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About the Hyperbaric Medicine Unit

Inside the recompression chamber

Inside the Hyperbaric Medicine Unit's recompression chamber


Hyperbaric oxygen therapy is the delivery of oxygen at greater than atmospheric pressure and has been used for many years to treat decompression illness (the bends); typically suffered in diving accidents.

It is now recognised that it also has potential as a therapy for several additional conditions; particularly when used in conjunction with other medical and surgical interventions.

The Hyperbaric Medicine Unit (HMU) is registered with the Care Quality Commission. It can treat emergency and non-emergency patients for the NHS; and patients referred under other arrangements.

It is a Category 1 facility and can take patients who need intensive care during the treatment.

Recompression chamber facts and figures



  • We have a Royal Navy Type A recompression chamber modified with an arched doorway into the main chamber to make access easier for patients
  • There are two compartments – a 7m³ 'man lock' and 19m³ main chamber
  • The chamber can accommodate five people sitting; two lying down; or three sitting and one lying down
  • Its maximum pressure setting is 8.5 bar – equivalent to a depth of 85 metres at sea
  • The chamber's environmental control system regulates its temperature and humidity and removes carbon dioxide





The chamber is owned and operated by QinetiQ who provide the unit's medical director, technical staff, hyperbaric nurses and attendants, and some of the diving doctors.

The Ministry of Defence funds the provision of the service in support of military diving and doctors from the Institute of Naval Medicine participate in the rota for medical cover.

Western Sussex Hospitals NHS Trust provides support services to the HMU; including the intensive care unit and other medical specialties needed to look after patients between treatments.

History of the HMU

Research into diving and decompression treatments began during the Second World War with the formation of the Royal Navy Physiological Laboratory (RNPL) at Alverstoke; in Gosport.

The naval life support work of the RNPL led to the development of the HMU at Royal Haslar Hospital; in Gosport. The unit moved to St Richard's Hospital; Chichester; in March 2010.