What Is Hyperbaric Oxygen Therapy (HBOT)?

How hyperbaric oxygen therapy works

HBOT works by pushing more oxygen into your blood and tissues. Normally, red blood cells carry almost all the oxygen in your blood. Very little dissolves in the liquid part of the blood, the plasma. Under pressure, much more oxygen dissolves in the plasma. At about three times normal pressure, the oxygen dissolved in plasma alone can come close to what resting tissues need, according to a 2021 review in Medical Gas Research.

That extra oxygen has a few effects that matter for treatment:

• It shrinks gas bubbles. This is why HBOT treats decompression sickness and air bubbles in blood vessels (Mayo Clinic, 2024).
• It supports healing. Mayo lists the growth of new blood vessels and tissue and support for the immune system.
• It may reduce swelling and help stop infection. MedlinePlus (2024) says this can help some wounds, especially infected ones, heal faster.
• It clears carbon monoxide. High-pressure oxygen helps push carbon monoxide off the blood's oxygen carriers (Medical Gas Research, 2021).

The pressure matters. The Undersea and Hyperbaric Medical Society (UHMS), the main US professional body for hyperbaric medicine, defines HBOT as treatment in a hard-sided chamber at no less than 2.0 atmospheres absolute (ATA), breathing medical-grade oxygen, usually for 90 to 120 minutes (UHMS, Indications 15th edition). It says treatments backed by science are usually given at 1.9 to 3.0 ATA.

Types of hyperbaric chambers

There are two main kinds of medical chamber. A monoplace chamber is a clear tube for one person, filled with pressurized pure oxygen. A multiplace chamber is a room for two or more people. The room air is pressurized and each person breathes pure oxygen through a mask or hood. Mayo says the treatment effects are the same in both (Mayo Clinic, 2024).

Some wellness centers offer "mild" HBOT in soft, inflatable chambers. The UHMS defines mild HBOT as treatment below 1.5 ATA and calls it unproven. It notes that people in these chambers often breathe much less than 95% oxygen (UHMS). Mild and hard-shell HBOT are not the same treatment. Our mild vs hard-shell HBOT guide compares them.

What HBOT treats: FDA-cleared and UHMS-accepted uses

HBOT is an accepted treatment for about 15 conditions, from decompression sickness and carbon monoxide poisoning to radiation injury and some diabetic wounds. Three different lists decide whether a use counts as "approved", and they don't match exactly:

1. FDA clearance. The FDA regulates hyperbaric chambers as Class II medical devices and clears them through its 510(k) process (FDA, 2025). A chamber is cleared for specific uses, not for general health.
2. UHMS indications. The conditions where the UHMS says the evidence supports HBOT.
3. Medicare coverage. The conditions Medicare pays for under its national coverage rule, NCD 20.29 (current version effective 2017).

FDA-cleared uses

Harvard Health (2024) and Cleveland Clinic (2023) both summarize the FDA's list. Between them they name:

• air or gas bubbles in the blood vessels
• decompression sickness
• carbon monoxide poisoning
• gas gangrene and severe skin or bone infections
• crush injuries
• severe burns
• wounds that are hard to heal, such as diabetic foot ulcers
• radiation injury
• skin grafts and flaps at risk
• severe anemia when blood transfusions can't be used
• sudden hearing loss and sudden vision loss
• frostbite (Harvard)

UHMS indications and Medicare coverage

The UHMS's current list (15th edition) has 15 numbered indications. The table shows each one and whether Medicare's NCD 20.29 names it as covered.

Sources: UHMS; CMS NCD 20.29.

For diabetic wounds, Medicare covers HBOT only when you have type 1 or type 2 diabetes, the wound is Wagner grade III or higher, and you have already had an adequate course of standard wound care. Treatment stops being covered if the wound shows no measurable signs of healing in any 30-day period. Medicare also covers two conditions that aren't on the UHMS list: actinomycosis that hasn't responded to antibiotics, and acute peripheral arterial insufficiency (CMS NCD 20.29). Private plans set their own rules. See our HBOT insurance coverage guide.

Off-label and wellness uses: what the evidence says

"Off-label" here means a use the FDA has not cleared a chamber for. Some treatment centers claim HBOT treats Alzheimer's disease, autism, cancer and Lyme disease. The FDA has not cleared or approved HBOT for these conditions (Harvard Health, 2024). Cleveland Clinic adds depression, migraines and stroke to the unapproved list (Cleveland Clinic, 2023).

Some of these uses are being studied. Here is what the best-known studies found, and their limits.

Small trials like these are a reason for more research, not proof that HBOT works for these conditions. If you are thinking about HBOT for an off-label use, ask your doctor what the evidence shows for your situation. Insurance usually won't pay for it.

Benefits of hyperbaric oxygen therapy, by condition

HBOT's benefits depend on what it's treating. For some emergencies, Mayo calls it lifesaving: air bubbles in blood vessels, decompression sickness, carbon monoxide poisoning and serious crush injuries (Mayo Clinic, 2024). For other conditions, the evidence is real but more modest.

Diabetic foot ulcers

In a 2010 trial in Diabetes Care, 94 people with chronic diabetic foot ulcers got HBOT or a placebo (pressurized air) as an add-on to wound care. At one year, the ulcer had fully healed in 52% of the HBOT group and 29% of the placebo group. A 2015 Cochrane review of 12 trials found more ulcers healed with HBOT at six weeks, but not at one year. It found no clear difference in major amputations, and said flaws in the trials limit confidence in the results.

Radiation injury

Radiation for cancer can damage healthy tissue years later. In a 2008 trial in the International Journal of Radiation Oncology, Biology, Physics, 120 people with radiation damage to the rectum were evaluated. Those who got HBOT improved more than those who got a sham. A 2023 Cochrane review of 18 studies found that HBOT may improve late radiation injury to the head, neck, bladder and rectum, with low- to moderate-certainty evidence.

How long the benefits last

It depends on the condition. A bubble from decompression sickness may need only one long session (MedlinePlus, 2024). Wound results can fade: the Cochrane review above found the healing benefit at six weeks was not clear at one year.

Is HBOT safe?

HBOT is generally safe when given under medical supervision, and most side effects are mild and short-lived. But it has real risks, including ear injury, temporary vision changes, seizures from oxygen toxicity, lung collapse and fire (Mayo Clinic, 2024). Our HBOT side effects guide covers the risks and who shouldn't have it.

What a session is like

You lie in a clear tube or sit in a pressurized room for about 1½ to 2 hours while staff monitor you. Your ears may feel full as the pressure rises, as on a plane. See what to expect in an HBOT session.

How much HBOT costs and whether insurance pays

Prices vary a lot by setting and chamber type. Our HBOT cost guide has sourced figures. Medicare Part B may cover HBOT for the conditions in NCD 20.29, and you usually pay 20% of the Medicare-approved amount after the Part B deductible (Medicare.gov). Private coverage varies by plan. See does insurance cover HBOT.