We're going to move on to our next lecture. Dr. Lance Davis is certified in family medicine and undersea and hyperbaric medicine. And he is skilled in primary care, emergency and urgent care, hospice care, and wound care and hyperbaric medicine. And he said that he is a U.S. Navy diving medical officer and flight surgeon. And he says he has a slide that will help introduce him, so we will keep it short. And welcome to day three. All right, good morning, again. So I probably have the most chaotic and atypical talk of the week that's been the nature of my career. I'll jump forward a bit. Dr. Mary Hanley, your current president, asked me to do this talk because we have a little overlap in our careers. And the guidance was pretty open. And she said, make it fun. And there's going to be some people of all different walks of life and some military and former military throw some pictures and videos in there to make all that a thing. So here we go. So here's my tie-in. So I am a Navy reservist, have been since 1999. I am board-certified in family medicine, undersea and hyperbaric medicine. I'm a wound doc. On the reserve side, I was a diving medical officer. I was with the EOD teams, I was with Marines, various things. I'll go through that. I'm currently a Navy flight surgeon, do some dive medical officer stuff for the South Carolina Aquarium in Charleston, where I used to live. And just to make myself comfortable in a room of occupational docs, because I'm actually not one, but I do occupational medicine a good bit, I also have that DOT, commercial driver cert, and I've done thousands of clearance exams for first responders, police, firefighters, EMTs through North Greenville Fitness in South Carolina. So I think I speak the language, but I couldn't write you a board certification question. So sorry. Our previous speaker did a great job with that. Okay, if you guys can look at these questions, because I always talk to where my audience is at, and I don't really know. If you're home and looking at this on Zoom, if you could kind of just throw in a brief answer if you're any of these things, and Jeff's going to give a toll for me, and by the end of the talk, maybe I can tailor to you a little bit as I try to bring all this together. Okay, so learning objectives, I think they're published at home, but we're going to learn a little bit about the physiological events in Navy fighter aircraft. We're going to distinguish some key overlaps between the undersea world and the aviation world. We're going to identify some key roles for communication between military and civilian medical entities, especially with regards to occupational and operational medicine. I have no financial biases. I have no off-label therapeutics that we're going to discuss. However, I will warn you, there may be some Bundy effect, some Bundy bias, and some Bundy phenomenon. If you think way back when you're in college, you might have heard of those. So the Bundy effect is the tendency to develop a fixed belief that one's glory days in an academic, athletic, medical, or military organization was and always shall be the golden era of that organization. The Bundy bias, of course, is to believe that one's own role in an organization or system associated with the Bundy effect was and forever will be remembered as the greatest of all time. And the Bundy phenomenon, the fixed belief that other people really want to hear detailed historical nuances pertaining to the Bundy effect or the Bundy bias. So I'll own that ahead of time and be forgiven. Thank you. All right. So one question I'm putting this together with this audience is, is operational medicine the same as occupational medicine? So there's overlap. And I kind of say operational med is mostly med on site, equivalent to a primary care house call in a lot of ways. Not always, but for me, it's a general rule. In the hyperbaric or undersea world, Navy side, partially yes, due to clearance exams and treating occupational exposure, namely decompression sickness with return to work in mind, but it's not all that, so it's partial. Occupational medicine and flight surgery I've learned is extremely occupational, almost exclusively occupational medicine with some primary care thrown in, but occupational docs are primary care docs for whatever catchment that you have. So yes, in general. So I still feel comfortable in this milieu. Why do operational military, especially Navy docs go through operational training to get to operational medicine positions? Anybody in this room want to comment on that? I know I've already heard I've got some military folks, military background. What's your answer to this question? Okay, relevance to the command, all right. Anything else? So for me, it's twofold. To be excellent at operational and occupational medicine, I'd offer one gains advantage with an excellent understanding of the operation and the operators, okay? And Dr. Patel hit on that too, so going to the worksite, going to the factory, which you guys have already done, getting in the rig with your truck drivers, getting in the rig with your firefighters, getting in the airplane with your aviators, getting under the water with your divers, the medicine, the physiology, the outcomes, all that rolls in and I still believe the best form of primary care is the house call because you can talk to your blue in the face about diabetes and you look in their cabinet and there's your answer if you're doing the house call. So it rolls. And then again, for CDL examinations, which I've done a bunch, I try to get, I've been in fire trucks many times, so when I'm saying, show me your range of motion, I make them do range of motion with wide-based arms rather than narrow because they're turning a bigger steering wheel than in a car, okay. How did I get here today? So I took the most general field of medicine and I expanded it, so family medicine, blown up into all these other things I've done. Chapel Hill for BS in biology, nutrition, MPH, MD, family medicine residency in Charleston back in 97 to 2000, I took my Navy commission in 99, 2000-2005 I was with the Marines as a shock trauma asset, that's the green side because the Navy supplies the doctor to the Marines. In 2002, and this ties in, I just found