The High Pressure Experiments That Made D-Day

Summary

Fresh Air – "The High Pressure Experiments That Made D-Day"

Original air date: November 14, 2025
Host: Terry Gross
Guest: Dr. Rachel Lance, biomedical engineer, blast injury specialist, and author of Chamber: The Untold Story of the D-Day Scientists Who Changed Special Operations Forces Forever
Guest background: Former U.S. Navy engineer and researcher at Duke University specializing in underwater physiology and blast injuries.

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Episode Overview

This episode of Fresh Air explores the remarkable and perilous work of WWII-era scientists who performed risky underwater and pressure experiments on themselves to solve the unprecedented physiological challenges posed by submarine warfare, deep-sea diving, and D-Day reconnaissance. Dr. Rachel Lance, author and researcher, discusses the story behind these "chamber divers," their contributions to special operations forces, and the legacy their experiments created for modern hyperbaric medicine, diving technology, and safety standards.

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Key Discussion Points & Insights

Rachel Lance's Path to the Story (01:53–02:52)

• Lance discovered the story while reading a 1941 paper on carbon dioxide by British scientists during the London Blitz.
• The realization: Scientists saw CO₂ management as critical, enough to work through bombings.
• Quote (Lance, 02:01): “Something about carbon dioxide was so critical to them that they were looking at it while they were being bombed.”

The Origin of WWII Underwater Research (02:55–03:59)

• Initial focus was submarine survival after a string of submarine losses in 1939.
• Led by J.B.S. Haldane at UCL, the group tackled life support in subs: air handling, escaping, and rescue.
• Research expanded to include diving physiology—culminating in technologies crucial for D-Day beach reconnaissance.

Hyperbaric Chamber Experience (04:20–05:30)

• Modern and historical chambers simulate underwater pressure; Lance describes being inside as "loud" and "enclosed."
• Chambers allow both pressure increase (as in diving) and decrease (as in altitude); heat and cold shift rapidly; gas flows and constant noise predominate.

Physiology of Pressure & The Bends (06:10–08:24)

• Every 10m underwater adds an "atmosphere" of pressure.
• Major danger: decompression sickness (the bends), where rapid ascent causes nitrogen bubbles in tissues.
• Quote (Lance, 07:39): “In the most extreme manifestations, you can get bubbles everywhere… In the brain, spinal cord, liver, and joints.”
• Mystery remains where these harmful bubbles originate; no clear correlation between observed bubbles and symptoms.

Experimental Ethics—Then & Now (09:15–12:01)

• WWII researchers performed dangerous, illegal-by-today’s-standards experiments on themselves, often suffering the bends, seizures, even spinal fractures.
• Lance underscores strict modern safety and ethical rules, highlighting the difference in how adverse events are handled today.
• Quote (Lance, 12:01): “If I tried to do that, even if I had subjects who consented, I would possibly be criminally prosecuted.”

Real-World Incidents: The Brooklyn Bridge (13:32–15:42)

• Early caisson workers experienced decompression sickness before anyone understood the cause, leading to many deaths.
• Haldane’s interest in diving safety arose partly from these early tragedies—prompting research that made modern decompression sickness preventable.

Oxygen Toxicity—Danger in the Deep (16:07–18:31)

• Surprising finding: “Fresh air becomes poisonous deeper than about 200ft.” (Lance, 16:17)
• High pressure makes oxygen chemically aggressive, causing cell damage, visual disturbances, seizures, and potential death.
• Oxygen's “volatility” is both life-sustaining and, in excess, destructive.

Antioxidants and Oxygen (18:31–20:09)

• Antioxidants react with oxygen’s extra free radicals, but dietary supplements are vastly insufficient under diving conditions.
• Lance (half-humorous): “... it was something like 180 bottles of merlot per breath that the diver would have to drink...” (19:35) to counteract oxygen toxicity at depth.

Blast Injuries: Underwater vs. On Land (21:58–24:42)

• Water mitigates burns and shrapnel but transmits shockwaves much more efficiently than air.
• Underwater blasts cause mostly internal injuries, often surprising since there may be no visible wounds.
• Quote (Lance, 23:24): “It’s more that they travel straight through you. It’s even more sci-fi than just a standard impact…”

WWII Chamber Divers and Self-Experimentation (25:50–26:31)

• In the war’s intensity, scientists and volunteers exposed themselves to controlled underwater explosions to study injury mechanisms.
• Horace Cameron Wright, notably, would check his own lungs for blast damage after detonations.

Technological Advances for D-Day (28:14–30:21)

• Scientists pioneered the use of mini-submarines ("X craft") for clandestine Normandy beach reconnaissance.
• Chamber experiments led to workable limits for oxygen and CO₂ scrubbing—directly enabling critical mapping missions before the invasion.

Hyperbaric Medicine—Promise and Controversy (30:21–32:24)

• Proven effective for conditions marked by poor tissue oxygenation, such as diabetic ulcers and radiation burns.
• Sometimes misused for conditions where evidence is lacking (e.g., autism, chronic traumatic brain injury).

Personal Experience: Hyperbaric Therapy in Action (32:24–34:08)

• Lance recounts a dramatic case of a diver with an air embolism who “woke up” and recovered after hyperbaric treatment.

Sea vs. Space Research (34:08–36:49)

• Extreme underwater and space environments share similar human and engineering challenges: pressure differentials, life-support, risk of decompression illness.
• Cross-pollination between Navy, NASA, and high-altitude aviation is common.
• Conferences often combine space and deep-sea medicine due to shared technical obstacles.

