Decompression, recompression… Making sense of hyperbaric chambers.

Decompression, recompression… Making sense of hyperbaric chambers.

We have all heard the words ‘In the unlikely event of an accident’ during a dive briefing and seldom even give it a second thought. An unplanned trip to a recompression chamber is not always something we consider when planning a dive holiday filled with sun, fun and lots of diving. We have found some information on hyperbaric chambers, how they work and what to expect if the unlikely was to happen.

Hyperbaric chambers

A Hyperbaric chamber is a tiny room- capsule if you will- that is large enough to hold two or more people at a time depending on the facility. The chamber is sealed while the pressure inside the chamber as well as the oxygen content is slowly increased.

Different ambient pressures can be reached and kept inside the chamber.

While a diver is submerged the higher ambient pressure leads to a higher absorption of nitrogen into the body tissues. Upon surfacing the pressure around a diver’s body decreases drastically leading to the evacuation of the absorbed nitrogen. While other factors could put divers at higher risk of getting Decompression Illness, it usually happens when a diver either stays too deep for too long (absorbing larger amounts of nitrogen), or ascends too quickly (resulting in an accelerated release of nitrogen). When nitrogen moves out of a diver’s cells too quickly it forms bubbles – leading to the diver experiencing DCI symptoms and needing to go into a hyperbaric chamber.

The chamber simulates a higher ambient pressure, recompressing the nitrogen bubbles. The pressure is then slowly decreased to allow slow degassing of the nitrogen from the diver’s tissues.

At the same time the partial pressure of oxygen in the body tissues increases. This is called hyperbaric oxygen therapy – where a higher blood oxygen content leads to increased healing of body cells. Basically the body heals itself more efficiently when exposed to higher concentrations of oxygen.

Decompression chambers vs Recompression chambers

Hyperbaric chambers can be categorised in to two types in relation to scuba divers: Decompression chambers and Recompression chambers.

Recompression chambers are used to treat DCI in scuba divers. They can also be used to prevent DCI in certain cases.

Decompression chambers are used for surface-supplied divers. Surface-supplied divers are usually commercial divers who spend long amounts of time under water. The chamber allows the divers to decompress out of the water instead of making their decompression stops while submerged. Decompression chambers can either be in the water or, more commonly, on land.

So, where is the closest chamber to this island?

Ask this to the dive centre staff at your dive destination and it might not be uncommon to hear that the closest hyperbaric chamber is at least a couple of hours’ flight away. It is important to make sure that you know where the closest hyperbaric chamber is to your dive location, approximately how long it would take to get there and whether there is ample emergency oxygen for the trip.

Speaking to the dive centre about their emergency plans will not only prepare you in the unfortunate event of a dive emergency but will also give you some insight about the safety procedures that the dive centre has in place.

I have to go to a chamber – what can I expect?

Amir Hadanny from The Sagol Center for Hyperbaric Medicine and Research [P1] and colleagues found that between 76 and 78% of patients who were treated for DCI in a hyperbaric chamber recovered fully. Late recompression (48 hours or longer after the accident occurred) showed to be nearly as effective as immediate treatment especially if the treatment is based on the U.S. Navy Table 6. However, timely treatment of DCI is vital to decrease the size of the nitrogen bubbles and avoid any additional injury.

Treatment takes at least a few hours. If the U.S. Navy Table 6 model is used, patients will be compressed to the depth of 18m while breathing oxygen, then slowly decompressed to 9m and eventually reach surface pressure. This procedure usually takes around 4hours and 45 minutes.

Treatment might span over a number of days with the longest on the first day and getting shorter each day after that. Treatment will continue until the patient reaches a ‘treatment plateau’ and show no symptoms between treatments.

Once treatment is completed the medical professional will advise the diver on when s/he can dive again. Medical clearance should be given before a diver returns to the water.

The importance of dive insurance

The cost of hyperbaric treatment including hospital bills, doctors’ fees and transportation to the facility (often with a helicopter) could easily reach tens of thousands of dollars. Having a good dive insurance like DAN is vital. Dive insurance companies offer a variety of plans ranging from cover for a few days to yearly and even lifetime cover. It is definitely worth investing in comprehensive dive emergency cover for your next dive trip.

According to DAN[P2] , the injuries sustained by the accumulation of a number of small bubbles could cause as much damage as a car accident. If you suspect that you have DCI, do not delay treatment. Start breathing 100% oxygen and contact your medical professional or dive insurance company to assist a speedy transfer to the nearest Hyperbaric Chamber. Cutting your holiday short is a small price to pay for another day of diving.

*A version of this article first appeared at

Juanita Pienaar

Juanita Pienaar is a citizen of the world, recently settled back down in her home country, South Africa, after spending time traveling and living in Asia and Africa. She has a passionate love affair with the ocean and loves to share that passion by teaching scuba diving. She is a yoga teacher and fully believe in finding the balance in life. She has recently discovered the joy and freedom of wearing yoga pants ‘out-and-about’. Juanita loses herself in the written and spoken word.

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