so you start to hyperventilate. And the reason that hypercapnia can be such a problem is because when people are in an enclosed small space. They often think about the oxygen and they remember the oxygen and the importance of oxygen to breathing, but we actually end up in enclosed spaces. Like for example in a spaceship, if something fails in the breathing system, we end up having problems with hypercapnia first. Because you will exhale carbon dioxide at a rate where you're going to have problems from that long prior to you when you're going to have problems from low oxygen. I'm glad someone likes my analogy of ceviche, good job, [LAUGH] good job, but so anyway, that creates a lot of physiological issues. But the reason that we talk about it less often is that it's very easy to detect, so that was another thing that the astronauts citizen making the duke. And that's also a very common part of astronaut training in general, especially with NASA is we will have people breathe on a new clothes bag of air. Obviously these are always medical supervision but they breathe through an enclosed bag of air and they let we let the carbon dioxide that they exhale start to build up in that bag on its own. And so we don't have to introduce any carbon dioxide, they're going to start having problems just from their own exhaled breath alone. And so that's kind of a real life demonstration of how bad this hypercapnia can get and how it can create problematic symptoms. The symptoms, people will feel very a lot based on individuals, but they can involve like tingling in the fingertips. They can involve nausea, they can involve headache, speak to involve visual disturbances. Everyone reacts like in a slightly different way, which makes it kind of an interesting an interesting grab bag of surprises to happen. But basically everyone will have some sort of symptoms in general. And I think that's something that's really important to keep in mind when you're talking about breathing and when you're talking about extreme environments. Because most people think that as long as you have enough oxygen then you're fine, and that's really not the case. So that was actually one of the ways that I kind of got involved with doing more research of the chamber was actually started out researching hypercar apnea. Because my background is as an engineer with the US Navy, so I started out as a mechanical engineer designing breathing systems there. And we were constantly looking what happens with carbon dioxide building up in small spaces, which is kind of how I started a big submarine project. So this is a model submarine behind me, it's not really related to outer space, but this is my zoom corner. So, but it's one of the issues that shared inside both submarines and inside space shuttles. If you have a failure of the breathing system, you're going to have people who are generally able to detect that because they will start to have all of those symptoms that we talked about. >> And let me ask something that I just recently read about that relates kind of to that, I recently read that because warm air doesn't necessarily rise. You can actually have a build up of CO2 right around the face of an astronaut sleeping. And you can actually kind of result get a hypercapnia and you know, people report sleep disturbances, is that true, and as they're kind of more to add? >> Yes, that's absolutely true, so in normal circumstances you're right, hot air is going to rise because it tends to be less dense. And so we kind of have a normal way of creating this circulation, where are expired gasses are going to have some kind of way of drifting themselves off from our faces. So you can still have problems if you sleep inside a sleeping bag even here on Earth. So if you decide to sleep inside a sleeping bag, the odds are very good that you will wake up suddenly and with a start and probably sweating profusely and hyperventilating. Please don't try it, it's actually a very unpleasant experience. I know this kind of sounds like a, let's try this at home and see what it feels like for me, but it's honestly, it's not really something that feels good, I've experienced it, it's not worth it. But in outer space they're not allowed to sleep inside their sleeping bags for that exact reason is the problem can be additionally exacerbated by that. It's also one of the reasons with breathing system design where they're normally on Earth when you're looking at breathing systems. You can put carbon dioxide sensors and you can kind of guess where they're going to go. But a lot of the times in space, they just sort of throw them everywhere. Like they're just everywhere. It's important that everything is covered and that we know what's happening in every region. Because there's not a lot of mixing of the gas that will happen on its own. So you can have little pockets of atmosphere that might be different from each other depending on where you are just kind of terrifying and awesome at the same time. So, Megan said something about in the waves. Yeah, this is my book. So I threw this up here for my zero if you guys ever want a huge dose of science and a lot of talking about the lungs. So it's got a whole chapter in there about hyper cap Niya inside of a famous Civil War submarine. So trying not to plug myself too much because this is nick and Dominic's class and it's really their show. And so I'm