What is Hyperbaric Oxygen Therapy? | Green Oxygen Hyperbarics

Chapter One 01

Where it came from

HBOT is not a new idea. It travelled three and a half centuries: from a 17th-century Irish physician with a bellows-powered room, through the laboratories and dive lockers that turned a hunch into a science, to the soft-shell studio in Marlow.

Illustration of physician Nathaniel Henshaw beside a cutaway diagram of his 1662 domicilium - a sealed chamber whose internal air pressure could be raised or lowered with an organ-bellows

Artist's impression · Henshaw's domicilium, 1662

Act One · The 17th century

1662

Nathaniel Henshaw · The Domicilium

The first chamber.

Long before anyone could explain why, an Irish physician named Nathaniel Henshaw built the world's first pressurised therapeutic room. He called it the domicilium: a sealed chamber whose internal air could be compressed or thinned with a set of organ-bellows. Henshaw was convinced that altering the density of the air around a person could ease everything from lung complaints to low spirits.

He had no way to prove it. The physics that would justify the idea barely existed. Robert Boyle published the first relevant gas law that very same year, and William Henry's law of solubility was still 140 years away (both are explained in Chapter Two). What Henshaw got right was the principle the whole field still runs on: put the air under pressure, and something measurable happens to the body breathing it.

Paul Bert, French physiologist (1833-1886), author of La Pression Barométrique - the foundational text on hyperbaric physiology

Portrait of Paul Bert · Wikimedia Commons

Act Two · The 19th century

1878

Paul Bert · Paris

The year it became a science.

By the 1800s, pressurised "pneumatic institutes" had sprung up across Europe, selling vague restorative cures to the Victorian middle classes. Most were closer to spectacle than medicine, until the French physiologist Paul Bert sat down and did the work.

His 1878 masterwork, La Pression Barométrique, ran past 1,100 pages and set out, for the first time, the real physiology of altered pressure: how the body takes up oxygen and nitrogen under load, where the dangers of oxygen toxicity begin, and how gases pass between blood and tissue. The fashionable institutes faded within a generation. Bert's physiology became the foundation every modern chamber is still built on. The acute spike of oxygen toxicity is named the "Paul Bert effect" to this day.

United States Navy sailors inside a decompression chamber - the modern recompression chamber owes its standardisation to the US Navy

US Navy photo · Naval Base Guam dive locker · Wikimedia Commons

Act Three · Mid 20th century

1937

US Navy · Dive Medicine

The year it was standardised.

The discipline grew up inside the military. As deep-sea diving became routine, so did decompression sickness, or "the bends," caused by nitrogen bubbling out of a diver's blood on a too-fast ascent. In 1937 the US Navy's medical division formalised the fix: re-pressurise the diver and feed them oxygen, forcing the nitrogen back into solution so the body can shed it slowly and safely.

The Navy's published treatment tables and recompression protocols became the global standard, copied by navies and hospitals everywhere. Nearly a century on, decompression sickness remains the most rigorously evidenced, universally accepted use of hyperbaric oxygen there is: the bedrock the whole field stands on.

Archival photograph of the courtyard of the Wilhelmina Gasthuis hospital complex in Amsterdam - the hospital where Ite Boerema built his hyperbaric operating chamber

Wilhelmina Gasthuis, Amsterdam (Boerema's hospital) · Rijksmuseum / Wikimedia Commons

Act Four · Post-war clinical

1956

Ite Boerema · Amsterdam

The year medicine caught up.

If the Navy made it safe, a Dutch surgeon made it medicine. At the University of Amsterdam's Wilhelmina Gasthuis hospital, the surgeon Ite Boerema began operating inside a giant pressurised steel chamber, flooding patients with oxygen to buy precious minutes during open-heart surgery on children with congenital defects. His famous paper, "Life without blood," showed an animal could survive on dissolved plasma oxygen alone.

Boerema is now regarded as the father of modern hyperbaric medicine. From his theatre the practice spread worldwide for the short, evidence-rich list of conditions hospitals still treat with it today: carbon-monoxide poisoning, problem wounds, radiation injury and serious infection. It was hard-shelled, staffed and expensive, but unmistakably real.