The Moral Stakes of Military Research (36:11–38:13)

• Lance’s primary motivation is safety and saving lives, not weapons development.
• Real-world impact is always present in her mind—particularly given her interactions with military personnel.

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Notable Quotes & Memorable Moments

• “Something about carbon dioxide was so critical to them that they were looking at it while they were being bombed.” — Rachel Lance (02:01)
• “If I tried to do that, even if I had subjects who consented, I would possibly be criminally prosecuted.” — Rachel Lance on WWII-era research practices (12:01)
• “Fresh air becomes poisonous deeper than about 200ft.” — Rachel Lance (16:17)
• “It’s more that they [shockwaves] travel straight through you. … Sci-fi.” — Rachel Lance on underwater blast injuries (23:24)
• “So using the work by these scientists, they had the subs full of carbon dioxide scrubber. They knew what their safety limits are. … Waited to see how long they could physically handle the amount of carbon dioxide in there before they ended up with migraines and projectile vomiting. Great experimental endpoint.” — Rachel Lance on D-Day preparations (29:15–30:10)
• “The lungs can handle a surprising amount of injury long term. … I think he just took some days off and then tried again, to be honest.” — Rachel Lance on Horace Cameron Wright’s self-experiments (26:31)
• “I work on safety standards and safety equipment, and I’m motivated by that daily.” — Rachel Lance on her work’s purpose (38:08)

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Timestamps for Key Segments

• 01:53 – Introduction to Rachel Lance and her research origins
• 02:55 – Submarine disasters catalyzing WWII physiological research
• 04:20 – What a modern hyperbaric chamber is like
• 06:10 – How water pressure affects the body, the physiology of the bends
• 09:15 – Ethical constraints: experiments past vs. present
• 13:32 – The Brooklyn Bridge and first cases of decompression sickness
• 16:07 – Oxygen toxicity at depth and why "air" can kill
• 18:31 – Antioxidants: hype vs. real utility in diving
• 21:58 – Underwater vs. land blasts: how water changes injuries
• 25:50 – WWII chamber divers experimenting on themselves
• 28:14 – Technological innovations leading up to D-Day success
• 30:21 – The uses, misuses, and future of hyperbaric medicine
• 34:08 – Parallels between deep sea and space research
• 36:11 – The ethics and impact of military biomedical research

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Concluding Reflections

This episode offers a riveting account of extreme scientific courage, innovation under fire, and the historical roots of modern underwater and pressure medicine. Rachel Lance provides a humanistic window into the hazards and heroics of WWII's "chamber divers," highlighting how their willingness to risk—and sometimes sustain—life-altering injuries became foundational to saving countless others, both in war and peace.

Their story not only reshaped D-Day but continues to animate cutting-edge medicine and safety standards for divers, submariners, astronauts, and anyone challenging the planet’s most hostile environments.

Transcript

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[David Biancooli]

This is FRESH AIR. I'm David Biancooli. Veterans Day has us thinking about our interview from last year about some brave and obsessive scientists. Before and during World War II, they did underwater research, which was essential to the success of D Day, when allies had to conduct surveillance searching for traps and mines underwater and on the shore before storming the beach at Normandy. We're going to listen back to Terry's interview from last year with Rachel Lance. She wrote the book titled Chamber the Untold Story of the D Day Scientists who Changed Special Operations Forces Forever. She's a biomedical engineer and blast injury specialist. Some of her research revolves around the how can the human body survive the extremes of the deep sea? And how do blasts and bombs underwater affect the body compared to the impact of blasts on land? For several years, Rachel Lance was an Engineer for the U.S. navy, researching and testing new underwater technology For Navy divers, SEALs and Marine Force Recon personnel. She also conducted research at Duke University using their hyperbaric chamber. That's an enclosed chamber in which the air pressure can be increased or decreased along with the levels of oxygen and other gases to simulate the extremes of underwater environments, monitor the negative impact on the human body, and test solutions. In order to do the research. The scientists during World War II put themselves through extremes in the hyperbaric chamber and sustained some fairly serious injuries.

[Terry Gross]

Rachel Lance, welcome to FRESH air. What were you researching that made you interested in the World War II underwater research?

[Rachel Lance]

I read this paper about carbon dioxide, and it wasn't extremely exciting. It concluded essentially that carbon dioxide is bad for you and it hurts, which I already knew, but something about the date bothered me. It was published in 1941, which was obviously wartime, and it was published by a group of British scientists in scientific research. The paper usually comes out about a year after the research was done. So that meant that these people were working on this question of carbon dioxide in 1940 in London. The other thing that was happening at that time period was the blitz. So something about carbon dioxide was so critical to them that they were looking at it while they were being bombed. From there, I just kept pulling at the thread until the entire story became evident of what they were actually working on.

[Terry Gross]

So tell us more about what they were actually working on.

[Rachel Lance]

They started out looking at submarine survival. So The Allied militaries had built all these submarines in preparation for World War II because they essentially knew some sort of conflict was coming. But in the summer of 1939, three of them went down in rapid succession. There was the US Escuelas, the HMS Thetis, and the French Feigny, which still remains lost. However, when these submarines sank, the Allies realized that they didn't know very much about surviving inside them, escaping them, or even what to do if one of these accidents occurred. So this research group that I was following, which was based out of University College London UCL and led by a scientist named JBS Haldane, we're looking at these problems of undersea survival, of how people breathe inside enclosed spaces and how people need to treat these breathing gases if they want to stay in these enclosed spaces on purpose. Eventually that transitioned into diving and diving technologies, and all of those things together were used to scout the beaches of Normandy and facilitate the landings of D Day.

