What is hyperbaric oxygen (HBO) treatment?

Hyperbaric oxygen treatment (HBO) involves giving the body extra oxygen. 'Hyper' means increased and 'baric' relates to pressure. Oxygen is one of the gases in the air, and it is essential for life. Normally, oxygen makes up just over one fifth (21%) of air.

In HBO treatment, people breathe in pure (100%) oxygen. This is done by sitting in a chamber known as a hyperbaric oxygen chamber and using a mask or hood.

How does HBO treatment work?

Oxygen is carried around the body by the blood. Breathing in pure (100%) oxygen under increased pressure, called HBO, allows extra oxygen to be taken up by the bloodstream and dissolved more quickly. This extra oxygen can help where healing is slowed down by infection or where blood supply is limited by damage to the tissues.

HBO treatment:

  • increases oxygen levels to normal in areas where they are reduced by illness or injury
  • encourages new blood vessels to grow and carry extra blood and nutrients to the tissues
  • increases the ability of white blood cells to kill bacteria and prevent infection
  • reduces any swelling, pressure and pain that may occur around the area.

Why might I have HBO treatment?

The most common use of HBO is for treating the side effects of radiotherapy. Other uses are being investigated.

HBO treatment for radiotherapy side effects

Radiotherapy can cause changes in the oxygen supply to tissues in the treated area. This is because radiotherapy affects normal cells and blood vessels as well as cancer cells.

The small blood vessels in the treated area can be damaged by radiotherapy. This means that less blood is supplied to that area. When this happens, it becomes more difficult for the oxygen and nutrients we need to reach the tissues.

Over time, the affected tissues may become weaker and start to break down. They may form areas of open sores (ulceration) and rarely, some tissues may eventually die completely (radiation necrosis). These radiation injuries can occur very slowly over months or years.

HBO treatment for radiation injuries works by increasing the oxygen supply to damaged tissue. This encourages new blood vessels to grow and the tissues to heal.

Research has shown that HBO treatment may help treat the following:

Chronic radiation cystitis

Radiotherapy is used to treat some types of pelvic cancer. Sometimes, treatment can lead to inflammation of the bladder (chronic cystitis). Symptoms include:

  • needing to pass urine frequently
  • pain when passing urine
  • blood in the urine (haematuria).

These problems can occur months or years after treatment. Symptoms can be persistent and could be moderate or severe.

HBO treatment may help to improve these symptoms when other treatments have not worked.


Radiotherapy is often used for cancers in the head and neck.

The tissues around this area are easily damaged and may break down after radiotherapy, particularly if you have previously had surgery. Rarely, the bone itself can be affected by radiotherapy and start to break down and die. This is known as osteoradionecrosis. It can also happen when radiotherapy is given to other areas of the body, such as the chest or pelvis.

A research study called HOPON (hyperbaric oxygen therapy to prevent osteoradionecrosis) is trying to find out if giving HBO after radiotherapy to people with head and neck cancer helps to prevent damage to the jaw bone.

When the damage has occurred, treatment for osteoradionecrosis includes:

  • antibiotics
  • washing out the area with salt water (saline irrigation).

Sometimes surgery will be done to remove some, or all, of the affected bone.

HBO treatment may help the tissues around the area of osteoradionecrosis to heal by encouraging blood vessels to grow. However, HBO cannot restore the dead bone.

HBO treatment can also be given before reconstructive surgery to help healing, prevent infection and encourage blood vessels to grow and form new bone.

If wounds or tissue are infected, treatment is usually medicines or surgery as well as HBO treatment.

Tooth removal

Having a tooth removed shortly before, during or after radiotherapy to the mouth and jaw area may increase the risk of osteoradionecrosis. This is because of the reduced oxygen supply to the healing area.

HBO treatment can be given to help prevent osteoradionecrosis. It should be given before and after the tooth is taken out, and to help the healing process.

Chronic radiation effects on the bowel

Radiotherapy can be given for bowel cancer. The bowel is very sensitive and rarely, radiation damage can cause long-term symptoms. These include:

  • pain
  • bleeding
  • irregular bowel habits.

HBO treatment may help improve these symptoms when other treatments, such as anti-inflammatory medicines, have not worked.

How is HBO treatment given?

Your hospital specialist can advise you on whether HBO treatment is appropriate in your situation. They may refer you for HBO treatment if you have long-term side effects from radiotherapy treatment that have not responded to standard treatments.

There are a number of places where HBO treatment is given. Your doctor will be able to tell you where your nearest centre for treatment is. Some people may have to travel a long way.

