HBOT guide and glossary

What is HBOT?

HBOT is a medical treatment in which you breathe pure oxygen inside a chamber at higher-than-normal air pressure. This increases the oxygen carried in your blood and delivered to tissues. A clinician determines whether it is appropriate for your condition. How HBOT works.

What is it used for?

Established uses include decompression sickness, carbon monoxide poisoning, selected hard-to-heal diabetic wounds, delayed radiation injury, certain serious infections, and skin grafts or flaps with a threatened blood supply. It is often one part of a broader treatment plan. Eligibility depends on the specific diagnosis and clinical circumstances; not every wound or infection requires HBOT. See the UHMS list of indications.

Explore clinic listings for wound care and radiation injury.

What happens during a session?

You sit or lie in the chamber while the pressure rises gradually, breathe oxygen during treatment, then return gradually to normal pressure. Your ears may feel pressure similar to an airplane flight. Some chambers hold one person; larger chambers accommodate several people using oxygen masks or hoods. Session length and the number of visits depend on the treatment plan. What to expect during HBOT.

Understanding chamber types

Hard-shell and soft-shell describe construction: rigid walls or flexible, inflatable walls. Monoplace and multiplace describe capacity: one person or several. Pressure and oxygen delivery are separate details. Lower-pressure “mild hyperbaric” services are not interchangeable with clinical HBOT; evidence for one protocol does not establish benefits for another. Ask the clinic which setup and medical supervision it provides. UHMS definitions and treatment standards.

Risks and safety

Possible effects include ear or sinus pressure injuries, temporary vision changes and discomfort in enclosed spaces. Less common complications include lung injury and oxygen-related seizures. Oxygen-rich environments also require strict fire-safety precautions. Tell the clinician about your medical history and medications, and ask how the facility screens and monitors patients. Risks and precautions; FDA safety guidance.

What does recent research say?

Results depend on the condition and the treatment protocol. Recent studies show both promising findings and important limits:

Wound healing: A 2026 trial of 80 people with chronic venous leg ulcers found better short-term healing when HBOT was added to standard care. It was a single-center study without a sham treatment, so the authors called for stronger trials before routine use.
Long COVID: A 2022 trial of 73 people reported cognitive and symptom improvements after 40 sessions. A 2025 placebo-controlled trial of 101 people testing different oxygen and pressure regimens over 10 sessions found no significant treatment differences. The different protocols and populations make direct comparisons difficult.

A positive study for one condition does not establish benefits for every use advertised by a clinic. Ask which evidence supports the specific treatment being proposed for you.

Selected research checked September 19, 2026. This is an introduction, not a comprehensive evidence review or personal medical advice.

Glossary

Adjunctive treatment: A treatment used alongside other care. HBOT may form part of a wider treatment plan.
ATA (atmospheres absolute): A measure of total pressure. 1 ATA is normal atmospheric pressure at sea level; 2 ATA is twice that pressure.
Hard-shell chamber: A chamber with rigid walls, usually metal or acrylic. It may hold one person or several. The shell alone does not tell you the treatment pressure or oxygen concentration.
HBOT: Hyperbaric oxygen therapy: breathing oxygen in a chamber at increased pressure.
Mild hyperbaric (mHBOT): A term used for lower-pressure hyperbaric services. Ask about the actual pressure and oxygen delivery; protocols are not interchangeable.
Monoplace chamber: A chamber designed for one person.
Multiplace chamber: A chamber that accommodates several people, who breathe oxygen through masks or hoods.
Oxygen concentration: The percentage of oxygen in the gas you breathe. This is separate from chamber pressure: 2 ATA does not mean 100% oxygen.
Sham-controlled trial: A study that compares treatment with a simulated treatment, helping researchers distinguish treatment effects from expectations and other influences.
Soft-shell chamber: A flexible, inflatable chamber, commonly used for lower-pressure services marketed as mild hyperbaric. Its pressure and oxygen delivery differ from conventional medical HBOT.
Treatment protocol: The details of a treatment plan, including pressure, oxygen delivery, session length and number of sessions.
UHMS: The Undersea and Hyperbaric Medical Society, a professional organization that publishes HBOT guidance and accredits hyperbaric facilities.

Understanding HBOT

More guides