just here to talk about my enthusiasm for science and how a lot of these concepts can be bridged into different careers. Like, building spaceships is fantastic. You can do it great that there are tons of other ways that I think breathing and human physiology are relevant to all of our world. >> Yeah, Rachel, I actually just wanted to say thank you very much. But I did want to ask you about the book because I think it's a really cool thing for people to see how your interest in kind of especially submarines is even still relatable to space, right? So with hyperbaric medicine and all of the chamber stuff, I guess the question that I would like to ask you on behalf of the classes. What exactly is your book about? >> So it's about a project I worked on in grad school. So when I was working on my PhD here at Duke, I was specializing in blast trauma, specifically blast trauma from explosions underwater. And I kind of started on this project by accident. My project was not really supposed to be about a Civil War submarine. But it ended up getting lumped into my dissertation overall. But in short, there was a submarine that was built by the confederacy during the Civil War and in 18 64 it used a £200 black powder bombs. So 90 kg is about the size of a beer keg on the end of a long spar to blow up an enemy ship. The Union ships, Uss Housatonic and the submarine, which there's a model behind me. So it obviously doesn't look a ton like normal modern day submarines, but the crew is never heard from again. So they basically all died seated at their battle stations. And it was this really huge mystery. One of the reasons that I started working on that mystery was because of my interest in breathing. And in looking at the balances of oxygen and carbon dioxide, especially in these enclosed environments. And so I kind of thought maybe I could contribute to this mystery because people thought that they had just succeeded inside the close submarine hull. So I was able to show with a little bit of modeling that they really had at least ten minutes before it would have noticed these symptoms of hyper copy that we're talking about. Like these visual disturbances, hyperventilation of like five times your normal breathing rate and none of them trying to get out. None of them unlocked the doors, none of them trying to get outdoors. So, I think someone just said something nice. I'm a big fan of mystery in science too as a scientist. I thought this story was really unusual because a lot of times, if I'm at a party in non covid times. If I'm at a party and I start talking about my work, there will be two types of people. I will immediately find the other nerds in the room. And I mean that as a compliment who really want me to talk more about work and we'll have like, a wonderful conversation. But the majority of people don't really want to hear about the details of my science. And this was one of the only projects where I found that like 100% of the people just wanted to talk about it all the time. So everyone kept asking me questions like you did. They just wanted me to talk about this project and and how it went. And so I ended up writing it as a book because I was looking for a different way to balance out my income. I was doing some scientific projects part time with tooth and I needed a way to balance out my income. And for me it turned into a really good lesson about kind of the importance of being a well rounded person is if you have a story to tell and you don't have the ability to tell it. Then it becomes a lot more complicated. So I wrote it up released it right in a relative pandemic. That seemed like a good plan. But yeah so. >> Then let me ask. So my background is that I'm not an engineer but I work with plenty of engineers in a very engineering capacity. And you are kind of if I may say the opposite where you actually started in the engineering world and you work in a lot of the physiology world and even doing writing that's often engineers joke. Writing don't bring books or don't bring you know writing for me please. How has your engineering background serve you and help you answer and think about medical mysteries. And that's something that's helpful for a lot of people here who are engineers. Yeah, absolutely. So I think especially like you to I would consider you a crossover person as well. I think when you're a crossover person you can become kind of a translator. So for me, having a scientific and an engineering background really enabled me to approach some of these problems from a more mathematical perspective. So previously people have been looking at the physiology and they've been looking at history. And they've been pulling up these historical documents but nobody had actually sat down and calculated the volume of the gas inside the boat. And so that's how I as an engineer was able to create a 3D model in engineering software. Calculated how much this boat would have weighed and therefore figured out where it would have stopped the water. And then been able to solve things like exactly how much oxygen supply will give, how do inside there. How much carbon dioxide would have been producing at a certain work. And so but the other issue is as well, if you're not able to communicate that, then the knowledge kind of dies with you, right? So it's a cross disciplinary area of people like yourself as well who are learning to do