Before having HBO treatment you will be examined by a doctor to make sure that you are fit enough to have it. HBO treatment is suitable for most people. It is given inside a chamber, so if you have a fear of enclosed spaces (claustrophobia), you may need medicines to help calm you.

Treatment sessions are likely to be delayed if you:

  • have a severe cold or flu
  • have a runny nose
  • have sickness (nausea)
  • are generally feeling unwell.

You should let your nurse or doctor know if you have any of these symptoms before starting a treatment session. You may want to phone the HBO treatment unit to discuss this before travelling.

If you smoke, you will be asked to stop smoking before and during treatment. This is because smoking is likely to affect the level of oxygen in your body. No smoking materials, such as matches or lighters, are allowed in the chamber.

Before treatment you will be given some cotton clothes to wear. You are not allowed to take certain items into the chamber, including:

  • mobile phones
  • watches
  • pens.

The staff at the unit will give you more information.

You will be advised to go to the toilet before your treatment, although some chambers have toilets. Talk to the nurse if you are worried about needing the toilet during your treatment.

Treatment is usually painless and is carried out in simple chambers. There are two types of chamber:

  • Monoplace chambers

    These are designed to treat one person at a time. Treatment involves lying on a 2.1m (7ft) padded stretcher that slides into a clear plastic tube (chamber) that is about 60cm (2ft) wide.

  • Multiplace chambers

    These are designed to treat up to 12 people at a time, and are more commonly used than monoplace chambers. These chambers are quite large and you will be able to walk about inside.

Compression phase

Once you are sitting or lying inside the chamber, the doors will be closed and air is blown into the chamber to increase the pressure. As the air begins to circulate, you will hear a hissing sound, similar to that in an aircraft. The chamber will feel warmer.

In both monoplace and multiplace chambers it is necessary to clear your ears as soon as the pressure begins to increase. You will be shown how to do this. Clearing your ears helps to balance the pressure in them and prevent any pain in your eardrum.

Treatment phase

When the pressure reaches the correct level, you will usually be asked to put on either a mask or a clear hood to get pure (100%) oxygen. Monoplace chambers are pressurised using 100% oxygen, so you might not need to wear a mask or hood.

During treatment you will be able to relax, read, listen to music or watch TV, if the chamber has one. You will be able to see and talk to a member of staff at all times during the treatment.

The length of each treatment depends on what you are being treated for. It can last from 60 to 90 minutes at a time.

Decompression phase

Near the end of the treatment, the pressure in the chamber is slowly lowered. You may feel popping in your ears during this time. As the chamber decompresses it will begin to feel cooler. After the decompression phase you can leave the chamber.

Treatments are usually repeated over a number of days or weeks. You should complete the whole course for the most benefit.

Possible side effects of HBO treatment

HBO treatment is very safe and does not cause many side effects. They are usually minor and do not last long. If you notice any other problems that you think may be caused by the treatment, speak to your nurse or doctor.

  • Blurred vision

    This can occur after having several treatments. It is caused by the development of short sightedness (myopia). It usually comes on gradually and then gets better slowly when treatment ends. Using glasses or changing your prescription for a short time may help, but the blurred vision only lasts a few weeks at most.

  • Light-headedness

    Some people feel light-headed after treatment. This only lasts for a few minutes.

  • Fatigue

    Tiredness is a side effect that can be more of a problem if you have treatment more than once a day. The effect usually wears off after a few days once the treatment sessions are finished.

  • Ear problems

    Although uncommon, damage to the eardrum can occur due to the change in pressure. Before treatment you will be shown how to equalise the pressure in your ears, which can help to prevent any ear problems.

Less common side effects of HBO treatment

  • Painful sinuses

    The change in pressure may cause discomfort if you have congested sinuses, leading to headaches or facial pain. Usually this can be controlled with decongestant medicine, but sometimes HBO therapy needs to be stopped.

  • Effects on the lungs

    Very rarely HBO treatment can damage the lungs. This usually only happens if HBO is given over a long period of time.

Clinical trials for HBO treatment

As well as helping to improve some of the side effects of treatment, hyperbaric oxygen treatment may also be helpful when used alongside some cancer treatments. Research is trying to find out if HBO can:

  • help reduce the growth of some types of cancer when used in combination with radiotherapy
  • improve the effects of chemotherapy.

Cancer specialists use clinical trials to assess new treatments. Before any trial is allowed to take place, an ethics committee must approve it and agree that the trial is in the interest of the patients.

You may be asked to take part in a clinical trial. Your doctor will discuss the treatment with you so that you have a full understanding of the trial and what it involves. You may decide not to take part, or to withdraw from a trial at any stage. You will still get the best standard treatment available.