This is an alternative Protocol by Dr Carl Edmonds of the Australian Navy School of Underwater Medicine for treatment of DCS in water at a shallower depth, as suggested by John Lippmann.
In-water Oxygen Treatment Procedures Oxygen should be supplied at maximum depth of 9 msw (30 fsw), from a surface supply system. The ascent is commenced after 30 minutes in mild cases, or 60 minutes in severe cases, if significant improvement has occurred. These times may be extended for another 30 minutes, if there has been no improvement.
The ascent is at the rate of 12 minutes per metre (4 minutes/foot). A diver attendant should always be present, and the ascent controlled by the surface tenders. The duration of the tables range from 2 hours 36 minutes or 3 hours 6 minutes depending on the treatment options used.
After surfacing the patient should be given periods of oxygen breathing, interspersed with air breathing, usually on a one hour on, one hour off, basis, with respiratory volume measurements and chest X-ray examination if possible. The treatment can be repeated twice daily, if needed.
The equipment required for this treatment is similar to that used in a surface supplied oxygen decompression system with some important differences. In the case of an in-water treatment, a G size cylinder (220 cubic feet or 7000 litres) of medical oxygen is probably adequate though specific requirements can easily be calculated. This is usually available form local gas supply companies or hospitals, although in some cases industrial oxygen has been used.
For a diver at rest, breathing this volume of oxygen at a depth varying between 9 meters (30 feet) and the surface is usually insufficient to produce either neurological (CNS) or respiratory oxygen.
Note that all equipment used with pure oxygen must be rated for oxygen service. Also, whenever oxygen is given, the cylinder should be turned on slowly and the flow commenced, before it is given to patients or divers. A 2-stage regulator, set at 550 kPa (80 psi) is fitted with a safety valve, and connects with 12 metres (40 feet) of supply hose. This allows for 9 metres depth, 2 metres from the surface of the water to the cylinder, and 1 metre around the diver. A non-return valve is attached between the supply line and the full face mask.
The full face mask is critical as it enables the system to be used with a semiconscious or unwell patient. It reduces the risk of aspiration of sea water, allows the patient to speak to his attendants, and also permits vomiting to occur without obstructing the respiratory gas supply. The supply line is marked in distances of 1 metre from the surface to the diver, and is tucked under the weight belt, between the diver’s legs, or is attached to a harness. The diver must be weighted to prevent drifting upwards in an arc by the current.
In-water air treatment of DCS is not to be undertaken lightly, however, in the absence of a recompression chamber or other options, it may be the only treatment available to prevent death or severe disability.
Dr.Carl Edmonds is a founding member of the South Pacific Underwater Medicine Society (SPUMS).