my way as an early reserve lieutenant that didn't know what I couldn't do, thank goodness, I ended up in Panama City for the nine-week diving medical officer course, which was hands down the best experience of my professional life. I wish I could do it every day. We'll get a little more to that, 2003 mobilized in Kuwaiti Desert with the Marines and then southeastern Iraq with the 323 and the original shock trauma platform, here's a Bundy effect, so we were the early ones, we were the first in the doctrine, we were the ones doing mobile tent ER up and down in an hour, treating patients, possibly married to a forward resuscitative surgical suite. Okay, all right, I did some ER along the way, in 2004 I took over a failing unit, hyperbaric unit at Roper Hospital in Charleston, built into three chambers plus a wound clinic, it was level one critical care, the full emergent pathway for decompression sickness, arterial gas embolism, necrotizing fasciitis, I was on call non-stop for 13 years, occasionally away from there on the phone for one of my staff docs, but always on call, and then eventually your president, Mary Hanley, took over after I left, she took over in 2018, I'm still actually on staff, although I haven't worked there in a long time because I live up in Asheville, okay, talking fast, all right, 2005 to 2008, here's my golden years, the best time in the system, EOD in Charleston had reserve and active duty units, I got to be their reserve DMO and the active duty hyperbaric guy in Charleston, so I was like the reserve pilot, so it was both, they overlapped, for three years of my career, that was the golden age, Bundy effect in full force, I was inactive for a few years because I was on call at Roper and my units moved to Virginia, I couldn't go and I got shaved off, so I got back into my reserve life in 2013, I was with Expeditionary Medical Force, that's a tent hospital, okay, 2017, that's when I went to flight surgery school as a 49-year-old commander with the 22-year-old pilots out of the Naval Academy and the 28-year-old hot shot docs out of residency, or out of internship, and then I'm creaking my bones joints, but got through it, so then I'm a flight surgeon, 2018, ready to do it, they messed up, I didn't get a billet for a year and a half, so I forgot everything, I barely knew and never got any OJT, boom, September 2020 to now, I've been doing civilian hyperbaric and wound stuff up in Asheville at a level two, no longer emergent, but finally in December of 2019, I got a billet, I'm a flight surgeon with F-18 Growler Squadron, VAQ-209, learning the whole deal, everything about how to actually do the job, COVID hits and we deploy to Japan and we're the first to internally mobilize ourselves medically, so that was a big challenge, got it done, and now I'm with VFA-204 out of New Orleans, they're an F-18 adversary squadron, that means they're the practice top gun guys, all seasoned, you know, older pilots with their aches and pains, but they know they're great, they're amazing, and with all that, still not even knowing how to do my job very well, I think, but somehow or another I got hit as a 2021 Navy and Marine Corps Reserve Flight Surgeon of the Year, so who knows, and hopefully I'll be a captain soon. All right, that's, Dr. Hanley asked me to do this talk earlier this year, I said, what about, I'm not an oc doc, she says, well just, it's an eclectic audience, do something interesting from your unique perspective, make it fun with some military cool stuff, okay, copy, very busy spring, I had three broken ribs and post-vax COVID, so that was miserable and I was way behind on everything, so I finished my slides this morning, all right, forced me to look, however, this topic made me look deeper into what I thought I knew already and had glanced over, and this is going to make me a better doctor, so thank you for indulging me, I don't know if it's going to help you in your careers at all, but I hope you get something from it, so I've tried to make a few points, pearls that you can take away while trying to entertain you, all right, so the overlap between aviation medicine and hyperbaric undersea medicine, it's decreased at this point, Bundy, Bundy, Bundy, because the decreasing emphasis on decompression sickness and hyperbaric treatment for physiological episodes in the F-18 and the T-45, let's take a deep dive, all right, so a physiological event is defined as symptoms of a physiological episode and some sort of aircraft malfunction, loosely termed, but the aircraft is contributing, and a physiologic episode is just symptoms in flight with no discernible malfunction, but as we'll learn, those lines are pretty blurry, so we call it PE across the board, the Air Force had this problem with the F-22s and they had a process for investigating, the Navy borrowed and improved on some of that afterwards, but it was kind of tandem, you see pictures of the two aircraft there, all right, here we go with gratuitous visual imagery, which is a military acronym that I coined last week for this, so let's go here. And this is just for fun. What is this? Everyone here is the best there is. Who the hell are they going to get to teach us? Captain Pete Maverick Midgeholm. Let me be perfectly blunt. You are not my first choice. You were here at the request of Admiral Kazansky, aka Iceman. You were left to offer the Navy what that is I can't imagine. With all due respect, sir, I'm not a teacher. I just want to manage the expectations. What the hell? Good morning, aviators. This is your captain speaking. Then we're off. Here we go. Three... Two... One. We're going into combat on a level no living pilot's ever seen. Not even him. You think up there you're dead. Believe me. My dad believed in you. I'm not going to make the same mistake. Someone's not coming back from this. Those are your pilots. Anything happens to them. Smoke in the air! Smoke in the air! You'll never forgive yourself. No turning back now. Come on! Oh, jeez! Having any fun yet? There's a lot of excitement, obviously, in the community about that. And since most of the current aviators grew up and went into it for that reason, obviously they're somewhat skeptical, but deep down they're like excited boys and girls. Here's my tie-in, and this goes right into as I was trying to build this presentation. I finally got to fly an F-18. That color vision problem just got me grounded. Believe me. My mask was on when we took it. Seriously, you learn so much in five minutes. Watch how fast the altimeter goes. Wow. Fire in the holes. 