What is Hyperbaric Oxygen Therapy (HBOT)?

Hyperbaric oxygen therapy is the administration of oxygen at a higher than normal atmospheric pressure, that is used to treat a limited but diverse range of illnesses. It is the primary treatment for disorders such as decompression illness, arterial gas embolism and carbon-monoxide poisoning.

It is also an effective adjunct in a combined program involving dressing changes, surgery and antibiotics for the enhancement of healing in non-healing 'problem' wounds.

This includes:

  • radiation tissue injury (both soft tissue and bone) ,
  • selected problem wounds including diabetic ulcers,
  • chronic osteomyelitis
  • crush injuries, and
  • Some skin grafts and flaps. 

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How does Hyperbaric Oxygen Therapy work?

Hyperbaric oxygen therapy is the medical use of 100% oxygen at increased pressure. It works in a variety of ways in the body. This increased pressure provides more oxygen to the body than is possible under normal conditions. Most treatments are between two and three atmospheres of pressure, and the pressure change closely approximates scuba diving.

This increase of pressure drives more oxygen into body tissues and wounds that are lacking adequate levels of oxygen (called hypoxia) speeding wound healing and helping the return of normal tissue functions. 

How often are Treatments Given?

The length and frequency of treatments is worked out for each person and the condition. Hyperbaric oxygen may be an important part of total care, including wound care, surgery and medication as indicated.  For most patients, treatments are daily - Monday through Friday - and treatments may last 2 - 2 1/2 hours. Some emergency conditions will require only one or two treatments. In most cases of wound healing support, the effects are gradual, and 20 to 50 treatments may be required.

Who gives me my HBOT Treatments?

Christchurch HMU has doctors who have had specialised hyperbaric medical training. The medical team includes anaesthetists and General Practitioners.

While in the chamber, treatments are managed by either a Registered Nurse or Diving Medical Technician with specialised training in hyperbaric medicine. An attendant is always in the chamber throughout treatment. The treatment is managed outside the chamber by a technician trained in pressure chamber operations. Medical care is rapidly available during treatments.

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What will I feel during the HBOT treatment?

Everyone feels fullness in their ears as their eardrums adjust to the change in the chamber pressure. This is very similar to the feeling experienced when in an airplane or elevator. Instruction will be given on how to 'clear' ears, or equalize the pressure before treatment.  If anyone experiences pain in their ears, the treatment is paused briefly until they are better.

Once the treatment begins air hisses into the chamber and it gets warmer.  This will return to normal once the treatment pressure is reached.

During the treatment patients breathe from a special oxygen circuit through either a close fitting face mask or a clear plastic head-hood.

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The attendant is there to deal with any problems straight away.

What are the risks and benefits of HBOT? 


Depending upon the reason for coming to the Hyperbaric Medicine Unit, treatment can provide one or more of the following benefits:

  • Increased oxygen delivered to injured tissue
  • Greater blood vessel formation
  • Enhanced wound healing
  • Improved infection control
  • Preservation of damaged tissue
  • Elimination of toxic substances
  • Reduced effects for toxic substances
  • Reduction or elimination of tissue obstruction by gas bubbles 


There are risks to HBOT, but most of them can be dramatically reduced with the proper management. The risks can be divided into two types, physical and safety risks.

Physical Risks

    • Ear Discomfort
      The increasing pressure in the hyperbaric chamber can cause ear discomfort and injury to eardrums.  If unable to equalise the pressure by swallowing or yawning, a surgeon can make a small temporary hole in the eardrum, as used in children with 'glue ears'. This is called a myringotomy, and will heal quickly once treatments are finished.  About 15% of patients have some degree of problem with clearing ears, this is usually only minor.
    • Oxygen Toxicity
      Oxygen toxicity can occur, affecting less than 1 person in 3,000-10,000, only once every few years in Christchurch.  Signs of oxygen toxicity are tingling in the fingers, nausea, dry cough, chest pain and convulsions. Recovery is rapid and complete, although alarming when it happens.
    • Visual Changes
      During a long course of HBOT a reduction in visual acuity may be noticed. This is reversible in nearly all patients, returning to pre-treatment levels over several weeks or months. Sometimes this may interfere with such things as reading road signs from a distance, so extra care may need to be taken during the course of treatment.
    • Other Physical risks
      Other uncommon problems caused by the pressure change are pain in the sinuses or in teeth with poor fillings or cavities. On very rare occasions, damage to lungs may cause serious injury or death.

Safety Risks
Fire is a higher risk when the chamber is under pressure because of the increased level of oxygen in the hyperbaric chamber. All patients and staff remove all extra items that might be a hazard.

Items that cannot be taken into the chamber:

  • cigarettes
  • lighters
  • matches
  • excess paper (other than 1 reading item)
  • newspaper
  • jewellery/watches (other than diving watches)
  • metal objects
  • contact lenses
  • hearing aids
  • cell phones or any other battery operated device
  • hand/pocket warmers and heat pads

Patients will be asked to remove anything with oil in it, such as:

  • lipstick
  • hair oil
  • hair spray
  • ointments
  • linaments
  • makeup
  • cologne or perfume

Staff will arrange clothing to wear during the treatment.  An undershirt of 100% cotton may be worn, to reduce the risk of electrostatic sparking.

Clothing not allowed in the chamber includes:

  • wool, silk or synthetic textiles
  • nylons
  • polypropylene 

What else do I need to know? 

  • For nearly all patients, treatment is painless and uneventful but takes up a lot of time and may get rather boring.
  • No smoking 2 hours prior and 2 hours after treatment. Smoking decreases the amount of oxygen that can be transported by the blood. It is very strongly advised that patients do not smoke during the course of treatment as it reduces the likelihood of the HBOT working properly. Advice on smoking cessation is available from the nurses. 
  • People with diabetes on Insulin need to take their insulin and regular diet prior to treatment and, during the treatment, a suitable snack will be provided.
  • Go to the toilet before the start of each treatment.
  • Remove contact lenses and hearing aids before your treatment.
  • Avoid fizzy drinks for 2 hours prior to your treatment.
  • Ring the unit for any cancellations, but treatments should be daily.
  • Get a flu vaccine and avoid people with coughs and colds during treatment.  Getting a cold may make ear clearing difficult for a week or two.
  • Any questions or concerns talk to your hyperbaric doctor or nurse



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Page last reviewed: 13 September 2013