The Green Oxygen Oxydise soft-shell hyperbaric chamber in the Marlow studio, lit in calm purple - modern low-pressure HBOT

Modern soft-shell chamber · Green Oxygen, Marlow

Act Five · The present day

1990s to now

Soft-shell · 1.5 ATA · Wellness

The years it became everyday.

For three centuries the chamber lived in a hospital or a dive locker. Then, through the 1990s and 2000s, soft-shell, low-pressure chambers arrived: roomy, comfortable, gentle to pressurise at 1.3-1.5 ATA, and, crucially, usable outside a clinic. The physics hadn't changed a word since Boyle, Henry and Bert. Only the access had.

Elite athletes took it up for recovery. The longevity world took it up for the slow, compounding cellular effects. And calm studios like ours in Marlow took it up as something you can simply build into an ordinary week: a repeatable habit rather than an emergency. That's the chapter we're living in, and it's why you're reading this.

Chapter Two 02

How it works

A calm room, a great deal more oxygen, and two old gas laws that explain almost everything. You met their discoverers a moment ago. Here is what their equations actually do.

The Green Oxygen Oxydise soft-shell hyperbaric chamber beneath the studio window in Marlow - where a 60-minute HBOT session takes place

Soft-shell chamber · Green Oxygen, Marlow

The Basics · What it is

1.5 ATA

96% Oxygen · 60 minutes

A calm room, and a great deal more oxygen.

Stripped of the history, HBOT is simple to describe. You lie down inside a chamber; over about five minutes it pressurises to 1.5 ATA, roughly the pressure you'd feel five metres underwater, while you breathe oxygen at close to 96%, nearly five times the 21% in ordinary air. You spend an hour reading or dozing; five minutes to depressurise, and you climb out. Most people find it deeply relaxing.

The interesting part is invisible. The combination of more pressure and more oxygen drives far more O₂ into your blood and tissues than ordinary breathing ever could. Exactly how much, and why, comes down to two gas laws, and the two men you just met in Chapter One.

The Shannon Portrait of the Honourable Robert Boyle (1627-1691), the natural philosopher whose 1662 gas law underpins hyperbaric science

Shannon Portrait of Robert Boyle · J. Kerseboom, 1689 · Wikimedia Commons

The First Law · 1662

Robert Boyle · Boyle's Law

Squeeze a gas, and it shrinks.

Boyle's LawP × V = constant

Robert Boyle, a founder of the Royal Society and of modern chemistry, showed that at a fixed temperature, the pressure and volume of a gas are inversely linked: push the pressure up and the volume falls in exact proportion. That is what P × V = constant means. Double the pressure, halve the volume.

You feel Boyle's Law every time the chamber pressurises. The air in your ears and sinuses is being compressed, which is why you equalise just as you would on a plane or a dive. It's also why a gas bubble trapped in a diver's blood physically shrinks under pressure: the very effect the Navy exploits to treat the bends. Boyle gave Henshaw's chamber its first hard rule. But pressure alone doesn't get oxygen into you. For that, you need the second law.

William Henry, English chemist (1774-1836), author of Henry's Law on the solubility of gases in liquids

Engraving of William Henry · Wikimedia Commons

The Second Law · 1803

William Henry · Henry's Law

Pressure dissolves gas into liquid.

Henry's LawC = k × P

A century and a half later, the Manchester chemist William Henry found the law that does the real work. The amount of a gas that dissolves into a liquid is directly proportional to the pressure of that gas above it: C = k × P. Raise the pressure of the oxygen you're breathing, and more of it dissolves straight into the watery plasma of your blood.

This matters because of where that oxygen can go. Normally almost all the oxygen in your blood rides on haemoglobin inside red blood cells, which at sea level is already full. But oxygen dissolved freely in plasma has no such ceiling: under Henry's Law it rises in direct proportion to pressure, and plasma carries it into swollen, inflamed or poorly-circulated tissue that red cells struggle to reach. That is the whole trick of HBOT, in a single equation.

Partial pressure of oxygen reaching your lungs

Normal air
21% O₂ · 1 atm

0.21 atm

In our chamber
~96% O₂ · 1.5 atm

≈ 1.44 atm · ~7× more

Put Boyle and Henry together and the arithmetic is simple. In normal air, the oxygen reaching your lungs sits at about 0.21 atm. Inside the chamber, at 96% oxygen and 1.5 atmospheres, it jumps to roughly 1.44 atm, nearly seven times higher. By Henry's Law, that is how much more oxygen dissolves into your plasma with every breath.