23,000 feet. Key West. Key West. And we're going to go outside while dropping microphones. Oh, jeez. Yeah, I didn't plan to do that. Right now, we're just light-hanging in my backpack, which stayed all night. Cutting profusely. That's another thing to note. You know what? I think so. The great thing is my A2 has just arrived for vacation and just made it to Niagara, and that's how they got to see me coming out of the plane, and of course my pilot looks just like Goose. Anyway, okay, so there's a little indulgence there, but the point being is that the point being is that just finally flying, and I should have flown with them much before, but there were multiple reasons, including the dreaded occupational thing. My color vision had slipped just below standards, and getting a waiver as a non-critical air crew was the longest process ever. So I finally flew legitimately, but just a few weeks ago and in preparation for this talk, so it all really ties together. So in flight medicine, the delta between doctor and doer is dramatic. In other words, way back in the old days, flight surgeons actually could come out as small craft pilots. That's gone. We could roll it into hours if we wanted to go for our own certification, but the delta is very dramatic. But being in the cockpit, I actually did move the stick and made the airplane go left and right, so technically I flew an F-18, but I ain't no F-18 pilot, that's for sure. All right, some content-oriented videos, and we're on track, so I'm going to let the Navy Safety Command do a little talking, and again, try to get everything synced up. Two videos, short videos about what the Navy did to address the issue of the physiological episodes. All right, I'll let them explain it, and then I'm going to do a deeper dive, and we'll tease out some physiology. All right, so Jeff, if I get this right, I've started that. I'm Commander Adrian Jobe, call sign CAPTCHA, leading the Navy's physiological episodes action team. In 2010, Naval Aviation saw a rapid rise in PEs. A comprehensive review was initiated by PACFLEET, and in 2017, the PETE was established as the overall lead for the investigation. After three years of analysis and aeromedical research, we've added new language to Chapter 8 of the CNAP 3710 manual. You can download the document from the Airworthiness website. Here are some key takeaways. 3710 now outlines what actually causes PE's and what can be done to minimize risk to aircrew. You'll also find a chart that shows common physiological symptoms and various factors that cause them. Additionally, we introduced the concepts of strategic air brakes and the aircrew controlled breathing cycle, or ACBC, providing guidance to aviators when they can safely remove their mask in flight and reset their breathing. Throughout our journey, we've learned a lot about PE's and now fully understand the complex relationship between humans and high performance aircraft. PE's remain Naval Aviation's number one safety priority. Educate yourself on the new information. Download the 3710 today. So in my audience, if there are folks who are either level one hyperbaricists or FAA examiners, this is where this might touch you. If an aviator maybe a reserve aviator presents to you and maybe didn't tell the military flight surgeon everything, but now is worried because five days later they're still feeling wonky after a flight. That's kind of where I'm going with all this. And this one, let's see to get that started. That's not on YouTube, but it should. It still comes up. It's open source. A PE is a physiological event. And that's when the aircraft has some sort of malfunction, usually in the pressurization or breathing systems that produces symptoms in the aviator. We saw a huge rash of PE events and really our T-45 and F-18 aircraft. And they started to increase at a pretty rapid rate. And it was decided that, hey, we need to really get after this and figure out what's going wrong. The Navy stood up the physiological event action team. And we've been for years now getting after that problem, mitigating, and now even preventing physiological events from happening. The PE was established basically to really get the conversation going amongst the important people to get after the effort. So DOD, industry, academia, aerospace medicine. And out of that, we had the RCCA, the root cause corrective action teams. And each of them did their own independent studies to try to uncover the mystery and looking at the aircraft, but also looking at the human. Because again, PEs don't happen to the aircraft. They happen to the human being. But for folks having symptoms in the aircraft, there wasn't something we could point to immediately. Instead, if I just fix this, all the problems should go away. And so kind of the thinking of the RCCA team is that this is definitely multifactorial. It's different every day, different every flight, and different for every pilot. And that's the way that we had to approach it. So physiological event, you have to have symptoms, but you also have a failure in the aircraft. With a physiological episode is you have symptoms, but you can't attribute it to anything in the airplane. We looked at patient data for about three years, and we divided the patients into the type of aircraft malfunction that occurred. Was it breathing gas systems or was it pressurization systems? And then we kind of started to figure out, we need to start educating the aviator on, hey, how the system works, how is there to protect them, what it can and can't do, dispel any myths that are out there. The flight environment is an overall physiologic negative environment. So you have to be in optimum physical shape to endure the flight environment from a breathing standpoint, from a cardiac standpoint, from a cognitive standpoint. So you have to compensate for the negatives in the flight environment, and you have to be a top athlete. The actions that the aviators can take