both. And learning to do math and science in order to evaluate our real world problems. And then translate them into the human stories that really are the stories of how we live. And how we survive is to me I think the most useful. >> I think it's really interesting how your decision to move from the engineering world. How that worked out and kind of made sense and fit in properly. Because you're bringing the engineering background, but how did you make that decision where you want to end up? >> Okay, yeah, so I see some similar questions in the chat Lois said, what made you transition over more from the physical science to physiology? So I've always been really passionate about physiology just because I myself have a medical history where I call myself a hospital frequent fire. And I'm not going to go into super details about that. But I think that being experienced as a patient has really made me relate to some of the issues in healthcare and in terms of. The way that the human body can fail us even when we're not expecting it to. And so that makes me interested, not just in the physical sciences and engineering, but in how those apply to people. Because fundamentally at the end of the day, I'm a big gearhead. I love cars. I grew up taking apart cars with my dad who taught me when I was young. And I love that stuff because you can see the mechanical into just you can see it and fix it, make it work. But if we cannot do the same thing for the human body and we're breaking down while the car is sanctioned perfectly around us, then at the end of the day, what's the point? So those two experiences combined of previously, already having a love of engineering and then myself having medical issues. We're really making me want to focus my type of engineering onto physiology. And looking at the way that the human body not just survives but fails. So when we're talking about extreme environment, we're talking about healthy people who are now put in a situation where it's very likely that they're going to fail physically. And it's up to us to stop that in advance. So it's up to us to understand it in advance and not to prevent them from dying. That's a really rare opportunity because usually when something like an illness hits, we don't necessarily get a lot of warning. I mean, look how long we've been studying aging, we still can't figure that one out, but like taking a person and depriving them of oxygen. We know exactly what the problem is there, we should have warning for it and we should be able to address that before that becomes a really problematic issue. And so for me, I don't want to say they're the easy problems of engineering because that's absolutely not true. Anything involving humans and human physiology is a complex engineering question regardless. But to me, they're the ones that we should definitely be able to solve. And have the most benefit tasks because they're also we need to move forward in order to build better submarines or to build spaceships that can take us to mars things like that. So, and then Due said, are there any long term side effects from hypoxia decompression sickness etc? Even if you immediately treated. Okay, so I'm going to separate those out. I'm going to separate out hypoxia and then I'm going to separate decompression sickness. So hypoxia is specifically low oxygen or lack of oxygen. If you treat hypoxia immediately, you will have no long term effects as long as you didn't get to a point where you're experiencing neurological death. So if you have hypoxia severe enough that people are starting to have brain cells die off, then it's probable you will have some long term effects that are permanent. However, it does take quite a while to get there and by quite a while I mean a few minutes. So if you have something for example, like with our hypoxia training, we were monitoring the oxygen levels these people were at all times. So we have a pulse oximeter on them, which is like the clip that goes on your fingertip. And those tell you what percentage of your blood is saturated with oxygen at any given time. So because this is the thing that's been done super commonly, we know what's happening with these levels. We know what levels are safe and what levels are unsafe. We're able to monitor those falling levels for people and watch them and give them back their oxygen before they have any risk of serious or permanent damage. So in that case, no, in that case. As long as you have proper supervision and you have the administration of oxygen, then you have absolutely no long term or even short term harm from it. And we definitely we wouldn't even do the training if that was a realistic risk. So that's really important and that's a really great question. Now, one of the things that's been interesting and it's relevant to our current lives is with the COVID pandemic. Some of you might have seen that low oxygen levels and hypoxia are one of the issues that have been happening. So what's happening in those cases is the virus is sparking the build up of fluid in the lungs. And they build up of fluid in the lungs is meaning that the lungs now have less surface area with which they can transmit oxygen into the body and bring carbon dioxide out of the body. And so now you've created a situation where even though you have access to normal area, you have access to normal percentages of oxygen. You have people