A hyperbaric chamber delivers pure oxygen at pressures two to three times higher than normal atmospheric pressure, forcing significantly more oxygen into your blood and tissues than regular breathing can achieve. This extra oxygen accelerates healing, fights certain infections, and can reverse damage from conditions like carbon monoxide poisoning and decompression sickness. The therapy is FDA-approved for over a dozen medical conditions, though how it works goes well beyond simply “more oxygen.”
How Pressurized Oxygen Changes Your Body
Under normal conditions, your red blood cells carry nearly all the oxygen your body uses. They have a limit, though. Hemoglobin can only hold so much. A hyperbaric chamber gets around this bottleneck by dissolving extra oxygen directly into your blood plasma, the liquid portion of your blood that doesn’t rely on red blood cells at all. The higher the pressure, the more gas dissolves into the liquid. This is the same principle that keeps carbon dioxide dissolved in a sealed soda bottle: increase the pressure and more gas stays in solution.
At two to three times normal atmospheric pressure while breathing 100% oxygen, your plasma becomes saturated with oxygen that can reach tissues your red blood cells struggle to supply, particularly areas with damaged or blocked blood vessels. This is why the therapy is so effective for wounds that won’t heal on their own. The oxygen-rich plasma can seep into swollen, injured tissue where red blood cells physically can’t fit.
The elevated pressure also has a direct physical effect. Gas bubbles trapped in the bloodstream (from decompression sickness or air embolism) shrink as the pressure increases, which is why hyperbaric chambers were originally developed for divers. As the bubbles get smaller, oxygen gradually replaces the inert gas inside them, allowing the body to reabsorb them safely.
What It Triggers Beyond Oxygen Delivery
The chamber’s effects go deeper than just flooding tissues with oxygen. Repeated sessions stimulate your body to grow new blood vessels, a process called angiogenesis. Specialized stem cells are released from bone marrow and travel to damaged areas, where they help form new vasculature and repair tissue. Research has shown that this stem cell mobilization involves an enzyme that plays a key role in blood vessel health, triggering the release of cells that home in on oxygen-starved tissue.
There’s also a counterintuitive mechanism at work. Repeated exposure to high-oxygen environments causes your cells to build up antioxidant defenses. When you return to normal air between sessions, this antioxidant surplus tricks your cells into behaving as if oxygen levels are low, activating repair pathways that promote healing even when you’re no longer in the chamber. This is one reason treatments are given as a series rather than a single session.
FDA-Approved Uses
The FDA currently approves hyperbaric oxygen therapy for the following conditions:
- Decompression sickness (the bends)
- Air or gas embolism (gas bubbles in blood vessels)
- Carbon monoxide poisoning
- Gas gangrene (caused by Clostridium bacteria)
- Crush injuries
- Non-healing wounds, including diabetic foot ulcers
- Burns
- Radiation injuries
- Severe bone and skin infections
- Skin grafts and compromised flaps
- Severe anemia
- Sudden hearing loss
- Sudden vision loss
Wound healing is one of the most common applications. For diabetic foot ulcers, a systematic review found that hyperbaric therapy leads to lower amputation rates and faster wound closure compared to standard care. In one study, 78% of patients receiving the therapy achieved complete healing, while all patients in the control group required surgery. Another found that 33.3% of treated patients achieved full ulcer closure versus none in the control group. Not every trial shows dramatic results, but the overall pattern favors the therapy for stubborn wounds that resist conventional treatment.
What a Session Looks and Feels Like
There are two types of chambers. A monoplace chamber is a clear acrylic tube designed for one person. You lie down and slide inside, and the entire tube fills with pure oxygen. These are the most common in outpatient settings because they’re compact, relatively affordable, and don’t require staff inside the chamber.
A multiplace chamber is a room-sized unit that can hold several patients and a medical attendant at once. You breathe oxygen through a mask or hood while the room is pressurized with regular air. These are typically found in hospitals and are better suited for critically ill patients who need hands-on monitoring or IV medications during treatment.
A typical session lasts 90 to 120 minutes at pressures between 2.0 and 2.5 times normal atmosphere. During pressurization, you’ll feel fullness in your ears, similar to descending in an airplane. Swallowing or yawning usually relieves it. The number of sessions varies widely by condition. Diabetic foot ulcers typically require 30 to 40 daily sessions. Radiation injuries may need 30 to 60 treatments. Skin grafts generally require around 40 sessions total, split between wound bed preparation and post-surgical healing. Emergency conditions like gas gangrene start with three sessions in the first 24 hours, tapering over several days.
Side Effects and Risks
The most common side effect is ear discomfort. A large meta-analysis found that people receiving hyperbaric therapy were about 3.4 times more likely to experience ear pain than those receiving a placebo treatment. This ranges from mild pressure sensations to, in rare cases, middle ear barotrauma (minor injury to the eardrum from pressure changes). Sinus pain can also occur through the same mechanism.
Temporary vision changes are the second most frequent issue. Some people develop mild nearsightedness during a treatment course, which typically reverses within weeks after sessions end.
Oxygen toxicity is a rarer but more serious concern. At high pressures, oxygen itself can overstimulate the nervous system. Early warning signs include twitching around the mouth and in the hands, ringing in the ears, nausea, anxiety, and visual changes like tunnel vision. If these symptoms appear, treatment is paused immediately, which typically prevents progression to seizures. Modern protocols include scheduled “air breaks,” periods during a session where you breathe normal air instead of pure oxygen. This simple interruption reduces seizure risk by roughly tenfold.
Claustrophobia can be an issue in monoplace chambers, since you’re enclosed in a tube for up to two hours. Most facilities let you watch TV or listen to music, and the clear walls help, but it’s worth mentioning to your provider if enclosed spaces bother you.
Who Should Not Use a Hyperbaric Chamber
The only absolute contraindication is an untreated collapsed lung (pneumothorax). Changing the ambient pressure around someone with trapped air in their chest cavity can cause a life-threatening emergency as that air expands during depressurization. Anyone with a recent eye surgery involving gas injection should also avoid treatment, as the pressure changes can damage vision in the affected eye. Beyond these, your provider will evaluate individual risk factors like seizure history, certain medications, and lung conditions before clearing you for treatment.