Hyperbaric oxygen therapy (HBOT) is a specialist medical treatment in which patients breathe 100% pure oxygen inside a pressurised chamber, significantly increasing oxygen delivery to tissues throughout the body. Note that the term 'hyper bariatric oxygen therapy' does not correspond to a recognised clinical term — 'hyperbaric' relates to elevated pressure, whilst 'bariatric' concerns obesity treatment. This article covers HBOT as a standalone, evidence-based intervention: how it works, its approved uses under NHS and NICE guidance, what patients can expect during treatment, associated risks and contraindications, and how to access it on the NHS or privately in the UK.

What Is Hyperbaric Oxygen Therapy and How Does It Work?

HBOT involves breathing 100% oxygen in a pressurised chamber (1.5–3.0 ATA), dissolving oxygen directly into blood plasma via Henry's Law to increase tissue oxygen delivery. Note: 'hyper bariatric oxygen therapy' is not a recognised clinical term.

Hyperbaric oxygen therapy (HBOT) is a medical treatment in which a patient breathes 100% pure oxygen inside a pressurised chamber, typically at pressures between 1.5 and 3.0 atmospheres absolute (ATA). Under these conditions, oxygen dissolves directly into the blood plasma — not just into haemoglobin, which is already near-saturated when breathing room air — significantly increasing the total amount of oxygen delivered to tissues throughout the body.

The underlying mechanism relies on Henry's Law, which states that the amount of gas dissolved in a liquid is proportional to the pressure applied. By raising both the concentration of oxygen and the ambient pressure, HBOT can deliver oxygen to areas with compromised circulation or damaged tissue that would otherwise receive insufficient supply. Typical treatment tables vary by indication — for example, 2.0–2.5 ATA for 60–90 minutes is commonly used for wound-related indications — and are determined by the prescribing hyperbaric physician.

Several biological mechanisms have been proposed or observed in research settings, though the strength of clinical evidence varies by indication:

• Angiogenesis — stimulating the formation of new blood vessels

• Antimicrobial activity — inhibiting the growth of anaerobic bacteria

• Reduction of inflammation — modulating cytokine release and oedema

• Enhanced wound healing — promoting collagen synthesis and fibroblast activity

These mechanisms are supported by guidance from the Undersea and Hyperbaric Medical Society (UHMS) and the European Committee for Hyperbaric Medicine (ECHM), and are referenced in British Hyperbaric Association (BHA) patient resources. It is important to note that not all proposed mechanisms translate into proven clinical benefit across every condition for which HBOT is used.

It is also worth noting that the term 'hyper bariatric oxygen therapy' does not correspond to a recognised clinical term. 'Hyperbaric' refers to elevated pressure, whilst 'bariatric' relates to the treatment of obesity. There is no established link between the two terms in medical literature or regulatory guidance. This article addresses hyperbaric oxygen therapy (HBOT) as a standalone, evidence-based medical intervention, which is the most clinically relevant interpretation of the search term.

Approved Medical Uses and NICE Guidance in the UK

NHS England routinely commissions HBOT for decompression sickness and arterial gas embolism; other indications, including diabetic foot ulcers, require an IFR or research pathway, and NICE NG19 advises against routine use for diabetic foot ulcers outside clinical trials.

In the United Kingdom, hyperbaric oxygen therapy is recognised for a defined range of clinical indications, primarily where tissue hypoxia, infection, or impaired healing are central to the condition. Internationally, the UHMS and ECHM provide authoritative guidance on accepted indications. In England, NHS commissioning is governed by NHS England's Specialised Commissioning service specification for HBOT, and clinical use is further informed by NICE Guidelines and NICE Interventional Procedures Guidance (IPG).

