Hyperbaric Oxygen Chamber: What HBOT Can Do and What It Cannot Yet

In a hyperbaric chamber you lie or sit in an enclosed space where the pressure rises above normal atmosphere, and you breathe almost pure oxygen. Medicine has used this procedure, HBOT for short, for decades for diving accidents, poisonings and wounds that will not heal. In biohacking it became famous after Israeli studies in which sixty sessions lengthened telomeres in blood cells. It is a promising tool – and an often exaggerated one.

How HBOT works

Under normal conditions, haemoglobin in red blood cells is almost fully saturated with oxygen and cannot take up more. But when you breathe pure oxygen under a pressure of usually two to three atmospheres, oxygen starts to dissolve directly in the blood plasma, according to Henry's law – and in a many-fold larger amount. This way oxygen also reaches tissues with poor blood flow: swollen, infected or irradiated areas.

Besides the oxygen supply itself, HBOT has other effects. Pressure shrinks gas bubbles in the blood, high oxygen suppresses some bacteria, influences immune cells and supports the growth of new blood vessels. Also interesting is the so-called hyperoxic-hypoxic paradox: the body perceives repeated alternation between high and normal oxygen similarly to a lack of oxygen and triggers regenerative processes. The Israeli longevity protocols are built on it.

Approved medical indications

The 2016 European Consensus Conference on Hyperbaric Medicine graded indications by the strength of evidence and, for the first time, also named conditions in which HBOT does not help. A 2021 review lists 14 indications recognised by the American professional society. The best-supported include:

• Carbon monoxide poisoning – in a randomised NEJM trial, patients who had three HBOT sessions within 24 hours had memory and thinking problems after six weeks in 25% of cases, versus 46% with normal-pressure oxygen.
• Decompression sickness and air embolism – classic diving and hospital indications.
• Severe soft-tissue infections – such as gas gangrene or necrotising infections, as an add-on to surgery and antibiotics.
• Late radiation injury – to bone, bladder or bowel.
• Diabetic foot and some chronic wounds – as an add-on to standard care.
• Sudden hearing loss and retinal artery occlusion – the sooner, the better.

Outside these indications, use is experimental. This includes longevity, performance, post-COVID fatigue and concussion, where research is gaining pace but clear recommendations are still lacking.

The Israeli studies: telomeres and senescent cells

In 2020 the team of Shai Efrati from an Israeli hyperbaric medicine centre published two studies that went around the world. In the first, 35 healthy people aged 64 and over received 60 sessions over three months, five times a week. Each lasted 90 minutes at 2 atmospheres with 100% oxygen and five-minute air breaks every 20 minutes. Telomeres in several types of white blood cells lengthened by more than 20%, and the share of senescent, or "aged", helper T cells fell by 37%.

In the second, randomised study of 63 healthy older people, the same type of treatment improved attention, information-processing speed and blood flow in some brain areas compared with the control group.

The results are promising, but they need to be read soberly:

• The telomere study had no control group, and 30 people completed the protocol.
• Only blood cells were measured, not tissues. Telomere length in blood is not the same as the biological age of the whole body.
• Several authors work for a commercial company in hyperbaric medicine, which they disclosed in the study.
• Independent replication in larger groups and long-term results are still lacking.

Soft chambers versus medical ones

Medical chambers are rigid pressure vessels for one patient or several people at once. They operate at 2–3 atmospheres, the patient breathes almost pure oxygen through a mask or hood, and the session is run by trained staff under a doctor's supervision.

Soft, inflatable chambers, found in wellness centres or sold for home use, work at so-called mild hyperbaria, usually around 1.3 atmospheres. You breathe air or air enriched with oxygen from a concentrator, typically around 30%. According to the Australian and New Zealand Hyperbaric Medicine Group, such a session delivers roughly as much oxygen as breathing about 35% oxygen through a mask without any chamber at all. The group knows of no reliable evidence of therapeutic benefit from mild hyperbaria and does not recommend it for medical purposes.

In other words: the results of the Israeli studies concern medical chambers with 100% oxygen at 2 atmospheres and cannot be transferred to soft chambers.

Risks and who should be careful

When properly run, HBOT is among the safe medical procedures. Side effects do exist, however:

• Ear barotrauma – the most common problem. It occurs when you cannot equalise the pressure in the middle ear as pressure rises; pain or even eardrum damage can follow. The sinuses can be affected in a similar way.
• Claustrophobia – especially in narrow single-person chambers.
• Hyperbaric myopia – over longer series, distance vision may temporarily worsen; it usually returns to normal.
• Oxygen toxicity – a rare seizure during a session. The risk is raised by epilepsy, fever, low blood sugar, an overactive thyroid and certain medications.
• Untreated pneumothorax – the only absolute contraindication.
• Fire – a high oxygen concentration increases the risk of ignition. In 2025 the US FDA warned of reports of serious injuries and deaths with the use of hyperbaric devices.

If you have diabetes, be prepared for HBOT to lower your blood glucose. If you take medication, have heart or lung disease, or are pregnant, consult a doctor beforehand.

Where and at what cost

For approved indications, HBOT takes place in hospital-based hyperbaric centres, on a doctor's referral and usually covered by health insurance. Preventive and longevity protocols are offered by private clinics and wellness centres, and you pay for them yourself. The price of a single session varies widely by chamber type, pressure and country; a protocol of sixty sessions like the one used in the Israeli studies therefore means dozens of hours in the chamber and a considerable investment.

When choosing, ask what pressure the chamber reaches, whether you breathe 100% oxygen through a mask, who runs the session, whether a doctor is present and how the centre is prepared for emergencies. If the answer is "1.3 atmospheres and air from a concentrator", it is not the same treatment that was studied.