who are probably going to be dealing with hypoxia and hyper cavapnia just because we've reduced through lung volume, that's functional. And so in that case they can have long term issues. But it's more of a question usually for those patients of the amount of damage that is done to their lungs and restoring lung function in general. Rather than the fact that they were temporarily able to have a lower level of oxygen. Hopefully, that makes sense. >> Sorry, doctor, let's say for better on your phone or aren't able to read the chat we had Dominic asked the classic question of which type of hypoxia would that be? Rose correctly answered hypoxic rates some failure in the actual lungs themselves. So, I just want to reiterate that to get a shot of mental levels. >> Okay, so the decompression sickness is totally different. So what happens is decompression sickness is have you guys discussed that yet? Do you complete PCS? >> Yes. So that was where the videos from this last week and so hopefully no guarantee that everyone here is seeing them. But that was the homework, I guess you could say. >> Okay, great, okay, so I don't have to go into detail about GCS. But just the one second summary is you have a reduction in pressure and the gas comes out of the tissues and it comes out more quickly than the lungs can process it. So before when I talked about how the human body generally responds well, the pressure changes. I should put an asterisk on that because again, the lungs are the most important part of the pressure changes. But they need time to process them so that nitrogen, the lungs can process them fine and the body can handle those pressures change is fine. But the lungs cannot necessarily do it as quickly as we all would like. So with decompression sickness, that's when the lungs aren't able to process the nitrogen quickly enough, those bubbles become lodged in the tissues. That becomes a really big problem because it oxygen real flood. So that is a really complicated clinical problem. It most often happens with scuba divers. That's by far the most common for us here on earth and it really depends on how severe is the case they have and help quickly they're treated. For example, you can have what's called Type II DCS, which means that you have bubbles that are blocking parts of the neurological tissue. So you would have bubbles that are lodged possibly in the spinal cord, possibly on the brain itself. And these people are showing serious neurological symptoms like inability to control a limp would be a very serious symptoms. You can also have milder cases of decompression sickness. So if you have Type I DCS, that's a much less serious situation. So you'll have to light pain. You might have the pink spots on your skin that's like the classic DCS rash. Okay, and in that case you have a much less severe problem because even though it's definitely something that still needs to be treated, your nervous system has not been affected. The reason that matters so much is because the nervous system is one of the parts of the body that has the most difficult time healing. So a lot of the types of nervous tissue cannot regenerate at all. And a lot of them have more difficult time healing than something for example, like a muscle, the muscle we regenerate every time we go to the gym. But neurons in our brain, they don't really do that. So that line between neurological and non neurological has a really big potential impact on whether or not the people are going to have a full recovery long term or not. Now in general decompression sickness, if you notice it right away and you get treated right away, the outcomes are very very good. So your chances go down the longer you're away from a chamber and the longer those bubbles can sit in your bloodstream and just rehavoc and cause all yourselves to die off. But if you manage to get to a tumor really quickly and get re compressed and the long term outcomes are usually pretty excellent and they usually have a really, really good recovery rate. >> And then I had a question with regards to the hypoxia. I think I once read that chronic and frequent exposures to like low grade hypoxia might have some effect on the eyes. I don't know if you've heard of that and can agree or disagree. >> I'm not familiar with low grade hypoxia affecting the eyes, but low grade hyper arcoxia definitely does. So that's low grade elevated levels of oxygen and that's actually one of the most frequent problems that we have for patients at the hyperbaric chamber. When they come in, these are people who are usually coming to the chamber for medical treatments for some kind of illness. So a lot of times they'll have a lung issue that's interfering with their ability to process oxygen or they may have an infection where they need additional oxygen to help their body that circulation to that tissue to help it heal naturally. And one of the most common problems is that the elevated levels of oxygen will cause changes to their eye and they will have blurred vision. Now this is very interesting. We can look back to that. The good news is it's temporary. So it's very temporary. It's annoying, but it's not medically serious. It goes back on its own once they stop having the treatments. And so it's not really something that we worry about except for trying to find ways to kind of attenuate the inconvenience to them during their treatment