to make it safer for them to get in the aircraft really kind of come down to a couple of things. So making sure that you're not dehydrated, making sure that you're eating well, that you're in good physical shape, because, again, it's a hostile environment. Two is not normalizing deviance. So if there's something on the aircraft that isn't working right, just don't take it and go fly. We've done a lot of stuff to the aircraft. We've learned a lot. We're doing predictive maintenance now, and we're doing these things all at the same time. All at the prevention of PEs from occurring, and then with the breathing gas side of the house, a lot of it's education. A high-performance, high-altitude flight is not something we necessarily do every day, and it's very different than just us walking around or sitting at a desk. So the value of that PE roadshow is being able to explain what those differences are, what the gotchas are, and ultimately restore confidence back to the airframe so that they can go out and deliver capability and not worry about the system taking care of them. Eventually, the whole fleet will be speaking the same language and have a new understanding of how the systems work, what are being done in the systems to mitigate the PE risk, but also how do I, as an aviator, interact with those systems in the aerospace environment, and how can I protect myself from a PE or a physiological episode? There are a lot of corrective actions that are still out there that need to be worked. So we can declare victory in the sense that we know what the problems are. Now it's time to do the hard work to go fix those problems. Still Navy aviation is number one safety priority. This is a risky endeavor that we do, but as close as we possibly can, it is our goal. We saw that next train, by the way, as it landed. Okay, so there's a lot just even seeing it. You can start as doctors, you start to break down and analyze, which is what a lot of the job is. The next thing on the slide, if you're following along, is a third one. This is the third video. If you have interest in this, if it's all professionally relevant to you, this is the hour and a half long actual road show from which I bring a lot of the deep dive from. I had to watch it three times myself recently just to process it all, but if you're interested, it's there for you. I'm not going to play it, obviously. So now we just go back to the slideshow. Okay, we won't have videos for a while. You can relax. All right, now, so I call this a story of success and humility. I call it a story of success because the outcomes you'll see and the changes that have occurred, I call it a story of humility because a lot of players in this had to, both engineering, pilot, operators, and doctors of various types, had to say, maybe my initial assumptions weren't right, including this Al Bundy, because in 2017, I was going to flight school. I was the reserve, first reserve guy going to flight school, and I was selected down this pipeline because of my hyperbaric background. 2017, we had all the carriers loaded with chambers. We had dive teams on board and undersea medical officers to treat what we thought was DCS and aviators, but we've had to look at the evidence and adjust accordingly, and that's a source of pride for me because of what we do in medicine and science is we have accountability, and we have to change with the evidence, right? Obviously, something we've had to deal with in society. So this is a story of success and humility to me. The problem was, as said, increasing reports from 2010 to 2017 of PEs creating much anxiety. Pilots were talking about this all the time. Now, was there a social media herd panic effect? Obviously, yes. A lot of it in the older days, pilots would talk about this stuff, but it wasn't propagating. They just called it, I had stress during flight or different things. By 2010, there was a culmination of this, but it did drive action, and the phenomenon was real. Was it sometimes dramatized? Perhaps, but there was a real core to it. The T-45 program, which is a trainer aircraft a lot of times, shut down, and the F-18 continued to operate, but with a lot of anxiety from pilots and a lot of downtime from the operation. The heyday of the investigation was 2017 to 2020, as we said, and Naval Aviation and Boeing were working independently, and then that PE action team was a great concept, a flag level type of thing, and then they actually brought the flight surgeons in, which wasn't originally happening for some reason, but the commander you saw did a great job of pulling it together. All right, let's talk about the signs and symptoms. Lightheadedness, headache, concentration problems, irritability, sometimes cyanosis of the fingers, visual and auditory disturbance, pins and needles, tingling. Oh my gosh, what could that be? I got the flu, I got COVID, I got decompression sickness, I got hangover, I didn't sleep well. I mean, so many of these things are so nondescript, but they were happening in flight, and sometimes they were lasting 72 hours or less, with or without specific treatment, and sometimes they were lasting more than 72 hours, very persistent. People were thinking, including this dual-hatted individual, that hypoxia, oh, was that doing it? And we classify in aviation different forms of hypoxia. Hypoxic, just not enough oxygen, so hypoxic hypoxia. Histotoxic, like cyanide, right, not letting enough oxygen get on the hemoglobin molecule. CO. Hypobaric, you have, you know, you have just decreased partial pressure, you're not pressurizing the cabin appropriately, so you're just not driving enough oxygen into solution. These are all things people thought about. Decompression sickness, with or without arterial gas embolism, was, it just seems like it had to be that, right, where you're flying high, you got weird symptoms, you know, the test of cure and everything, decompression sicknesses, did you get better in the chamber? Sometimes they were, but was that self-resolving at 72 hours for reasons? Maybe, maybe not, but there were persistent symptoms despite chamber treatment. Again, contaminant, were we breathing hydrocarbons, because all those symptoms, if you go sniff gas at the gas station for long enough, you're