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Hyperbaric Facility Saving Lives Under Pressure

Dr Mark Glover, Director of the Qinetic Hyperbaric Medicine Unit in Gosport, stands inside the decompression chamber [Picture: Defence Codex]
Navy diver and support team
Dr Mark Glover inside the decompression chamber [Picture: Defence Codex]

Last year's Maritime Strategic Capability Agreement (MSCA) between MOD and QinetiQ secured access to a range of maritime engineering and scientific expertise and facilities, including the Hyperbaric Medicine Unit in Gosport.

It would be easy to be overawed at first sight of the decompression chamber at the Hyperbaric Medicine Unit but its Director, Dr Mark Glover, is reassuring:

"The chamber at Haslar and its satellite facility at Queen Alexandra Hospital Cosham together form a Category 1 Unit which can receive patients ranging from the critically ill to the ambulant. It is used in recompression therapy for divers and for other medical conditions such as carbon monoxide poisoning and radiation tissue injury."

The size, weight and design of the chamber are impressive. The large steel cylinder has an external diameter of 2,438mm and a hull thickness of 13mm.

The addition of an arched doorway into the main chamber makes it feel less claustrophobic. A manlock at the opposite end allows large equipment to be passed through and staff or patients withdrawn without disturbing treatment.

Patients are kept comfortable and at ease in the environmentally-controlled Unit which has a speak-to-speak circuit keeping them in contact with Glover and his team. There is also a medicine airlock which allows patients who require drugs to get these quickly and easily, although Glover admits this is more usually caffeine and pizza!

Glover explains that the oxygen needed for treatments is delivered through hoods which are gas tight but comfortable to wear. Oxygen runs through these at 35 litres per minute, giving each patient their own 'oxygen atmosphere'. The main compartment has accommodation for five seated patients (or fewer in a combination of seated and lying).

The bends, or more correctly decompression illness, is often caused by divers returning to the surface too quickly. On descent, flexible air spaces within the body such as the lungs provide no support or resistance against greater outside pressure and can contract.

A diver usually breathes from a compressed gas supply which allows the lungs to resist the external compression and to remain at normal volumes. Some of the pressurised gas gradually dissolves in the tissues of the body during the dive. On the returning ascent the gas in the lungs expands when the outside pressure decreases and this expansion, if too rapid, can lead to lung rupture and escape of bubbles into the bloodstream.

Also, the excess dissolved gas is released from the tissues as pressure falls and this often results in formation of bubbles, especially in the blood. Wherever they originate, it is these bubbles that cause decompression illness if they are in sufficient numbers. This can happen from holding the breath or ascending too quickly.

When large bubbles of gas interfere with the flow of oxygen-rich blood to the central nervous system, lungs or heart, they can rapidly result in death or severe disability. More often the bubbles cause mechanical damage to the lining of blood vessels resulting in symptoms which are usually less serious but sometimes quite distressing. The bubbles can also cause permanent damage to the bones which has no immediate symptoms and reveals itself some time after the causal decompression incident.

To treat the bends, Hyperbaric Oxygen Therapy (HBOT) delivers oxygen to the patient at greater than atmospheric pressure. The patient receives up to 14 times the normal amount in a pressurised chamber and the combination of increased oxygen and pressure allows the blood to carry greater amounts of oxygen to the area of the body that needs healing.

"In the majority of diving cases 100 per cent oxygen is delivered at a pressure of 2.8 bar," says Dr Glover. "Deeper dives and more serious cases might need other gases to be added to make a therapeutic mixture which provides more pressure while avoiding oxygen poisoning."

Last year they treated 18 divers but their workload can vary from 10 in one year to over 50 in another. The number of treatments per patient also varies with most people requiring one or two visits to the chamber, although other facilities have recorded instances where many more visits were required. Treatments at Gosport are recorded on digital TV and video which means the Unit can audit themselves following an adverse event.

Another part of their role is to train Royal Navy Service Medical Officers. This adds to the officer's theoretical training, equipping them to deal, on-scene or remotely, with diving emergencies which may happen on an overseas deployment or on the back of a mine hunter:

"Divers often act as the hands and eyes of the doctor and will pass information to the medical officer," says Dr Glover. "Sometimes there will be a doctor or other medical branch serviceman who can assess the condition at the incident but they will still need to be talked through the treatment.

The combination of increased oxygen and pressure allows the blood to carry greater amounts of oxygen to the area of the body that needs healing.

"In both cases the Diving Medical Officer must have a thorough understanding and experience of the practical aspects of hyperbaric treatments."

The Unit's main purpose is to mitigate the effects following military diving incidents or accidents in the Portsmouth area where most diving and submarine training takes place.

The RN Diving and Hyperbaric Medicine Division (which is responsible for medical aspects of diving across the services) are also based in Gosport and use the Unit for training.

As military accidents are infrequent, the opportunity for RN diving specialists to treat civilian casualties and patients with less urgent conditions is a valuable training resource. Glover believes that this is an important part of their role:

"They are able to work on people who are not urgently unwell and it allows them to familiarise themselves with the equipment and how to look after people in the chamber," he says.

RN Diving and Hyperbaric Medicine Division

The Royal Navy is the lead Service for all military diving. The main aim of the Diving and Hyperbaric Medicine Division is to improve the operational capability of RN diving by promoting health and safety and maximising their effectiveness. It acts as the final authority in the assessment of medical fitness for all types of Service diving and on the development of safe diving policy for the Military Diving Safety Management System.

The Division provides on-site consultant support to manage casualties and Medical Officers and also provides on-site support to high risk activities such as diving trials and submarine escape and rescue exercises.

For other military diving incidents elsewhere in the world, the Division operates a round-the-clock Diving Incident Telephone Advice Line.

QinetiQ own and run the Hyperbaric Medicine Unit and provide a Medical Director, technical staff, a state-registered paramedic and three hyperbaric nurses. The Institute of Naval Medicine provides the medical officers with hyperbaric expertise. The host hospital trust (Portsmouth Hospitals NHS Trust) provides support services including the Intensive Care Unit (ICU) and other medical specialities required to look after the patients during and between treatments.

This article first featured in the Spring 2009 issue of Defence Codex - The Journal for Defence Engineering and Science.