<unk>  (IWR) or underwater oxygen treatment is the emergency treatment of<unk>  sickness (DCS) by returning the diver underwater to help the gas bubbles in the tissues, which are causing the symptoms, to resolve. It is a procedure that exposes the diver to significant risk which should be compared with the risk associated with the available options. Some authorities recommend that it is only to be used when the time to travel to the nearest<unk>  chamber is too long to save the victim's life, others take a more pragmatic approach, and accept that in some circumstances IWR is the best available option. The risks may not be justified for case of mild symptoms likely to resolve spontaneously, or for cases where the diver is likely to be unsafe in the<unk> , but<unk>  may be justified in cases where severe outcomes are likely, if conducted by a competent and suitably equipped team. Carrying out<unk>  when there is a nearby<unk>  chamber or without suitable equipment and training is never a desirable option. The risk of the procedure is due to the diver suffering from DCS being seriously ill and may become paralysed, unconscious or stop breathing while under<unk> . Any one of these events is likely to result in the diver drowning or asphyxiating or suffering further injury during a subsequent rescue to the surface. This risk can be reduced by improving airway security by using surface supplied gas and a helmet or full-face mask. Several schedules have been published for<unk>  treatment, but little data on their efficacy is available.
In-water recompression
Aeromedical evacuation
Reperfusion therapy
Hemoperfusion
Extracorporeal shockwave therapy
Mouth-to-mouth resuscitation
Extracorporeal cardiopulmonary resuscitation
Perfusion