What is hyperbaric oxygen therapy?

Hyperbaric oxygen therapy, usually shortened to HBOT, means breathing concentrated oxygen while the pressure around you is higher than ordinary atmospheric pressure.

That definition matters because oxygen alone is not the whole treatment. The combination of oxygen and pressure changes how much oxygen can dissolve in the liquid portion of blood. It does not prove that HBOT will help every symptom or condition; it explains the mechanism being investigated.

What happens to oxygen under pressure?

At sea level, the air around us is at about 1 atmosphere absolute, written 1 ATA. Most oxygen in the blood is carried by haemoglobin inside red blood cells. A smaller amount is dissolved in plasma.

When the surrounding pressure and the partial pressure of oxygen rise, more oxygen dissolves in plasma. This follows a basic physical relationship known as Henry’s law. Researchers study whether that temporary increase can support tissue in particular clinical situations.

Mechanism is not the same as outcome. A plausible biological explanation can justify research, but only trials and clinical evidence can tell us whether patients actually benefit.

What is a session like?

At HBOT Medics, one person uses the chamber at a time. Pressure rises gradually. Your ears may feel full, much as they do during an aircraft descent, and the operator explains how to equalise them before the session begins.

At pressure, you breathe through the supplied oxygen system. You can communicate with the operator throughout, and a session can be stopped if necessary. Decompression is gradual.

Before entering, you follow the centre’s clothing and prohibited-item rules. They exist because oxygen-enriched environments require strict fire precautions.

See what the session feels like for the complete arrival-to-departure sequence.

Where is HBOT established?

Hyperbaric medicine has recognised uses including decompression illness and gas embolism. Other recognised indications depend on the clinical circumstances and specialist pathway. NHS availability and commissioning are narrower than the full range discussed in international hyperbaric guidance.

In England, NHS England’s specialised commissioning page lists decompression illness and gas embolism as the routinely commissioned indication. It lists carbon monoxide poisoning, diabetic foot ulcers, necrotising soft tissue infections, malignant otitis externa and radiation damage after pelvic radiotherapy as not routinely commissioned.

For many private-sector uses, such as general recovery, fatigue, cognition or athletic recovery, the evidence is not equivalent to the evidence for emergency diving medicine. Some areas have promising studies, some have conflicting results, and some have very little controlled evidence.

That is why this site separates condition guides. Each one states the strength and limits of its own evidence instead of treating one successful indication as proof for another.

What does the research say so far?

Three recent pieces of evidence show why a single verdict on HBOT is not possible.

A positive trial at 1.5 ATA. A 2025 double-blind, sham-controlled trial in Scientific Reports studied adults with symptoms that had persisted between six months and ten years after a brain injury. Participants received 40 sessions over 12 weeks at 1.5 ATA. The HBOT group’s symptom scores improved by 7.0 points more than the sham group’s (95% confidence interval 1.7 to 12.3). Only 47 people were analysed, so it is encouraging evidence rather than a settled answer. Our head injury evidence guide sets out the detail.

A negative trial for long COVID. The HOT-LoCO trial randomised 80 people with long COVID to ten sessions of oxygen at 2.4 bar or a sham procedure over six weeks. Both groups improved, with no significant difference between them at 13 weeks. We explain what that result can and cannot tell you in our HOT-LoCO summary.

Mixed evidence after radiotherapy. A 2023 Cochrane review of 18 studies and 1,071 participants found HBOT may improve some late radiation tissue injuries of the head and neck, bladder and lower bowel. Certainty was mostly low, studies were small, and the best timing and dose remain unclear.

Together, these show the pattern that runs through the whole field: results depend on the condition, the pressure, the number of sessions and the comparison group.

Is HBOT safe?

HBOT is generally well tolerated when screening and chamber rules are followed, but it is not free of risk. The same Cochrane review reported temporary reductions in visual sharpness and ear barotrauma as the main adverse effects. Pressure in the ears and sinuses is the sensation most people notice, and the operator can slow or pause pressurisation if equalising is difficult.

Some people should not enter a chamber, or need medical advice first. Our guide to who HBOT is not for lists the main exclusions and cautions, and the course declaration exists to catch them before session one.

Pressure and protocol matter

Study results cannot automatically be transferred between chambers or protocols. Pressure, oxygen delivery, session duration, number of sessions and the people enrolled can all differ.

Our chamber operates at 1.5 ATA. Where a study used a different pressure or a much longer course, the relevant evidence guide should say so. The chamber’s oxygen-percentage publication remains subject to equipment verification, so this article does not substitute an inferred number for a measured one. The chamber specification page records what has been verified.

Can you book directly?

Yes. New and returning adults can book routine HBOT with no GP referral needed. Medical consultation included with every Course.

One consent and medical declaration covers the course and is associated with session one. It is sent around 24 hours before that appointment. Reception handles routine consent and risk agreement; only flagged answers need clinical review. Every Course includes a doctor consultation at no additional cost; it is not a booking gate and does not delay session one.

Direct booking does not mean screening is optional. It means screening happens through the declared course process rather than forcing every patient through a consultation gate.

The useful short answer

HBOT is oxygen plus pressure. The pressure increases dissolved oxygen temporarily; whether that produces a meaningful benefit depends on the indication and protocol. Ask three questions before paying: what pressure is used, what evidence applies to your goal, and what screening protects you if HBOT is unsuitable.