period. But the reason that the eye is so sensitive to changes in oxygen level is that the retina is actually one of the parts of the body that hypoxia uses more oxygen than anything else. So like the heart gets a lot of credit because the heart is really oxygen hungry because it's always beating away constant muscle use. But the retina in the back of the eye uses a spectacular amount of oxygen. And what that means is that visual changes in visual disturbances are actually one of the best ways to detect hypoxia and the one of the first symptom. So if you have hypoxia, you start to get tunnel vision and that's actually the peripheral areas of your retina ceasing to function because they're not getting enough oxygen. You also start to lose color vision. So a lot of times for hypoxia training will hold up a card with like the color wheel on it and then as you put your oxygen back on, you watch the color wheel go from black and white back to color. And so you will actually have like a dog, black and white vision if you have insufficient oxygen. Now whether or not you notice that is really dependent on whether you've been properly trained to notice that, but it is one of, I think the cooler parts of that type of physiology. >> Fantastic. And then a really good question in the chat from Lucas asked if an astronaut is experiencing DCS like from a suit failure, would it make a difference if you treat them with repressurizing up to one atmosphere or re pressurizing them with a greater than one atmosphere to avoid any issues? >> Okay, so there are a couple of things happening here. So astronauts, the space station in general is not pressurized. Yes, it is, it is. So when they go out in their suits, they're already slightly depressurized. The space station is one atmosphere of air and that's for safety reasons. But their suits are usually 100% oxygen at a reduced pressure. So, if they're experiencing DCS, it's because they came from one atmosphere to reduce pressure too quickly, which Lucas is kind of nailed. So in terms of DCS treatment, there's kind of a standardized protocol for that. There's a standardized set of tables called the Navy tables. And so I think in a real hospital, if this person were like actually coming to a hospital somehow and being treated, then they would probably just put them on a standard Navy table, regardless which is an increase of above one atmosphere. But if this happened in the space shuttle, one atmosphere is probably the limit of what they have available to them. So it's most likely that they would put them on one atmosphere and then give them pure oxygen. So, an increase in the pressure is usually going to be clinically beneficial for treating decompression sickness, but in that case they would be limited by the resources that they have available. And it's usually not as helpful to pressurize someone past where they started if that makes sense. So they started at one atmosphere and then they got DCS from reducing that, usually don't get a ton of additional benefit from pressurizing over one atmosphere. So if we have that ability were in the hospital to have a great chamber, sure, go for it. If you're in outer space, you're probably still going to get a ton of benefit from the one atmosphere. And then the most key thing with DCS and with the DCS treatment is always a beauty breathing oxygen. So when you are experiencing DCS, obviously that's that's a that's a surfeit of nitrogen in your blood, right? You have too much nitrogen. What you want to do is make sure you're not exacerbating that you want to make sure you're not introducing more nice rivers in the breathing gas. And so they put them on 100% pure oxygen, and that helps increase the gradient so that more nitrogen will diffuse out more quickly. So, in that case that he described putting people on nitrogen is around oxygen is going to be more important than pressurizing people beyond their original pressurization limit. >> And then a really good follow up from Sofia here is what would be the time frame from getting someone to a hyperbaric chamber before we start to worry about the long term effects of DCS. And I think part of that answer is going to be also, where are they coming from? Is that scuba on a space station? So maybe you can talk about your thinking there. >> Yes. The time rate for DCS and long term attacks is really going to depend on the severity of the case. If you have a type two DCs where you have a neurological symptoms, those will usually actually, there's so much variability. I'm hesitant to give one answer and say this is always the case. So just know in advance, I'm giving you kind of all part, there is a lot of person to person variability and exactly what happened to them and their. Their own physiology, but in general it urgent's you get someone to a chamber within 24 hours of the injury. The problem with DCS is that it's not always immediately obvious, if somebody has an extremely severe case, they might surface and then have symptoms within 15 or 20 minutes after surfacing. But typically, they won't have symptoms for between one and 24 hours after surfacing. So people can come home from a dive and feel completely fine, and then wake up the next day completely unable to feel the right arm. That's an actual case of a friend of mine, [LAUGH] got DCS that way, he call me at 7:00 in the morning. And so in that