[Terry Gross]

So in order to do the research, the scientists conducted research on their own bodies in hyperbaric chambers. I give a very cursory description of a hyperbaric chamber. You've been in one at Duke. They have a state of the art hyperbaric chamber. Tell us more about the chamber and what it's like to be inside of it.

[Rachel Lance]

It's loud. It's hyperbaric. Yeah, it's loud. That's my strongest impression.

[Terry Gross]

Yeah.

[Rachel Lance]

Ah, the opposite. The hyperbaric chamber is essentially a gas pressure vessel. So you're basically inside a scuba tank. Now, our scuba tanks at Duke are very fancy. We have seven of them all connected together. So it is like being inside of a little hamster tube village. And ours can go to either high pressure or low pressure, but in that process, you have tons of air and gases moving through the piping. So that's my biggest impression is you're in this enclosed space. They're always either circular, spherical or cylindrical because that's a stronger shape. And then you constantly have noises, you constantly have gas flow. As you're pressurizing, it gets really hot really quickly. As you ascend the other direction, it gets really cold really quickly. And then you have people on the outside who are monitoring the gas composition in there. When you're in an enclosed space to make sure you're breathing safe levels. So, yes, the biggest sensory takeaway from a hyperbaric chamber for me is probably the noise.

[Terry Gross]

So one of the things that happens in the hyperbaric chamber is that you can increase or decrease the pressure. So when you're underwater is all of the increased pressure from the weight of the water.

[Rachel Lance]

Pretty much we have one atmosphere that we breathe. That atmosphere of gas we forget about pretty often, but it does sit on top of us all the time. Once we go under the water, we have additional atmospheres that essentially get piled on. So every 33ft or 10 meters, if you're metric is equal to another atmosphere of pressure, the deeper we go, the more that pressure increases, simply from the weight of that water pushing down.

[Terry Gross]

And that's really dangerous to the body, as the researchers found out. What does it do to the body to have that much pressure on top of you? And the real problem comes in if you emerge from the depths too quickly, you get what's known as the bends. Why does that happen?

[Rachel Lance]

That's the million dollar question, isn't it? Basically, the human lungs are very weak. They're not a strong organ. And so they're really good at what they do in terms of processing gas, but they do it passively. So they essentially just let that gas flow come in and out of the body. What that means for breathing is that when we breathe a gas, we have to breathe the gas of the approximately same pressure as the air around us or the water around us. When you're underwater, that means you're breathing high pressure gas. That means that that increased pressure can help those gases absorb into your bodily tissues. The air around us is about 78 to 79% nitrogen. So as we're underwater and we're breathing that higher pressurized gas that nitrogen and the other gases absorb into our tissues, what you described with decompression sickness, the bends, that's when we come back up, we go to those reduced pressures too quickly. The nitrogen comes out instead of harmlessly in the bloodstream processed by the lungs, it comes out as bubbles. That's really bad. It causes all kinds of physiological issues.

[Terry Gross]

Oh, so you get bubbles in your lungs and bubbles in your blood.

[Rachel Lance]

In the most extreme manifestations, you can get bubbles everywhere. There are case reports of bubbles in the brain and bubbles in the spinal cord, bubbles in the liver and in the joints. Those are the extreme cases. One of the really interesting mysteries about decompression sickness is that we don't actually know where the bubbles originate from. Bubbles in the bloodstream are not related to the actual symptoms of the disease itself. So you can have a person in extreme pain with very low levels of bubbles in their bloodstream, and you can have people with lots of bubbles in their bloodstream who have no pain and no other signs of issues. So one of the things that I research at Duke and in hyperbarics in general Is trying to figure out where these bubbles are coming from in the first place.

[Terry Gross]

How do you find out?

[Rachel Lance]

Sometimes it feels like magic. Anytime you're looking at the human body. How do you find out is the key problem. You have to be creative with instrumentation, with imaging, with testing, with looking at indirect metrics, so that you can try trace these mysteries and these sources of injury Back to their origin without doing further damage to the person you're studying. A lot of what I do at Duke Involves the creation and the development of new products and new methods that work under pressure and work at depth. Because when we're in that extreme isolated scenario, in this incredibly thick metal container, we don't have access to most of the tools of the rest of the hospital.

[Terry Gross]

You know, I'm thinking of the scientists during World War II who exposed themselves to extreme pressure in the hyperbaric chamber, and some of them got really sick. They basically had the equivalent of the bends, that decompression illness. You're not going to do that to yourself, and you're not going to recruit human subjects to get really sick. So what kind of body can you study?

[Rachel Lance]

We try to flirt with the line of danger, but never cross it. That's a big rule that complicates the study of injury, Biomechanics in general. And that's something that I encounter a lot with blast trauma. There is a gentleman in this book in chamber divers Named Horace Cameron Wright, and he encountered that same issue. He wanted to look at underwater explosives. Well, he didn't feel ethically comfortable Putting other people down and risking them get injured. So he decided to go himself. When we're looking at these problems, we have that same ethical conundrum where we can't intentionally injure someone. We can only take advantage of cases where people have injured themselves. And so those cases are very valuable. Whenever people have an accident in the real world, that's a big part of data collection. That's a big part of what I study. And then when we're in a controlled environment, we try to use what we do know in order to subject people to perhaps more than what we consider to be totally safe. But stop short of what is dangerous with the knowledge that we're literally in the exact right facility to treat them if something bad does happen. That was true with the chamber divers as well. When they got decompression sickness, when they had major problems, they were already in the chamber, which is also the Exact right way to treat these problems. And so it was better for them to experience it than for the World War II military personnel defense. Get it out in the field.