Routinely NHS-commissioned indications in England (primarily through NHS England Specialised Commissioning) include:

• Decompression sickness — a diving-related emergency caused by nitrogen bubble formation in tissues

• Arterial gas embolism — where gas bubbles obstruct blood flow, often following diving accidents or certain medical procedures

These emergency indications are the primary focus of national commissioning. Other indications may be considered but are subject to local policy, individual funding requests (IFRs), or use within clinical trials:

• Carbon monoxide poisoning — HBOT may be considered in selected severe cases to accelerate elimination of carboxyhaemoglobin and reduce neurological sequelae; however, access varies regionally and referral should follow local protocols and NICE Clinical Knowledge Summary (CKS) guidance on carbon monoxide poisoning

• Clostridial myonecrosis (gas gangrene) — as an adjunct to surgery and antibiotics, subject to local commissioning

• Chronic non-healing wounds, including diabetic foot ulcers — NICE Guideline NG19 (Diabetic foot problems: prevention and management) advises that HBOT should not be used routinely for diabetic foot ulcers outside the context of a clinical trial; access via the NHS therefore typically requires an IFR or research pathway

• Osteoradionecrosis and late radiation tissue injury — NICE Interventional Procedures Guidance has reviewed HBOT for these indications and acknowledges potential benefit in selected patients, whilst noting the need for further high-quality evidence; NHS access is usually via IFR or specialist referral to a regional hyperbaric centre

Patients and clinicians should consult the most current NHS England service specification, NICE NG19, relevant NICE IPGs, and local ICB commissioning policies, as these are subject to periodic review. The BHA can also provide guidance on recognised indications and referral pathways.

What to Expect During a Hyperbaric Oxygen Session

Sessions last 60–120 minutes in a monoplace or multiplace chamber, with gradual pressurisation; patients may experience ear discomfort and should wear 100% cotton clothing, with full treatment courses ranging from 5 to 40 sessions.

For patients referred for hyperbaric oxygen therapy, understanding what the treatment involves can help reduce anxiety and support informed consent. Sessions typically take place in a dedicated hyperbaric unit, either within an NHS hospital or at a licensed private facility. Before commencing a course of treatment, patients undergo a thorough medical assessment to confirm suitability and identify any contraindications.

During a session, the patient enters either a monoplace chamber (designed for one person, filled entirely with oxygen) or a multiplace chamber (accommodating several patients simultaneously, pressurised with air whilst oxygen is delivered via a mask or hood). A typical session lasts between 60 and 120 minutes, during which the chamber is gradually pressurised to the prescribed level. Patients may experience a sensation of fullness or mild discomfort in the ears during pressurisation — similar to descending in an aircraft — which can usually be relieved by swallowing, yawning, or performing a Valsalva manoeuvre. Where clinically appropriate, the treating team may advise the use of a nasal decongestant before a session to reduce the risk of barotrauma; patients should not take any medication for this purpose without first discussing it with clinical staff.

Key practical points for patients include:

• Clothing: Patients are usually asked to wear 100% cotton garments to reduce fire risk; specific clothing and prohibited-item policies follow local hyperbaric unit protocols

• Prohibited items: No lighters, electronic devices, or petroleum-based products are permitted inside the chamber

• Comfort: Patients can read, rest, or watch television during the session in multiplace facilities

• Treatment courses: Depending on the indication, a full course may involve anywhere from 5 to 40 sessions, often delivered daily on weekdays

• Diabetes management: Patients with diabetes should bring glucose monitoring equipment to each session and discuss insulin dosing and meal timing with the clinical team before starting treatment, as prolonged fasting or altered activity levels may affect glucose control

Most patients tolerate HBOT well. Clinical staff monitor patients throughout each session, and the pressure is reduced gradually at the end to allow safe decompression. Further patient information is available from the British Hyperbaric Association (BHA) and individual NHS hyperbaric unit patient leaflets.

Risks, Contraindications and Safety Considerations

Middle ear barotrauma is the most common complication; untreated pneumothorax is an absolute contraindication, and relative contraindications include severe COPD, uncontrolled epilepsy, and certain chemotherapy agents.

Whilst hyperbaric oxygen therapy is generally considered safe when administered in an accredited clinical setting, it is not without risks. Understanding these is essential for both patients and referring clinicians to ensure appropriate patient selection and informed consent.