Why this is the part that matters: at sea level your haemoglobin is essentially full, so you can't load more oxygen on just by breathing harder. The oxygen dissolved freely in plasma is the one number that can rise, and Henry's Law says it rises in direct proportion to pressure. Under HBOT that dissolved fraction increases enormously, reaching tissues red blood cells struggle to supply: the swollen, the inflamed, the poorly-circulated, the places that often need oxygen the most.

Chapter Three 03

What the oxygen does

From a single breath to a cascade of cellular responses: the well-documented mechanisms underneath, and the everyday differences people actually feel.

Futuristic visualisation of a human body with its vessels, organs and nervous system lit up - representing how dissolved oxygen reaches every compartment of the body

Visualisation · the whole-body cascade

In Your Body · The cascade

From a breath to a cell

One breath, a whole-body response.

Once that surplus oxygen is dissolved in your plasma, it doesn't stay put. It diffuses out of the bloodstream into the tissues, the interstitial fluid, the cerebrospinal fluid and the lymph, every wet compartment of the body, and from there into the cells themselves.

At the cellular level, raised oxygen tension turns several "knobs" at once. Some respond during the session; others over the hours and days afterward, as the body adapts to a stimulus it has learned to expect. This is why HBOT rewards a protocol rather than a single visit: the adaptations compound. What follows are the main mechanisms by which higher tissue oxygen is understood to influence the body. None is a claim to treat a condition; it's a description of what oxygen does to cells.

Mitochondrial energy production

Your mitochondria are the cellular power plants that generate ATP, the energy currency of every process in your body. They run on oxygen via oxidative phosphorylation. Increasing the oxygen available to them directly supports more efficient ATP production. Tired tissues, stressed cells and recovering muscles all benefit from cellular energy being more abundant.

Inflammation regulation

HBOT is widely studied for its modulating effect on inflammation. Research suggests it can shift the balance of pro- and anti-inflammatory signalling molecules, and dampen certain immune-cell pathways that drive chronic inflammation. It's one of the main reasons guests dealing with long-term tightness, joint discomfort or post-exercise soreness report relief over a run of sessions.

Stem cell mobilisation

Research on hyperbaric oxygen has explored its role in mobilising stem cells from bone marrow, releasing them into the bloodstream where they can travel to areas needing repair. This is one of the more quietly exciting frontiers of HBOT research; multiple studies have observed measurable increases in circulating progenitor cells following hyperbaric exposure.

Angiogenesis: new blood vessels

High tissue oxygen tension stimulates vascular endothelial growth factor (VEGF), the signalling protein that drives angiogenesis, the formation of new capillaries and microvessels. Over a series of sessions, this can improve circulation in tissues that previously had poor blood supply, improving their long-term oxygenation even outside the chamber.

Hypoxia-inducible signalling

Paradoxically, intermittent hyperoxia (high oxygen during the session) followed by return to normal pressure appears to upregulate hypoxia-inducible factors (HIFs), the master switches cells use to respond to low-oxygen stress. This "hyperoxic-hypoxic paradox" triggers many of the same adaptations as altitude training, without the downside. An active area of HBOT research.

Fibroblast & collagen activity

Oxygen is essential for fibroblast function, the cells that build and maintain connective tissue and lay down collagen during wound healing. Hyperbaric oxygen supports fibroblast activity, which is why HBOT has a long history of clinical use in wound healing and is also explored in cosmetic and aesthetic contexts.

Antibacterial effect

Many problematic bacteria are anaerobic: they thrive in low-oxygen environments. Saturating tissue with oxygen is inhospitable to them and can enhance the activity of certain neutrophils (your body's bacterial first responders). One of the most established clinical effects of HBOT, and the basis of its long history in wound and infection care.

Neuroplasticity & cognition

Your brain consumes around 20% of all the oxygen you breathe, despite being 2% of your body weight. More available oxygen supports the metabolic processes underlying neuroplasticity, the brain's ability to rewire and form new connections. HBOT's effect on focus and mental clarity is one of the most consistently reported guest experiences and an area of substantial ongoing research.