[Terry Gross]

You just mentioned if you get the bends from experiments in the hyperbaric chamber, the hyperbaric chamber is the best place to be to cure the bends. And is that because the pressure can keep gradually being adjusted, just as divers have to do, which is to slowly emerge and stop occasionally in the water so that they don't suddenly change the pressure?

[Rachel Lance]

Yes, that's exactly right. So if someone comes up and they start to show signs or symptoms of decompression sickness, they can be recompressed in a hyperbaric chamber. Now we're increasing that pressure around them back to a higher level. And the theory is that shrinks the bubbles in their bodies back down so that we can bring them up more slowly at a safer and more prolonged rate and let the nitrogen come out in a harmless fashion.

[Terry Gross]

So what are some of the extremes that The World War II researchers exposed themselves to in the hyperbaric chamber? What experiments did they conduct on themselves?

[Rachel Lance]

Oh, my gosh. They put themselves in there for things that would not be legal today. If I tried to do that, even if I had subjects who consented, I would possibly be criminally prosecuted. They were putting themselves in there and breathing pure oxygen and rocketing the chamber down as quickly as they go to see if they could kind of outrun the negative effects. They were taking some of these gases like oxygen down to depths that we now know are extremely dangerous and toxic. And they were continuing to do this even after they were having severe injuries. With modern research, we have what are called serious adverse event reporting requirements. So if something bad happens in our research, we have to sit down and have a conversation about the ethics of asking people to continue. Whereas this group, because their goal was to prevent military deaths during the invasion of Normandy, they figured, better we do it here in the lab. And so they just kept exposing themselves to this over and over, especially these high oxygen pressures. They were having seizures. They were breaking spines. Two of them broke their spines. They were dislocating their jaws. One of them, Helen Spurway, dislocated her jaw five times in the same dive, and they kept going. These are things that would be wildly unethical and illegal today. And they were doing it because they were in this context of the Blitz and the bombings and the horrors of World War II happening around them.

[Terry Gross]

You know, one thing, one thing. One of the many things I found really fascinating in the book was that in the early 1900s, when the Brooklyn Bridge was being constructed, the people there, the men who were working underwater during the underwater part of the bridge, they got the bends before anybody knew what the bends were.

[Rachel Lance]

Right.

[Terry Gross]

And so you had all these men getting, like, super sick or dying, and nobody understood why.

[Rachel Lance]

Nobody knew. And this is classic with the world of injuries in extreme environments, you don't know what's going to be a problem until somebody goes first. And that's true. With so much of science, with so much of testing and the amount of research that we do, people have been talking about artificial kidney and kidney transplant from a pig and the ethics of that. And the brutal reality is you can do benchtop testing until you die, but nobody really knows what will happen in a human body until, like, the Brooklyn Bridge, someone just goes first. And so those unfortunate caisson workers, yeah, they were the first ones who were really experiencing decompression sickness and experiencing how brutal and lethal that can be.

[Terry Gross]

Was the cause of their sickness discovered in time to save other men from dying?

[Rachel Lance]

Not as far as I'm aware. For the bridge, they sort of just powered through. They were having all these deaths, and they just hired more workers, which is perhaps why a lot of the workers there started quitting toward the end of the project. But after that, it was used by the scientific and research community as an example of a thing to stop. This is kind of why a lot of us, myself included, get into science. When we see things happening, we have the drive to explore them, understand what's happening, and then try and prevent the next case from going on. So the Haldane saw these cases. JBS Haldane's father saw these cases and then used that to start researching diving in a more controlled way. So now decompression sickness is extremely preventable.

[Terry Gross]

You know, I don't think I'll ever drive across the Brooklyn Bridge again without thinking about this story.

[Rachel Lance]

I hope not. Somewhere down there. Yeah, somewhere down there are wooden caisson shelves and in which people worked until they literally died. And I think that's incredibly powerful in terms of remembering the context of where our society comes from and how it's been built.

[Terry Gross]

Something I'd really like to have you explain. You explain why too much oxygen can be deadly when you're breathing.

[Rachel Lance]

Did you know fresh air becomes poisonous deeper than about 200ft?

[Terry Gross]

Wait, repeat that. Fresh air becomes poisonous below 200ft.

[Rachel Lance]

Right. Air is roughly 21% oxygen. So since oxygen can become toxic when you elevate the pressure, the 21% oxygen becomes toxic if you're diving deeper than about 200ft below the surface of the ocean.

[Terry Gross]

So what is it about the oxygen that can become toxic or even deadly? And if there's the wrong proportion of it and there's too much of it?

[Rachel Lance]

Our bodies use oxygen because it's extremely chemically reactive. Oxygen is one of these weird molecules that sits on the periodic table in a location that just makes it react with everything. We take advantage of this to build fires. That's why oxygen is needed for fires. We take advantage of this to design explosives. That's how we design explosives. And our body internally produces energy using oxygen in pathways that are not terribly dissimilar. So what happens when you have too much oxygen is essentially that volatility turns against us. It can start to act on your lungs. It can start to kill the cells of your lungs. It definitely starts to act on your nervous system. So once you get beyond a certain pressure and concentration of oxygen, your nervous system can no longer defend itself against this essentially onslaught of reactivity. And you begin to have these really intense symptoms that if you don't remove the oxygen levels, will eventually kill you.

[Terry Gross]

What kind of symptoms?

[Rachel Lance]

It starts with minor muscle twitches. So people might have small twitches in their fingers or in their arms. One of the common ones is the upper lip. You kind of get a little elvis thing going on. People start to have visual disturbances. The eyes use a ton of oxygen, and so they're one of the more sensitive measurements that we can have to when our breathing gas levels are going awry. So people start to hallucinate bright flashes or have twitches of their eye to the left and right. Eventually it's going to escalate to seizures. And then from there, if the oxygen levels are not removed, then you'll have death.

