A hyperbaric chamber is a sealed, pressurized enclosure that allows a person to breathe pure oxygen at air pressure levels two to three times higher than normal atmospheric pressure. This forces significantly more oxygen into the bloodstream than regular breathing can deliver. At sea level, dissolved oxygen in blood plasma sits around 0.3 mL per deciliter. Inside a hyperbaric chamber pressurized to three atmospheres, that number jumps to 6 mL per deciliter, a twentyfold increase that drives oxygen deep into damaged or oxygen-starved tissues.
How Pressurized Oxygen Works in the Body
The physics behind a hyperbaric chamber follow a simple principle: the higher the pressure surrounding a gas, the more of that gas dissolves into a liquid. Your blood is mostly water, and under normal conditions it can only carry so much dissolved oxygen. Raise the pressure inside a sealed chamber and oxygen molecules pack into your blood plasma far more densely than your lungs could manage on their own.
That extra oxygen triggers several biological responses. It stimulates the growth of new blood vessels in wounded tissue by activating signaling proteins that tell cells to multiply and migrate. In diabetic wounds specifically, high-pressure oxygen promotes the proliferation of fibroblasts (the cells that build connective tissue) and encourages the blood vessel lining cells to form new capillaries. The elevated oxygen also causes blood vessels to constrict slightly, which reduces swelling in injured areas without cutting off oxygen supply, since the plasma is already carrying so much dissolved oxygen that the narrower vessels still deliver more than usual.
Types of Hyperbaric Chambers
There are three main designs, and they differ in important ways.
Monoplace chambers hold one person at a time. They’re typically made of clear acrylic so you can see out, and the entire tube fills with 100% oxygen. You simply breathe normally without wearing a mask or hood. These chambers can reach pressures up to 3.0 atmospheres, which is the range used for most medical treatments.
Multiplace chambers are room-sized units that treat several patients simultaneously. The whole room is pressurized with regular air, and each patient wears a hood or mask that delivers pure oxygen. These chambers allow medical staff to enter alongside patients, which is useful for people who need monitoring or hands-on care during treatment.
Soft or portable chambers are inflatable units sometimes marketed for home use. They max out at 1.3 atmospheres, well below the pressures used in clinical settings. The limited pressure means they deliver far less dissolved oxygen than medical-grade chambers.
What Conditions It Treats
Hyperbaric oxygen therapy has a relatively narrow set of approved medical uses, all situations where tissues are critically short on oxygen or where pressure itself solves a physical problem.
Decompression sickness is the classic example. When a scuba diver ascends too quickly, dissolved nitrogen in the blood forms bubbles that can block blood flow and damage tissue. Placing the diver back under high pressure inside a hyperbaric chamber shrinks those bubbles. The pressure is then lowered gradually, with designated pauses, giving the excess nitrogen time to leave the body safely through normal breathing.
Carbon monoxide poisoning is another well-established use. Carbon monoxide binds to red blood cells roughly 200 times more tightly than oxygen does, so breathing normal air isn’t enough to displace it quickly. The extreme oxygen concentration inside a hyperbaric chamber speeds up the process dramatically.
Other covered conditions include:
- Diabetic wounds of the lower extremities that haven’t healed after at least 30 days of standard wound care
- Radiation injury to bone or soft tissue (a delayed side effect of cancer treatment)
- Necrotizing fasciitis and gas gangrene, aggressive infections that destroy tissue
- Chronic bone infections that haven’t responded to antibiotics or surgery
- Crush injuries and reattachment of severed limbs
- Compromised skin grafts
- Cyanide poisoning
For diabetic wounds, Medicare and most insurers require that the wound be classified as severe (Wagner grade III or higher), that standard wound care has been tried for at least 30 consecutive days with no measurable healing, and that hyperbaric therapy is used alongside continued standard care rather than as a replacement. Wounds must be re-evaluated every 30 days, and coverage stops if there’s no progress within any 30-day treatment window.
What a Session Feels Like
A typical session lasts 90 minutes to two hours. In a monoplace chamber, you lie down on a padded table that slides into the tube. As pressure builds during the first several minutes, you’ll feel fullness in your ears, similar to the sensation of descending in an airplane. Swallowing, yawning, or gently blowing against a pinched nose usually relieves this. Once the chamber reaches treatment pressure, most people simply rest, watch a screen, or sleep. At the end of the session, pressure is gradually lowered back to normal.
Treatment plans vary widely depending on the condition. Some emergencies like carbon monoxide poisoning may need only a few sessions. Chronic wounds or radiation injuries often require 20 to 40 sessions, typically scheduled five days a week.
Risks and Side Effects
Middle ear barotrauma is the most common side effect. In a study tracking nearly 6,000 patients over eight years, ear injuries occurred in about 9.2% of all treatments. The large majority of these were minor, with roughly 69% showing only minimal changes on examination. About 1.5% of all patients in that study had to stop therapy because of ear problems. People who already have difficulty equalizing ear pressure are at higher risk, with a 20.3% incidence in that group.
Oxygen toxicity is a rarer but more serious concern. Breathing pure oxygen at high pressure for extended periods can, in rare cases, trigger seizures. People with seizure disorders face elevated risk. Sinus pain can also occur, particularly in people with upper respiratory infections or chronic sinusitis, since congestion makes it difficult to equalize pressure in the sinus cavities.
The only absolute reason someone cannot enter a hyperbaric chamber is an untreated collapsed lung (pneumothorax). As the chamber depressurizes at the end of a session, trapped air in the chest cavity would expand and could create a life-threatening emergency. People with severe emphysema face a similar risk if air-filled pockets in their lungs could rupture during decompression. Certain chemotherapy drugs also interact badly with hyperbaric oxygen, so treatment timing needs to account for drug clearance.
Cost and Insurance Coverage
Medicare covers hyperbaric oxygen therapy for its list of approved conditions when treatment is administered in a proper chamber, whether monoplace or multiplace. Private insurers generally follow similar guidelines, though specific requirements vary by plan. For diabetic wounds, the approval process is particularly structured: you need documented evidence that standard wound care failed over at least 30 days, and your medical team must show measurable improvement every 30 days to continue coverage.
Out-of-pocket costs for patients without coverage or those seeking treatment for non-approved conditions can range from $200 to $400 or more per session, making a full course of 30 or 40 sessions a significant expense. Clinics offering hyperbaric therapy for conditions outside the approved list, such as anti-aging, athletic recovery, or cognitive enhancement, are not covered by insurance, and the evidence supporting those uses remains limited.