case, obviously I just picked him up and took him directly to the local chamber. I was not at Dundee at the time, this was in Florida, but that's what I mean by tons and tons of variability. But if someone can get to a chamber within 24 hours of surfacing, then that really really improves their chances of minimizing any long term side effects, long term effects. Anything longer than like a week or so and the damage is probably already been done. We typically don't even necessarily treat people if they're out more than a week or two from their original injury. Because at that point, they're not dealing with bubbles anymore. They're dealing with tissue damage and hyperbaric is not necessarily going to help with the tissue. Okay, just curious why would there be no long term effects on the eyes if there is hypoxia? Do the cells in the eyes not immediately die when they don't get oxygen? I actually don't know, I don't know whether there is not a long term effect. I think that this is just one of those things where some cells are more robust than others, and those just aren't the ones that happen to go in advance. So, it's entirely probable that at some point, they do start to die. But at that point, if we're seeing cell death and we're probably seeing cell death in other areas as well. And at that point, you have a more systemic issue than just the eyes. >> Yeah, to add to that, if you could magically snap your fingers and remove all the oxygen, cell death would occur. But I think the question when we phrased it was low grade catachronic exposure to hypoxia. Well, as long as it doesn't drop too low for too long and cause brain death or something else. The eyes have the added benefit that so much blood is being directed to the brain at all times that the eyes are getting so much of that blood. So that if the brain shuts off, well, the eyes will shut off, kind of thing. >> Yeah, they get kind of the benefit of proximity, right? So, I don't know if anyone has ever had like even a minor head laceration. So, even if you get like a very minor cut on your head, it just bleeds like crazy, right? So, this is a thing that happens a lot with little kids and it can lead to a lot of anxiousness and panic with the people who are on looking. Until you can tell exactly what has happened and just exactly how bad the cut is. But even a teeny tiny cut on the head is going to bleed just an unreasonable amount and it's because of the amount of circulation going out there. So the blood supply to anything making above is so intense and that includes the eyes. But they're all really tied together and they're all really benefiting from the activity of the brain, so. Okay, hold on, this is a long one, so I'm going to read this from Lucas. There's an interesting video of a NASA suit test in the 60s where a test subject suit misses pressure. And he passes out within I think 15-20 seconds, they immediately pressurized the chambers and he started being okay. So was wondering what the effects on the lungs would be from being suddenly exposed to a vacuum. Okay, that moment I expose you to vacuum, then the lungs cannot come back from, all right. So there are two possibilities here, the first possibility, rapid depressurization while the person has their larynx open. Okay, so this is the best case scenario, best case scenario, someone is talking or just exhaling or even inhaling. But there is no closure between the lungs and outside world. So when that happens and you have the vacuum loss, the lungs itself can actually handle that fine. So as long as the gas has a place to go, the lungs are going to be okay. For a lung to fully collapse, you actually need gas space to enter from the outside of the lung. So it needs to be inside the body but outside the lung and that's really what will make the lung collapse. If you have a sudden reduction in external pressure, your lungs are not really going to collapse. Unless you have some kind of preexisting physiology, which is the thing that can happen but would have probably been tested for in advance. So there are some people who have like natural system pockets in their lungs. That's a totally different scenario, but in general it's not going to fully collapse from a loss of pressure. Because, [SOUND] sorry, so somebody is driving by, so my dogs are about to get excited [LAUGH]. So the lungs in that case will be generally okay, a full and complete vacuum, I don't know about that situation. But as long as the gas has a place to go out, they're generally fine, and you're more worried about the lack of oxygen at that point. Now, the second situation is if someone is holding their breath, this is one of the big problems that happens with scuba diving. So I don't know if there are any other certified scuba divers in this class. But the number one rule with scuba is you just never hold your breath. Like no matter what else happens, if you are freaking out, if a shark just bit your leg off, you go to the surface. Screaming the whole way up because you cannot hold your breath on your way up. So in that case, what happens is you have a reduction in the pressure where you have a gas fully trapped in the lugs. That is your worst case scenario because the gas is going to expand and it is going to go somewhere. What happens then is what we call an arterial gas embolism, the lungs will rupture and they will send that expanding gas out into