going to feel all that stuff, right? Nutrition, hypoglycemia, where guys, you know, skipping lunch and doing their second flight of the day, they hadn't eaten, of course. Dehydration, dehydration, let me say again, there might, you might see dehydration on a question at some point. Fatigue, sleep deprivation, stress, hyper or hypocapnia, right, all the classic physiology, all the things, all reasonable hypotheses, and may have been contributing. So the solution was comprehensive investigation. We've seen three years, 2017, 2020, 8,000 plus pages of technical documentation, 5,000 hours of meetings at all levels, $50 million of investigation. One thing I've learned in the flight community, I didn't learn in the Marines, I didn't learn in the divers, I didn't learn in the hospital, is they burn $40,000 an hour to go on a trip. They don't care about human resource costs. I can get orders to do anything I want, whereas they'd be squeaked out in the other form. So this kind of money, it seems huge, but in aviation, there's a lot of money being spent. All right, as said in the video, no single smoking gun, complex, multifactorial, stacking of many small issues, key intuitive point, combination of aircraft, environment, and aeromedical. We'll get back to that. Now, finally, 466 recommendations in publication for aviator performance, maintenance issues, adjustments to the system. No overarching mechanical design flaw. Everything worked as it was supposed to in most cases, but things could be tweaked and better maintained. Specifically, the environmental control system can be tuned to have a smoother cabin pressurization cycle, and that'll go to etiology here in a bit. Ultimately, the $500 million of fixes budgeted to make these tweaks on the airplane side. The benefit, though, is other airplanes besides this platform will get the benefit of that as newer editions come out. We're learning how to be high-performance, high-altitude operators in the safest way possible. Predictive and targeted maintenance, in addition to reactive or planned maintenance, there's a HART program I won't get into, but the SLAM stick is basically a memory stick that goes in the computer in the airplane that records all kinds of minor fluctuations that they weren't recording before, and that's given to maintenance, and then maintenance does more predictive earlier maintenance on certain systems, exactly what you'd want before launching, but really with a focus on it. This is human and machine. NATOPS, that's the Naval Aviation Bible, is NATOPS, you saw a picture of that, modifications. Once it goes in there, everybody's accountable for that. That is law. The word shall is used in NATOPS. That means without question, every CO is responsible for that, every safety officer, every pilot, and don't normalize mechanical deviance. What that means is a little wobble here, my mask felt sticky, I didn't breathe smoothly, my seat didn't feel right, my uniform, my straps, whatever it is, don't accept deviance. That needs to be shared with the maintenance shop as soon as you land, and they need to get on that so that you're not getting bigger and bigger variance. Mechanical variance, one circle on a Venn diagram, there's a picture of NATOPS, again, the Bible of Naval Aviation, I know the Air Force has something similar. What it's not, it's not hypoxic hypoxia, it's not hypobaric hypoxia, it's not histotoxic hypoxia, it's not anemic hypoxia, it's not contaminant. If you're breathing OBOGS, which is the oxygen supply system in the cockpit, you're basically breathing hospital-grade oxygen. They found that it does a better job of producing high-quality clean gas than they expected, than it was even designed for. They're producing oxygen in the same way that a hospital is, and there's no entryway for contaminants, so that was actually a pleasant surprise. I watched all the references and all the places they tested. These guys really did their homework. They were working in a variety, including Naval Experimental Dive Unit, so that's my briar patch, throw me in there, I'd be very happy. And what it's not, most of the time, almost all the time, enough of the time to put it way in the corner, is decompression sickness or arterial gas embolism, so Al Bundy has to sit in the corner. Here's some good results. No significantly harmful physiologic events since May of 2019, because we're preventing and mitigating. Etiologies are now leaning towards two mechanisms of injury. The short, acute, is a combination of respiratory and metabolic alkalosis, right? So I can induce in you symptoms of alkalosis faster than hypoxia, because you can hold your breath for two, three minutes, and you won't like it, but you'll be okay. I can make you tingle if I make you hyperventilate for 15, 20 seconds, right? So the respiratory alkalosis is quick, but if you do multiple flights and you're not hydrated and you're doing a lot of increased work of breathing and your gear is tight, so you're guppy breathing and hyperventilating, all these factors go in, you deplete your bicarbonate renal reserve, then you're in a metabolic alkalosis, and it takes you two to three days, aka 72 hours or less, to recover, okay? So there's phase one. So this was our big finding, and again, it's not hypoxia or DCS most of the time. Now there is some cautions here I'll give you at the end when I switch hats to the dive side. Some of the main physiologic event symptoms are thought to be due to concussive effects. In other words, when we're pressurizing that cabin and you're going up and down and up and down in the atmosphere, boom, boom, boom, boom, boom, you're actually getting a series of small concussive events. So the analogy is if I hit you in the head with a baseball bat, you're going to have a concussion. If I ting your cranium with a baseball bat or a ball peen hammer over and over again, you can get a concussion. What was also found is a lot of aviators, hey, guess what, occupational docs, sometimes people aren't always honest with their history. Yes, this doctor is surprised. These doctors are surprised, right? So what you found when you took a lot of the aviators who had the long symptoms and you went back and you gave them safe form, no harm, no foul, did their