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Slark Hyperbaric Unit | Waitematā | Te Whatu Ora

Public Service, Respiratory, Dermatology, Emergency, Occupational Medicine


Hyperbaric Oxygen Therapy (HBOT)

Hyperbaric oxygen therapy has proven to be of value in the treatment of various conditions from decompression illness and carbon monoxide exposure to the treatment of chronic non-healing wounds and radiation damage.

Hyperbaric oxygen therapy is the administration of 100% oxygen at pressures greater than normal atmospheric (sea level) pressure. However, to be effective, the pressure must be greater than 2 atmospheres.
You will be treated at the appropriate pressure that has proven to be the most effective in the treatment of your condition.

Oxygen Administration

Hyperbaric oxygen therapy is provided by first pressurising the recompression chamber with air. You then breathe oxygen through a snugly fitting mask or an oxygen hood. This is the “treatment”.

During this treatment period you may sit in a chair or lie on a bunk and read a magazine or just listen to the radio. The length of each treatment will vary depending on the dose of oxygen prescribed but the treatment period is punctuated with regular 5-minute breaks from the oxygen mask or hood. The timing of these breaks is quite crucial and you will be advised when you may take a break.


There will always be an attendant in the recompression chamber with you, who has been trained to monitor your progress and well-being. The chamber attendant will also carry out the occasional minor technical task to ensure your safety and comfort. The chamber can accommodate 5 patients so there will usually be others for company.

Chamber Operation

The diving supervisor, who is always available outside the chamber, is responsible for maintaining your safety and comfort and for keeping an accurate record of pressure and timing for the treatment. Pressurisation of the chamber is a noisy process. Ear defenders can be worn during pressurisation and during any periods of ‘flushing’ the chamber atmosphere. The chamber atmosphere is continuously monitored at the control panel and the attendant regularly gives ‘weather’ reports.


You will be asked to remove your outdoor clothing, put on one of the “scrub” tops and bottoms which are made from cotton fabric. Please chat to staff if you think this will be a problem.  Occupants entering the chamber remove their shoes and ensure they are not carrying any “prohibited” goods such as oil or grease that may be on shoe soles. The door is shut and everyone may don ear defenders if required. Pressurisation begins and you start to “equalise your ears”. Once the required pressure is reached assistance is given to put on your oxygen mask or hood. Then you breathe normally. The attendant will instruct you what to do and when.

Possible Complications

Because the chamber is a relatively confined space in which oxygen is being administered, all possible measures are taken to minimise the risk of fire. All flammable materials are “prohibited” from the chamber and reading material is limited to one book each.

Clothing is restricted to the issued scrubs, t shirts and tops or sweatshirts worn over your own underwear. No cigarettes, matches, lighters, electronic gadgets including cellular phones, alcohol or oil based fluids are permitted. Pens are also restricted from entry into the chamber but pencils are fine. Most normal wristwatches are not made to withstand changes in pressure so unless yours is a diving watch you are advised not to wear it during a treatment.

If you have questions about any item please do not hesitate to ask the attendant or the diving supervisor.

The effect of pressure changes on your middle ears requires you to actively “clear your ears”. You will be coached to do this and you should begin “clearing your ears” from the very start of pressurisation. If at any time you feel the slightest discomfort in your ears, please inform the attendant immediately and help will be given.

Some techniques to clear your ears include swallowing, yawning, clicking your jaw, turning your head, holding your nose and breathing out against a closed throat (valsalva), chewing gum or drinking water.

Breathing oxygen at high pressures may also cause a reaction similar to an epileptic fit in some susceptible people. This is a relatively rare occurrence. If you do suffer such a reaction you will suffer no after-effects from it. Prior to this reaction happening the person would feel ‘odd’, perhaps nauseated, may have some changes in vision or hearing or even feel twitches in their lips or face. If you ever feel anything out of the ordinary that concerns you please promptly inform the attendant.

Following Treatment

If you are being treated for decompression illness you are advised not to dive, fly or ascend to an altitude of 300 metres or more above sea level for one month following your initial injury. If you are being treated for any other medical condition these restrictions do not apply to you, although you should discuss any plans to fly on the same day as treatment with one of the medical staff.

Your Health

If you have a cold you may not be fit to 'dive' because you may not be able to clear your ears or your sinuses may not be able to “equalise” themselves. Please inform the staff at any time if you feel unwell. If you are to have a prolonged course of treatment and you wear glasses for reading you may find that your vision has improved. This is a temporary change and you are recommended not to change your glasses over the course of the treatment or for a short period afterwards.

If you have cataracts you are advised to have an ophthalmologist examine your eyes prior to diving as cataract progression may be affected by hyperbaric oxygen. From time to time, staff may repeat lung function or eye tests, which you may have had prior to commencing treatment, this is routine.

Please do not hesitate to ask the staff about any aspect of your treatment and progress.

This page was last updated at 2:14PM on March 6, 2024.