Common side effects include:

• Middle ear barotrauma — the most frequent complication, caused by difficulty equalising pressure; in rare cases, tympanic membrane rupture may occur

• Sinus barotrauma — pressure-related discomfort in the sinuses

• Temporary visual changes — some patients develop mild myopia after prolonged courses, which typically resolves within weeks of completing treatment

• Oxygen toxicity — at high pressures or with prolonged exposure, excess oxygen can cause pulmonary irritation or, rarely, central nervous system toxicity presenting as seizures; this is carefully managed through established treatment protocols

Absolute contraindications include:

• Untreated pneumothorax — pressurisation can cause life-threatening tension pneumothorax

Relative contraindications requiring careful clinical assessment and specialist risk–benefit evaluation include:

• Concurrent or recent use of certain chemotherapy agents (e.g., doxorubicin, bleomycin) — these interactions are timing-dependent and require specialist consultation and adherence to local protocols before HBOT is considered; they are not an absolute bar in all circumstances

• Severe chronic obstructive pulmonary disease (COPD)

• Uncontrolled epilepsy

• Claustrophobia

• Pregnancy (in non-emergency situations)

• Recent ear or thoracic surgery

• Upper respiratory tract infection or fever (which may impair pressure equalisation)

• Uncontrolled heart failure

• Poorly controlled diabetes

Patients should inform their clinical team of all current medications, as some drugs interact adversely with high-pressure oxygen environments. The Medicines and Healthcare products Regulatory Agency (MHRA) regulates hyperbaric chambers as medical devices in the UK. In England, providers of HBOT as a regulated activity must also be registered with the Care Quality Commission (CQC). Patients are advised to verify that any facility — NHS or private — holds appropriate CQC registration and is recognised by the BHA.

Patients and clinicians should report any suspected side effects or medical device-related incidents to the MHRA Yellow Card scheme (available at yellowcard.mhra.gov.uk), which covers both medicines and medical devices. Patients experiencing chest pain, difficulty breathing, visual disturbance, or seizure-like symptoms during or after a session should seek immediate medical attention.

Accessing Hyperbaric Oxygen Therapy on the NHS or Privately

Emergency indications are nationally commissioned by NHS England; non-emergency access typically requires an IFR, and private session costs range from approximately £150–£300, with patients advised to verify CQC registration before attending any facility.

Access to hyperbaric oxygen therapy in the UK depends largely on the clinical indication and the commissioning arrangements in place within a patient's local NHS Integrated Care Board (ICB) or, for specialised services, NHS England.

For emergency indications — specifically decompression sickness and arterial gas embolism — HBOT is nationally commissioned by NHS England and is available through NHS hospitals with dedicated hyperbaric units; treatment is initiated urgently without prior authorisation. These are the primary indications for which routine NHS commissioning exists in England.

For carbon monoxide poisoning, referral to HBOT may be considered in selected severe cases in line with local protocols and NICE CKS guidance; however, this is not uniformly commissioned nationally and access varies by region and clinical severity.

For non-emergency indications such as diabetic foot ulcers, osteoradionecrosis, or late radiation tissue injury, NHS access is more restricted. As noted above, NICE NG19 advises against routine use of HBOT for diabetic foot ulcers outside clinical trials. For other non-emergency indications, patients may be referred by their consultant to a regional hyperbaric centre subject to individual funding request (IFR) approval, where the treatment is not routinely commissioned. Patients should discuss eligibility with their specialist, who can initiate the appropriate referral pathway.

NHS hyperbaric units are located at a number of hospitals across the UK, including facilities in London, Aberdeen, Plymouth, and Newcastle, among others. The British Hyperbaric Association (BHA) maintains a directory of accredited centres and can provide guidance on both NHS and private provision, as well as emergency referral pathways.

For those considering private treatment, costs can vary considerably — session fees are typically in the range of £150–£300, with full treatment courses potentially costing several thousand pounds. These figures are indicative; patients should request a full written cost breakdown from the provider. Patients are strongly advised to:

• Verify that the facility holds CQC registration (in England) and is staffed by trained hyperbaric physicians

• Obtain a formal medical assessment before commencing treatment

• Be cautious of unsubstantiated wellness claims associated with non-medical or 'mild hyperbaric' HBOT use, which falls outside current evidence-based guidance and recognised clinical standards

If you are unsure whether HBOT is appropriate for your condition, speak to your GP or specialist in the first instance. They can advise on evidence-based options and facilitate referral through the correct clinical pathway.

Frequently Asked Questions