history again, they never reported, even when they were trying to get into the military at 18 years old, they never reported they had three concussions in high school football. And guess what correlates, okay? And guess what correlates when you start scanning the brains? You start seeing white matter, white findings, so you're starting to see some scarring. So this is really important. And so those that persist over 72 hours, and in the handouts I've given you that are online is actually the Navy's clinical pathway flow sheet, and all this is captured in there. So it's propagated now to the different players, and you can look at it, and if you ever are interested, you can go through it, and it makes total sense. But yeah, so those folks are thought to be more of a concussive effect than anything else. What really delineated a lot is physiologic margins. So now we got one part of the Venn diagram being the aircraft, and all the things that vary in there, it may not be completely malfunctioning, but it may not be optimally functioning, or we didn't tune the ECS to do smoother pressurizations, it's more of a jackhammer. But if you're healthy, never concussed before, fit, hydrated, really hydrated, again, hydrated, if you haven't been drinking too much alcohol, if you didn't smoke before the flight, all these things, you can tolerate some of that mechanical variance, but if you deplete or degrade those physiologic margins, your tolerance for variance in the aircraft goes down, and when those confluences come together, you start seeing physiologic events, right? Which really just means do what your grandmother told you, drink your water, don't smoke, don't drink too much, eat your vegetables, get some exercise, right? All right. So, and these are those margin degraders. So, let's think about them just real quick, for those interested in aviation medicine. The flight gear, when you put that, you strap that thing on, you cinch it all up, the harness itself is tight, so you start, you do restricted breathing, strapped breathing, then you put your harness to hold you in the ejection seat, and those ejection seats are hell, by the way, they feel terrible, you strap into that, and further, you're further restricted, so that's going to give you the propensity for a respiratory alkalosis, or hyperventilation just right there. You're crunched over a little bit, so you can get a little atelectasis. The atelectasis can be worsened by breathing pure oxygen and nitrogen not sustaining in the alveolus, all the oxygen being absorbed means the alveolus might collapse a little sooner, so you might have more atelectasis. The sitting position, there again with the volume, lower lung volume creating atelectasis, and even just being at altitude and being at a lower partial pressure, you need perfect lungs. COVID, oh my gosh, we got to do all kinds of tests to return aviators after COVID. Do all the aviators tell us that they've had COVID? All right, temperature. As it gets warm in that cockpit, you pant, right? What does your dog do? So panting is a way to offload heat, so there's another reason we're panting. Remember in the video, they talked about the strategic airbrake, right? When you're below 10,000 feet, we've learned to tell the aviator, take your mask off. We need to establish a lesser work of breathing, and we need to get some nitrogen back in the lungs. We need to normalize our respiratory cycle when we don't need the oxygen, okay? Oxygen's good, but I'm a hyperbaric dog. Oxygen is the first drug in pharmacology, and oxygen is toxic, right? The main thing about hyperbaric medicine is looking out for O2 toxicity, so oxygen's not pure good, but if you ask a layperson, is oxygen good when you're in an aircraft? Oh yeah, it's good, but it's not always good, right? So we had to learn that there's a place for it, and the strategic airbrake is simply that. In the hyperbaric chamber, it's kind of the same. I do airbrakes to give a break from pure oxygen, allow nitrogen back into the tissues, and in the aircraft, a strategic airbrake means take your mask off and just try to breathe without resistance, okay? Simple, but it took a lot of time and money to really figure that out. Results, it's good. Okay, there's your strategic airbrake. What other benefits? The reporting system, right? You turn attention to anything, the reporting system got better, more disciplined. More delineated. The role of hyperbaric medicine has been reduced, but at least better defined when we are going to use it. The roadshow that I, the long video brought the flight doc on board and improved confidence across the board, and then for, here's what's really important for our folks, is for the prolonged or concussive effect. They don't have to wait to get a referral. If you're not better in 72 hours, Bureau of Medicine and Surgery has a direct pipeline to the Tampa, hello, the Tampa VA, which is the number one polytrauma center of all the VAs with an insanely good TBI, traumatic brain injury program, and so if you come in with a prolonged concussive effect-related PE, you'll probably do three weeks as an inpatient, and you'll stay there until you're better, and the focus is not on, the focus is on retraining your neurocognitive baseline, just like we do for any other concussive patient. And the good news is, at this point, and again, 100% of aviators, I repeat, 100% of aviators diagnosed with this are returning to full duty without sequelae. Even at one aviator had four pressure-related PEs, but this was before we got the answers, but has now been rehabilitated and is back to work. Now, that's good for them because that's everything to them, that's everything they've ever wanted to do. It's good for us because we've all invested a lot of money in their training, and it takes years to develop a pilot to this level, and the more we can keep them safely flying, the better it is for all of us. And I tell you, being around seasoned reserve pilots who are flying airlines most of the time and then coming in flying fighters, they have so many hours in the cockpit, they're just, everything is second nature to them, so we want to keep the longevity of these pilots going. All right, so again, dehydration, I'm stressing dehydration, you