your body. Now, where in your body will it go? That depends, it depends on the person, it'll change person to person. There is a variety of ways that expanding gas, not travelling gas level can cause mayhap. But basically you have now just injected a huge chunk of gas in your body and it's going to block all of the blood. So, there have been cases where it's gone directly to the brain. There have been cases where its gone directly to the heart, and it is an extreme medical emergency. People tend to lose consciousness almost immediately and so it should be very obvious when that has happened. And that requires immediate repressurization to shrink that gas bubble down. So that is really bad because you can actually rupture your lungs if you ascend from a difference of three feet of water. So if you start from three feet beneath the watew with a lung full of pressurized air and then you go to the surface. That's how fragile the lungs are, and that's how easily they will rupture. So that's kind of the one, the lungs can still come back from that, the lungs actually are remarkable in that they self seal. So once they rupture. They just patched themselves back together, it's totally fine. You don't need to do anything else to them, you need to get rid of the gas bow that's now floating around your body causing mayhem. But the lungs themselves are going to be okay. >> So for those of you that are very interested in buried trauma or especially trauma in the lungs, I would recommend going and looking into the different, the different pleura. The different pleura and the visceral pleura and how those work and kind of understanding that model with the two different almost balloons. I think is what Dominic and I explained them as before. I mean how those interact to show what can occur if you puncture a lung or have some other form of buried trauma. >> Absolutely. Actually, there's a pretty cool animal fun factor. So you guys have already talked about the flora, which is basically like a water balloon, once they're shoved inside it, so that helps lubricate their motion. Some people theorize that those flora are also why we can't handle big pressure differentials. What I mean by that is, so snorkels need to be a fixed depth, you cannot take a garden hose and go to the bottom of the pool. And use the garden post as a snorkel, because you are now at a higher pressure than the area trying to breathe at one atmosphere, you are at like 10 ft and one atmosphere. So your lungs are not strong enough to inhale against that much pressure differential, you only get like a couple inches beneath the surface of the water. The one major exception to that is actually elephants. So if you look at elephants, they can walk through the water and they just have their trunks sticking out. They are one of the only animals that does not have a pleura around their lungs. And people have theorized that they evolved to lose the pleura so that they could do precisely that trick of walking around under water to stay cool with their trunks so far above them. And still managed to inhale against that pressure differential. >> But that's awesome, actually that's so cool, I never read that. >> Yeah, and it also ruins a lot of movies. There's so many movies where people are like hiding at the bottom of the river like a reed or something like that. Now, now you're going to ruin it for everybody because you won't be able to not tell the caliphate. >> But that also explains I've always wondered why old timey diver's and those big steel cage suits had to pressurize their air hoses. That makes a lot more, >> Yes, that's why for our lungs and our breathing processes are actually surprisingly weak. We're very good at acts hailing, we have a lot of muscle strength to do that. But when we inhale it's actually under normal circumstances, that's actually a relaxation process. So, exactly yeah, your body kind of just relaxes into its normal state and the lungs still on their own because they created a vacuum. So when we have to forcibly inhale, that requires muscles that we don't use very frequently and that can be very taxing. We actually have a project coming up in the chamber that I think it's going to be really exciting. We are looking for better ways to strength train divers to breathe, which films almost silly when you put it that way. But we are working on ways to introduce small amounts of carbon dioxide while they're exercising. To see if we can strengthen the muscles that they use for inhaling in order to make them more efficient underwater during activities. I'm pretty excited about that, wanted to go be a good project. >> [INAUDIBLE] The classic thing that we talked about in the course especially when working with high schoolers is the science fair. If you guys have seen the science fair model of the lungs where you take two balloons and you put another balloon at the bottom. And you kind of cut a water bottle like that, you can pull the bottom balloon and then the top balloons will inflate and I'll send a link for that. But that's getting at this whole process of how the lungs kind of r shaped up pull pressure into them and that's kind of why we're weak breathers in a way. >> Mhm. Were surprisingly bad at the process that we need to do constantly to survive. >> It's been an incredible guest speaker today. Thank you so much, once again- >> Thank you for having me.
