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.
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.
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.
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)
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
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.