[Terry Gross]

This is a little bit of a sidebar, but you talk about it in the book, and I think everyone will want to know this, Because a lot of people buy antioxidants As a kind of vitamin supplement, and they're widely advertised. So how does that relate to what you're telling us about oxygen, if at all?

[Rachel Lance]

Antioxidants are chemicals that react with oxygen and sort of neutralize it. So when we eat them in food, the theory is that the antioxidants we're consuming will react with the oxygen that's sort of extra in our bloodstream and neutralize it from having some of the more negative effects that can accumulate over time, like aging. Oxygen is thought to be the reason that we age. The problem is dosage. So the antioxidants in food I actually it took me a lot of work to do this math, but I calculated the concentration levels of antioxidants in the most, most popularly cited antioxidant based foods and they don't have the sufficient concentration to really make a difference. I did the math for a while. They were at pressure and I don't remember the exact number off the top of my head, but it was something like 180 bottles of merlot per breath that the diver would have to drink in order for the antioxidants to have an actual effect in neutralizing the oxygen. Don't get me wrong, I'm gonna eat dark chocolate and blueberries forever, hopefully. But I'm not convinced that there's enough of the chemical substance in them to.

[David Biancooli]

Actually make a Rachel Lance speaking to Terry Gross in 2024. After a break, we'll hear more of their conversation. And Justin Chang reviews Seurat, the new movie from Spain he calls one of the best films he's seen all year. I'm David Biancooli and this is FRESH air.

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[David Biancooli]

Hey, it's Ray from Car Talk. Are you tired of all the depth and thoughtful care that goes into NPR shows? Want some good old fashioned goofing around and stumbling to figure out what's going on? Well, I've been taking occasional car questions again. You can hear them by signing up for NPR along with lots of other bonus content. Just go to plus.NPR.org you ever get.

[Rachel Lance]

To the pharmacy and you're expecting your medication to cost 20 bucks, but instead it's 200 or 1,000 and you're like, wait, really?

[Various NPR Announcers]

Like, are you sure?

[David Biancooli]

Is there some kind of mistake?

[Rachel Lance]

This week on the Life Kit podcast, what to do when youn Prescription Costs Way More Than youn Expected. You can listen in the NPR app or wherever you get your podcasts.

[Terry Gross]

Let's Talk about blast injuries in water, deep sea water versus on land, because you are a blast injury specialist. What are some of the differences in terms of their impact on the body?

[Rachel Lance]

There are two major differences. The first is that we don't have to worry about some of the things that we do on land, such as shrapnel and burns, because the density of the water slows down a lot of those effects before they can reach more than a meter or two. The other big difference is that we have to worry a lot more about the shock wave. In air, the shock wave decreases very quickly, but in water, just like sound, it travels a lot more readily. And so imagine how far away you can hear whale sounds. You can hear whale sounds for miles and miles. The same type of impact, where the density of water moves these waveforms along more efficiently than in air, occurs with the shockwave from explosions. So you see different injury patterns from the underwater explosives, but most of them tend to be internal, which is kind of terrifying.

[Terry Gross]

Why are they internal and not X? Oh, because there's no object that's piercing the skin. It's just the blast waves.

[Rachel Lance]

It's just the physics of the shockwave.

[Terry Gross]

So the shockwaves like push into you and injure you internally. Is that what's happening?

[Rachel Lance]

It's more that they travel straight through you. It's even more sci fi than just a standard impact. So they don't carry with them a lot of force. So the actual force from a shockwave is not very strong. But what happens is you go from zero pressure around, or whatever ambient pressure you're at, to the highest level of the shock wave and it happens in zero seconds. The metaphor I like to use is a car. Imagine you're in a car, you're at a full stop, and then all of a sudden you're going 60 miles an hour with zero acceleration. This doesn't sound very pleasant. The same risk of injury occurs because of that sudden impact and that sudden infinite rate of pressure increase with the shock wave. So as the wave is traveling through you, it can actually travel through most of the body fairly easily. Like the arms and the legs, below a certain threshold, it'll just pass through them without a lot of harm. But the lungs and any other gas containing organs have that air. Again. We talked about how sound travels more easily underwater. Now it's hitting air. So at the surface of those air pockets, you have an effect called spalling, which is essentially where the shock wave is forced to slow down and you get this spray of blood that goes into Those gas pockets.

[Terry Gross]

I wonder how it feels. People usually like, look for a bruise or a wound or, you know, and there's nothing to see, I suppose, unless maybe there are bruise marks.

[Rachel Lance]

That's part of what happened at the start of World War II. A lot of people were in the water because there's so much naval combat happening. There were U boats terrorizing the Atlantic. And these ships would go down, including like the USS Midway and the USS Yorktown would go down and they would have their sailors waiting in the water. And then either a depth charge would go off or the U boat would set off for a torpedo and that shockwave would travel and hit the sailors. Then all of a sudden you've got sailors in the water with massive internal bleeding and no external signs of injury. So this was a huge mystery at the start of the war. That had been really understudied and the physicians and the scientists were kind of scrambling. It was the same thing as trying to survive underwater. They and in the submarines, they were hit by all of this new technology. They didn't know what was going on and they had to study it all at once.

[Terry Gross]

How did they study it?

[Rachel Lance]

They basically looked at what we look at today, which is people who have already been hurt through circumstances other than intentional introduction. But then because the war became so severe, that's when you start to see people experimenting on themselves. So that's when you start to see the chamber divers getting in their tubes and you start to see horse Cameron Wright climbing into the lake along with dozens of volunteers to blast themselves.