might see that somewhere. One of the worst conditions for getting into any cockpit is dehydration, especially the fighter. One of the biggest things you can do to put yourself in negative physiologic margin. And what's the other best treatment for fatigue, sleep deprivation? The one thing you can do right now to make yourself feel better if you didn't get any sleep last night is hydrate, right? Get your blood volume up a little bit. Hydrate is a great answer, but in this situation, it is. So the term tactical dehydration, that means the aviator wants to not drink any water all day so they don't have to pee in a bag during their flight, is a big mistake. Let's look at the numbers. Often results in a 1% to 2% body weight reduction to accomplish that goal of not peeing in flight, but down at the bottom, it's easy to get a 3% decrease in body weight with these factors. At 3%, you get a 40% decrease in G tolerance. That's very significant, right? So we have to discourage our pilots, and even airline pilots, again, on the civilian side should learn from this. They are also professional athletes, and hydration is important. It's very, very important in aviation. Let's also look at the breathing gas itself. It's dry as a bone. It's just pulling water out of your respiratory tree. Your gear and mask increase the work of breathing, increase respiratory rate. In addition to the alkalosis effect, you're losing more water, right? So dehydration is just a real thing, and then it is aerobic and sweaty work. After heavy Gs, you can't help but sweat. You get a big sympathetic outflow. You sweat. Your blood pressure's changing. You're just losing a lot of fluid, and flying from Key West, just walking to the flight line and sitting there for the pre-flight checks, I probably dropped a half a liter of fluid into my flight suit, right? I mean, it's very real. Pilots sometimes forget this, and I think this was a great reminder to everybody in the community. Overall bottom line, the ideal tactical aircraft situation, aeromedical, healthy, fit, rested, hydrated, relaxed, educated, trained aviator, coupled with an aircraft that's proactively maintained with communication between the maintainers and the aircrew with continuous monitoring, and an environment that's less physiologically negative, less harmful, meaning smoother cabin pressurization cycles, clearly results in a vastly decreased risk of physiologic event. A few cases that do occur, again, expected to make what? 100% recovery. That's kind of the flow of this. You see back in 2011, there were low reported events. That was probably just because people weren't reporting. When people started getting aware of it, we peaked out there about two-thirds of the way in the curve by 2017. Probably the same number of events occurring, but people were reporting it. They were reporting it earlier, so we were catching the less than 72-hour folks, right? They weren't just going home and sleeping it off and saying, oh, I drank too much last night. They were beginning to know to report it, and now we're down to a much decreased rate with a less severe presentation when they do present. All right, bottom line, in current PE thinking related to HBO, though, and I learned that Bundy bias is a real thing, we're not that important. My beloved Naval Experimental Dive Unit sold me out, okay? But they said it, so I'll believe it. But there's still a potential blind spot, so let's put on, okay, there's still a role. So we got altitude, decompression, sickness, tables. It is possible, less likely in Navy because we don't fly as high as long. Air Force and the Space Force might have to deal with it more. Ah, arterial gas embolism. Let's put that over on a little table. My hyperbaricists in the room know where I'm probably going with that. Flyers who scuba dive before they fly and don't tell anybody, they might need to go in the chamber. Very high altitude operators, we said. And then, again, that clinical practice guideline, the Navy dive manual, neuroassessment, the concussion scale, and a question list that the doc down at Pensacola who runs the chamber and is the consultant will ask you. Currently, it's Captain Henry Casey, American superhero, who I will glow on here in just a second, and I was just on the phone with three times this week because he is my active duty counterpart, provided this and agrees completely with the things I'll say next, all right? So cabin pressurization, there's just an idea. So 18,000 feet cabin pressure is kind of that cutoff. Above that is when you start to be at risk for slowly fizzing nitrogen into your tissues. If there's not a massive decompression of that, like a canopy blow or something like that, or an ejection. So the little cycles in cabin pressure, though, again, are not thought to be enough to cause nitrogen fizz out, but enough to cause concussive effect, okay? but this is in those handouts that I provided to you if you're nerdy enough and HBO enough to want to look at that. 18,000 feet, what's magic about that? Well, let's do a little math, right? So one atmosphere of pressure is where we're at now. If I take you to another atmosphere down to 33 feet of seawater, one atmosphere is two atmospheres now total pressing on you. So at surface, I'm at one atmosphere. I go one more atmosphere below the water, that's 33 feet of seawater. So if I'm at 0.5 atmospheres relative pressure, that's about 16.5 feet of seawater differential. Now, if you're a scuba diver and you're bobbing in high seas and you don't breathe properly, you can do a pulmonary overinflation resulting in arterial gas embolism, not nitrogen fizz out, but bubbles breaking through capillaries and getting into your circulation, causing a stroke, cerebral arterial gas embolism. This is well-known to happen in seven feet of water, right? You bob from nine to two feet under the water and don't exhale or it happens rapidly, or you do it at the top of a compressed exhalation. You can blow a cap, alveolus and get an arterial gas embolism. Remember, think of your lungs in terms of this physiology as mylar, not latex balloons. You know the difference? So, right? A mylar balloon, you fill it up, it's done. It's not going any farther. That's our lungs. Our lungs are not latex