Reactive oxygen signalling

Briefly elevated oxygen produces a small, controlled rise in reactive oxygen species (ROS). Far from harmful, controlled ROS act as signalling molecules that trigger your cells' own antioxidant and repair defences, a phenomenon called hormesis ("what doesn't kill you makes you stronger", at the cellular level). Done right, HBOT exploits this hormetic effect.

Oedema & swelling

Hyperbaric pressure causes peripheral vasoconstriction (narrowing of blood vessels) while still increasing overall tissue oxygen delivery, a useful combination for reducing swelling without starving tissues of oxygen. One of the long-standing clinical observations of HBOT in trauma and acute-injury contexts.

Mitochondrial biogenesis

Beyond helping existing mitochondria work more efficiently, intermittent hyperbaric oxygen is studied for encouraging mitochondrial biogenesis, prompting cells to build entirely new mitochondria. More mitochondria mean more capacity to produce energy, a change that accrues over a full protocol rather than in any single one.

Telomeres & cellular ageing

One of the most talked-about findings in recent HBOT research: a widely-discussed 2020 study reported that a structured run of sessions was associated with longer telomeres, the protective caps on your chromosomes that naturally shorten with age, alongside a drop in senescent "worn-out" cells. Early, and still being explored, but a key reason the longevity world pays close attention.

Chapter Four 04

Who uses it now, and what for

From dive lockers to locker rooms to living rooms. The chamber escaped the hospital and the Navy: here's who reaches for it now, and what they're really after.

A muscular athlete - representative of the elite sportspeople who use hyperbaric oxygen for recovery between hard efforts

Elite sport · Recovery

Locker rooms

Where it started

The athletes got there first.

Hyperbaric recovery has been widely reported across elite sport, with Premier League football, the NFL and NBA, UFC fight camps and Olympic swimming among them, where shaving hours off recovery between efforts is worth a great deal. What began in a Navy dive locker became a fixture of the high-performance world.

The appeal is simple: for one hour the body is handed the conditions it likes best for repair: abundant oxygen, no demands, complete rest. People in and out of sport use it between hard efforts to bounce back feeling more like themselves, sooner. It is an hour banked against the next big effort.

A glowing human figure standing before a green-and-purple DNA double helix - representing the longevity and biohacking movement's interest in hyperbaric oxygen for cellular health

The longevity world · Ageing well

The longevity movement

From fringe to front page

The longevity crowd's standing habit.

Human-biology and longevity voices, with Gary Brecka prominent among them, have put HBOT in front of millions, framing it as a tool for cellular energy, skin and "healthspan". Biohacking podcasts and longevity clinics helped move the chamber out of the hospital and into the wellness conversation.

It's the crowd that treats the chamber like a standing gym habit for your cells: not a quick fix, but a repeated, gentle practice measured in months and years. Oxygen feeds the fibroblasts that keep skin firm and bright, which is why the same circles fold it into how they age well, from the inside out.

A vivid brain scan visualisation - representing the focus and clarity that founders and high performers seek from HBOT

Founders & high performers · Focus

Founders & high performers

An hour that buys an edge

Focus, with a payoff.

Founders, executives and creatives have adopted it for the same reason they guard their training time: one hour that pays back in how they feel, focus and perform. In a culture obsessed with optimisation, a chamber you can't check your phone in is its own kind of luxury.

The brain is the body's hungriest organ for oxygen: barely 2% of your weight, a fifth of every breath. Guests chasing sharper focus and quicker thinking make it a standing habit; "Head feels so clear" is among the most common things we hear the morning after.

A runner striding out on an athletics track in the sunshine - representing the everyday active people who now build hyperbaric oxygen into an ordinary week

Marlow, today · Everyday wellness

Marlow, today

And now, everyone.

The real shift is access. Soft-shell, low-pressure HBOT brought the same physics to a calm local studio. The people who once flew somewhere for this now have it down the road, which is rather the point of what we built.

For most, it's the everyday things: staying ahead of the stiff, slow-to-settle aches that creep in with age and training, moving more freely, recovering faster from a hard week, feeling steadier through the day. It is not a cure for anything. It is a quiet, repeatable habit that leaves people feeling more like themselves.

What is HyperbaricOxygen Therapy?