[Terry Gross]

Right. Exposing themselves to the shockwaves of TNT underwater.

[Rachel Lance]

Exactly. When Horace Cameron Wright climbed out of the water, after each explosion, he would use a stethoscope to measure where in his own lungs there was blood.

[Terry Gross]

How did he survive that?

[Rachel Lance]

The lungs can handle a surprising amount of injury long term. I'm not sure how he survived himself, but the lungs can handle up to 15% injury or so without having severe symptoms. Like if you try and sprint, you'll probably have an issue, but you can have low grade levels of damage to your lungs and still be okay. So I think he just took some days off and then tried again, to be honest.

[David Biancooli]

Rachel Lance speaking with Terry Gross last year. More after a break. This is FRESH air.

[Rachel Lance]

This week on Consider this an encrypted.

[Rachel Martin]

Group chat where members of the National Guard are processing President Trump's actions.

[David Biancooli]

This is just not what any of us signed up for.

[Rachel Lance]

And I just wonder, like, who's gonna.

[David Biancooli]

Stand up to this?

[Rachel Martin]

Plus, what's next for congressional Democrats after their move this week to release more of Jeffrey Epstein's emails. Listen this week to consider this on the NPR app or wherever you get your podcasts. This week on the NPR Politics podcast, the latest on Democrats in some blue states. Redistricting a lot is still uncertain, but.

[Rachel Lance]

The picture moving into the midterms for Democrats isn't looking as bad as it once did.

[Rachel Martin]

Plus, the government shutdown is over. What's Congress focused on next? That and more daily political coverage on the NPR Politics podcast. Listen on the NPR app or wherever you get your podcasts.

[Various NPR Announcers]

Fall in love with new music every Friday at All songs considered. That's NPR's music recommendation podcast. Fridays are where we spend our whole show sharing all the greatest new releases of the week. Make the hunt for new music a part of your life again. Tap into New Music Friday from All Songs Considered available wherever you get your podcasts.

[Terry Gross]

So what are some of the solutions that the World War II scientists came up with to help the military conduct underwater surveillance during World War II just before D Day? So that and this was critical to the success of D Day.

[Rachel Lance]

One of the big things that these scientists contributed was the improvement of their ability to use not only regular sized submarines, but miniature submarines. These tiny subs had a smaller gas volume, which made the rules of breathing physiology even more time critical. And the scientists who were conducting these experiments on themselves were really the ones responsible for determining how much people could tolerate carbon dioxide buildup in there, how much chemical scrubber material they needed to bring with them in order to remove carbon dioxide to fulfill their missions, and how much oxygen they also needed to carry as well. So when we had the development of these mini subs called X craft, they were then used by the British to start scouting the beaches of Normandy because the tiny submarines, which were only about 10ft tall, could get so much closer and they could dive down to the bottom and wait offshore for night to come back around again. So using the work by these scientists, they had the subs full of carbon dioxide scrubber. They knew what they're SAF limits are, they knew what to do with the oxygen levels and they would go over to Normandy in advance of D day and sink down to the bottom during the day, breathe inside their safe enclosed environment, and then come up at night, crawl ashore, measure the sand, measure the beach angles, provide detailed maps, everything, and then go home. A lot of that credit can be due to this research lab at ucl, who again did this experiment by just putting themselves in a tank, closing the door and Waiting to see how long they could. Could physically handle the amount of carbon dioxide in there before they ended up with migraines and projectile vomiting. Great experimental endpoint.

[Terry Gross]

There's something called hyperbaric medicine, and we talked about what a hyperbaric chamber is and how it's used for research to simulate the environment of the deep sea so that researchers can understand what happens when the human body is exposed to the extremes of the deep sea. There's something called hyperbaric medicine. How is that used? Like, outside of the World War II, researchers who became ill because they exposed themselves to those extremes. How is hyperbaric medicine used?

[Rachel Lance]

Hyperbaric medicine is a field that has both amazing effects and amazing controversy at the same time. It has proved to be really excellent for disease states where the issue is not enough oxygen. If you think about it, that makes sense. You pressurize the patients, you give them oxygen, you're forcing more oxygen into their bodies. So some of the cases that it's extremely helpful for are things like diabetic wounds. So these wounds become ulcers. They have a difficult time healing because diabetic patients tend to have poor circulation in their limbs. With hyperbaric treatment, they get the oxygen they need at that site to help those heal. The same thing is really useful for cancer patients who have radiation burns if their immune systems are compromised by chemotherapy or simply just the trauma of the lung. Invasive cancer treatment, the radiation burns show a lot of responsiveness to hyperbaric compression because it forces oxygen to that wound site and allows them to heal. There's also some controversy about hyperbaric medicine because since it tends to be pretty harmless, like if you're pro. If you're pressurizing people under a known medical treatment table, there really aren't negative long term side effects to be spoken of. It sometimes then tends to get used by charlatans. So it's been used to treat both autism and chronic traumatic brain injury, both of which have huge bodies of evidence showing that it does not help.

[Terry Gross]

Early in your career, maybe even before you had a career, you watched hyperbaric medicine save a father's life. Can you tell us that story?