balloons, right? So once they're full and you keep doing Boyle's law and pressure inverse to volume, right? Then you can blow. And so there's a bias among the flight surgeons and the UMOs, the undersea folks, agree that this bias might be a little problem because now that these recommendations have come out, the flight surgery community say, well, it wasn't above 18,000 feet. It can't be DCS or AGE. And our argument now is it could be either and even lower than 18,000 feet, if there's a significant and that's hard to define decompression event, you could have gotten a small arterial gas embolus with a shower of bubbles and result in an AGE, which should go into the chamber. Now, how are they getting away with this? Well, what are you breathing when that happens? You breathe in 100% O2. There's no nitrogen in that bubble, unlike regular air. So it's eventually going to be metabolized. But before it gets metabolized, you've had basically a transient ischemic attack. And that's where I'm concerned. We might have a blind spot. Now that's not evidence-based, but it's under sea medical officer kind of endorsed as something we need to be careful with. And so down at NAMI at the chamber, they like getting the calls to try to help tease this out. And so sometimes they'll recommend treatment and the flight docs like, just doesn't make sense. Doesn't make sense. Well, that's where the dual hat that Captain Casey and myself to a certain degree, the Al Bundy's say, no, there's still a little something here. Now, I'll tell you what I do. What would I do if a jet pilot presented to me at a level one civilian facility, hyperbaric facility with a canopy blow at 15,000 feet, but chest pain and neurosymptoms making me concerned for an AGE. Of course, I'd talk to the NAMI UMO to get a quick consensus, which is likely, because they're going to be on the same page, but I'd likely recommend and offer that patient hyperbaric treatment immediately with the U.S. Navy treatment table six, because it's not going to hurt anything. And if there was a shower embolus, then you might save them from some actual permanent brain damage. And then what about, but here's where it gets more, okay, so I did 5.6 G's, right? I did my anti-G straining maneuver and it looks like this. I'm doing an intense Valsalva. I'm squeezing my legs, my butt, and I'm holding my breath for a second. It's called Hicks Pixie. In that second, I'm restricting my lungs, right? So if there's a small, you know, a small pressure differential in that moment, I'm even a little bit more at risk. Now, I agree with the entire Navy pathway. I agree that most of the time that's not where we're at, but as a hyperbaric doc who might be, you know, called about this or a flight surgeon who might be invested in care for my squadron, I wanna keep this in my back of my mind. And if you're an FAA examiner or a civilian hyperbaricist, it's possible you could be asked this question. My mantra in the hyperbaric world is always, when in doubt, press it out. They presented to me, it looks, smells like it might be DCS. I'm gonna press them because we got a time to treatment as tissue window, right? And we'll talk about how to pull that off here in just a minute. Hope I'm making sense. Well, 10 minutes, yeah. There's not complete agreement between the UMO and the flight surgeon community. On your slides, if you ever were confronted with this problem, there's the hotline for the Naval Aeromedical Institute's undersea medical officer with the dive chamber. Probably less than 2% of people in this room even touch that world closely enough, but at least I'm providing that to you. All right, salute to Captain Henry Casey, super American hero, started out as a SEAL, senior chief SEAL and corpsman. At 42, he was my class leader at Navy Diving Medical Officer School as he mustanged up and gone through it. Navy diver also, because he was a senior chief, he knew how to rig the system. He also got himself through flight surgery school. He was the officer in charge of the flight surgery school just before I went, and now he's the guy staffing the chamber. So he's a perfect dual hat. He's the true undersea to top of the stratosphere guy. And I just consider him my big brother and look to him for all kinds of information. And as my pilots say, other fighter-y, pilot-y stuff. What we can learn, remember, all high-speed operators are professional athletes whether they treat themselves that way or not. And my pilots like it when I tell them, dude, you are a professional athlete. There is nobody, well, you're better, a golfer. You're performing at a much higher level with much more intense physiological demands. And of course, we sit and do our flight physical. They tell me one thing, and then when we're all out together, they're like, doc doesn't see this. I'm like, roger that. So we'll talk about that occupational medicine thing here in a second. The other thing is neck and back pain. You might see this rolling over, especially among your reservists on both fronts. And it's real, it's real. You saw the strain when you come to a stop. The seats are very uncomfortable. The gear is heavy. It gets you into an unnatural position. They're riddled with trigger points, very classically. I don't know if they have an increased rate, but in my group, in the reserve group, they're starting to get some degenerative changes and we're working through that. But it's very real. I want my pilots to think like a wrestler. I want them to warm up the neck before a flight and to stretch and strengthen during part of their routine fitness. And they're starting to take me more seriously now that I've gained their trust. And I'm going to be working that. I've got a aerospace physical therapist we're going to put together a plan. Okay, so I've got eight minutes left. Let me see, I got the... All right, I'm just going to give you a quick hint at what Navy divers and Navy dive docs undergo. If you haven't seen this before and you're all into hyperbaric medicine, are they seeing this, Jeff? And I heard, as it were, the noise of thunder. One of the four beasts saying, come and see. And I saw. And behold. It's not my class, but I'll do the same thing.

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