During a dive, Nitrogen is absorbed by the body (Boyle’s Law), and the body tissues become saturated with the gas. When a diver ascends too quickly, the nitrogen gas in the tissues will come out of solution and expand at such a rate that the body is unable to eliminate it efficiently, and the nitrogen will form small bubbles inside the tissues. This is known as decompression illness (DCI), commonly called ‘The Bends’, which can be very painful and lead to tissue death or may even be life-threatening. DCI encompasses decompression sickness (DCS) and arterial gas embolism (AGE). For the second one, small ruptures in the lungs can be caused, leading these tiny bubbles to enter the arterial circulation, travel through the body, and eventually lodge in blood vessels and block blood flow. The risk of permanent physical or neurological deficit could affect the future livelihood of the diver and their quality of life.
What this means for the captain and crew on board, especially when sailing in remote areas, is that time is ticking. The priority remains in keeping the patient stable and hydrated whilst providing O2 until evacuation to the nearest decompression chamber is arranged. However, the question marks are too many – if there is a nearby recompression chamber, if it is working safely and being operated by trained personnel, and if evacuation is possible at a low altitude.
Hyperbaric Oxygen Therapy (HBOT) has a proven track record for treating DCS and AGE, which is provided using a recompression (or hyperbaric) chamber. What a recompression chamber allows us to do, in simple words, is to bring the diver back under pressure and, when at the treatment depth, provide pure oxygen for an extended period by following a treatment table.
Recompression chambers have been part of the Navy – and Research – vessels for decades and are usually large metallic structures stored inside bulky twenty-foot containers. Several larger yachts worldwide incorporate one of these large, fixed metallic chambers on board. However, due to size, space, fixed facility regulations and weight restrictions, this is not usually preferable for most yachts, where space comes at a premium.