[Rachel Lance]

Yes. That was when I was living out on Catalina island, and that was my first hyperbaric chamber, little baby Rachel. And I was out there as a volunteer. That's a completely volunteer run chamber. So, yeah, I'm actually happy to give that a shout out because they do run on donations. But I was out there volunteering, volunteering to treat diving accidents. And we had a diver that Came to us because he had either accidentally or something happened during the ascent. But he had an air embolism, which is what happens when you don't exhale properly. And the air expands as you go up. And it can rupture your lungs and travel into your body. A lot of the times these can be fatal. If they're not properly treated. And quickly, they can have very serious negative consequences. And this gentleman was a man who had experienced an air embolism. He was brought to our chamber, and we pressurized him. And once he got under pressure, he just kind of woke up. He had gone in blue. And I'm not exaggerating, this was not a human skin color. And I will always remember how he looked. It was this deep, bluish purple. And he went in, and the bubble shrank under pressure, and he returned to normal. And by the time he left, he was not only walking and talking, but, perhaps more importantly, breathing in with a heartbeat.

[Terry Gross]

Most of your research has been about the human body in a deep sea environment, Whether in a submarine or just exposed in the water with a. Obviously with a suit on and a tank and all of that. But you've also done some research about outer space. Can you talk about some of the similarities and some of the differences between what you have to face as a researcher. When you're looking at space versus sea?

[Rachel Lance]

The most important similarity is the difficulty of the environment, not just on the human body, but on any instrumentation you want to bring in when you're doing research. So the biggest obstacle with both of these worlds. Is the engineering of products and devices. In order to measure the things we even want to ask the questions about. So working in the hyperbaric chamber, the limitations on what I'm doing and what I'm building, It works for both environments. And that's why, working with the Navy, we collaborated frequently with NASA. We were talking frequently with people building the high altitude breathing systems for jets, things like that. And that's why in chamber divers, I even included the story of a high altitude research pioneer named Randy Lovelace. He built a breathing system in tested on himself by kind of stealing a plane a little bit and jumping out of it, obviously. So there's huge overlap here in the hostility of the environments that we're working in. And in the fact that the body is undergoing pressure differentials. So high altitude fighter pilots and astronauts all have to worry about decompression sickness. Because they're going from a higher pressure to a lower pressure. So our research has huge overlap there. They have to worry about their breathing systems. They have to worry about their carbon dioxide levels in the spaceship, which is now an enclosed environment, a lot like a hyperbaric chamber. And we actually hold our conferences together a lot of the times because the two environments, while wildly dissimilar in the pressures that we're facing, are united in the challenges.

[Terry Gross]

When you're doing research for the military, do you think about the lives that your research might be saving and the kind of mass casualties of the past that might happen again in the future? I mean, how focused are you on just analyzing the data and dealing with the research at hand? And how much are you thinking about the larger consequences of the kind of situations where your technology might be used or the results of your tests might be used?

[Rachel Lance]

Constantly. It's a constant concern for me. When I worked for the Navy, which was just short of nine years, I'll use this, an example. The government is not known for its lack of bureaucracy. So working for the government had this incredibly unique experience where I was in this big bureaucracy, and I would have to write memos for things that seemed ridiculous to me to justify, like, oh, why do you need stainless steel? It's more expensive. Well, if I don't buy that, it'll rust away in two days, things like that.

[Terry Gross]

It's underwater, right?

[Rachel Lance]

It's underwater. It's gonna rust. Exactly. So things like that were a regular obstacle there. And the reason that I love that job and engaged with that job so well, to the point that I wanted to keep researching for this community even after I left the Navy, was because I was able to interact with military personnel and I was able to see how much they wanted this so that it could improve their chances of coming home safely. I don't work on weapons systems. I work on safety standards and safety equipment, and I'm motivated by that daily.

[Terry Gross]

Well, thank you so much. This was so interesting. It's a pleasure having you on the show. Thank you so much.

[Rachel Lance]

Thank you so much for having me.

[David Biancooli]

Rachel Lance speaking to Terry Gross in 2024. Her book is called Chamber Divers the Untold Story of the D Day Scientists who Changed Special Operations Forces Forever.

[Various NPR Announcers]

SAM.

[David Biancooli]

Coming up, Justin Chang reviews Seurat, the new Spanish film he says is one of the best he's seen all year. This is Fresh air.

[Rachel Martin]

I'm Rachel Martin. If you're tired of small talk, check out the Wild Card podcast. I invite influential thinkers to open up about the big topics we all think about but rarely talk about. Tune in this fall to hear Mel Robbins, Malala Yousafzai and Brene Brown talk about everything from grief and God to ambition and forgiveness. Watch or listen on the NPR app, YouTube or wherever you get your podcast. There is so much happening in politics in any given week, you might need help putting it all in perspective as your week draws to a close. Join the NPR Politics podcast team for our weekly roundup. Here, our best political reporters zoom into the biggest stories of the week, not just what they mean, but what they mean for you all in under 30 minutes. Listen to the weekly roundup every Friday on the NPR Politics podcast.

[David Biancooli]

Our film critic Justin Chang says that Seurat is the best new movie he's seen this year. It's about a man searching for his lost daughter at a rave in the desert of southern Morocco. Seurat won a jury prize at the Cannes Film Festival this year and will represent Spain in the Oscar race for best International Feature. Here is Justin's review.

[Various NPR Announcers]

The Arabic word sirat means path or way. In Islamic scripture it refers to a narrow bridge that connects paradise and hell. That makes it a fitting title for the director Oliver Lache's new movie, which is both exhilarating and devastating. It's a survival story about several unlikely traveling companions making their way through a godforsaken stretch of the Sahara desert. It carries echoes of countless earlier films, from the arid landscapes of a John Ford Western to the post apocalyptic setting of Mad Max, but nothing about Sirat feels derivative or second hand. It's an astonishing piece of cinema. I haven't had a more gripping experience in a movie theater all year. It begins somewhere in southern Morocco, where hundreds of nomadic European revelers have gathered for a rave. It seems that World War three or something like it has broken out, though the specifics are left vague. Whatever's going on, Seurat initially plays like a party at the end of the world. Imagine a remake of the recent dystopian thriller Civil War set at Burning man and you'll have some idea. Lache sweeps you up in the intense physicality of the dancing and the propulsive beat of the music composed by the experimental electronic musician Kang Ding Ray. Wandering around this unruly desert bacchanal is a middle aged man named Luis, played by the Spanish actor Sergi Lopez. This clearly isn't Luis's scene. Along with his young son Esteban and their dog, Luis is searching for his 20something daughter, Mar, who vanished months ago and whom he has reason to suspect is among the ravers. But she's nowhere to be found and before long, armed officials show up and invoking a state of emergency, break up the party. Amid the ensuing chaos, five ravers drive off, bound for another rave further south. Luis and Esteban impulsively drive after them, hoping against hope that they'll find Mar. In Lache's previous films, including the 2016 drama Mimosas, which also chronicled a perilous journey through Morocco, he has worked mainly with non professional actors, with the exception of Sergi Lopez. That's also true here. The director recruited most of the principal cast from raves that he himself attended, and they're all naturals. I especially liked Stefaniagotta as a woman of few words but immense screen presence, and Jad Okide as a dancer of mesmerizing ability. You feel for these off the grid daredevils and you admire their survival tactics during what will prove to be an exceedingly dangerous trek. While the ravers have an enormous truck and a camper van, Luis and Esteban are in a small van that's ill equipped for the treacherous terrain. But the ravers, somewhat reluctantly at first, let them tag along. They all share their limited resources, including food, water and gas, and they help each other out when Luis has trouble fording a small river or when the truck gets stuck on a steep mountain road. Seurat is a visually and sonically overwhelming experience. It's full of majestic desert vistas and propelled by that thrillingly percussive score, it's also a drama of extraordinary tension and eventually shocking tragedy, in which death has a way of striking when you least expect it. I was often reminded of the Wages of Fear and Sorcerer, two classic nail biters, both adapted from a Georges Arnaud novel about a road trip from hell. What separates Seurat from those two films, though, is its lack of cynicism. Lopez is terrific as a father whose child has disappeared and who's understandably wary and mistrustful of the world. But even at his bleakest moments, Luis receives unexpected acts of compassion from his new companions. At one point, Esteban asks one of the ravers if he misses his family while traveling on the road, and the raver responds, I prefer this family. That might sound like something Vin Diesel would say in a Fast and Furious movie. And as it happens, Diesel's driving skills might have come in handy here. But Lache's film is as sincere in its tenderness as it is unrelenting in its ferocity. There's something powerful about the movie's belief that even as an apocalypse looms, kindness can survive and meaningful relationships can form. Just because the world is pitiless Seurat suggests, doesn't mean that people have to be.

[David Biancooli]

Justin Chang is a film critic at the New Yorker. He reviewed Seurat, now playing in select theaters on Monday's show, actress and singer Cynthia Erivo. She returns on screen as Elphaba in Wicked for Good, who claims her own power even as the world deems her the Wicked Witch. In Erivo's new memoir, Simply More, she explores similar themes, shedding other people's definitions of who she should be as a woman and an artist. I hope you can join us.

[Rachel Lance]

Something has changed within me Something is not the same I'm through with playing by the rules of someone else's game Too late for second guessing Too late to go back to sleep it's time to trust my instincts, close my eyes and leap it's time to try defying gravity. I think I tried defying gravity and you can't pull me down.

[David Biancooli]

To keep up with what's on the show and get highlights of our interviews, follow us on Instagram @NPRFreshAir and you can subscribe to our YouTube channel [e-mail] thisisfreshair. We're rolling out new videos with in studio guests, behind the scenes shorts and iconic interviews from the archive. Fresh Air's executive producer is Danny Miller. Sam Brigger is our managing producer. Our senior producer today is Roberta Shorrock. Our technical director and engineer is Audrey Bentham, with additional engineering support by Joyce Lieberman, Julian Hertzfeld and Deanna Martinez. Our interviews and reviews are produced and edited by Phyllis Meyer, Ann Marie Baldonado, Lauren Krenzel, Teresa Madden, Monique Nazareth, Thea Chaloner, Susan Yakundi and Anna Bauman. Our digital media producer is Molly Seavey. Nesper Hope Wilson is our consulting visual producer for Terry Gross and Tanya Moseley. I'm David Biancooli.

[Rachel Lance]

With a phone and an Internet connection, anyone can try to turn a creative passion into income.

[David Biancooli]

Creative work is more valuable than people realize.

[Various NPR Announcers]

It is going to be a hugely significant area of the economy.

[Rachel Lance]

But what does it mean to monetize all this creativity? TED Radio Hour's two part series explores the creator economy. Listen on the NPR app or wherever you get your podcasts. Mothers and Daughters, Daughters and Mothers.

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We explore the generational divide on our.

[Rachel Lance]

Latest episode of Books We've Loved About.

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Amy Tan's the Joy Luck Club with.

[Rachel Lance]

The indicators Whale and Wand.

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Find Books we've loved on NPR's Book.

[Rachel Lance]

Of the Day podcast feed on the NPR app or wherever you get your podcasts.

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You care about. What's happening in the world. Stay informed with NPR's State of the World podcast. In just a few minutes, we take you to stories around the globe. You might hear the latest developments in world conflicts or about what global events mean. For the price of your coffee, listen to the State of the World podcast from NPR.