The correct first aid for the DCS is :
Every time we suspect the DCS it is important to start a 100% oxygen inhalation as soon as possible despite seemingly light symptoms.
Even though this procedure used to be recommended as a gas embolism prevention, it is now considered obsolete. The method increases the intracranial pressure and therefore worsens the haematoencephalic barrier damage.
Correct! When suspecting a DCS it is very important to immediately start a 100% oxygen inhalation (a 100% oxygen cylinder is a mandatory equipment of all diving centers). Early oxygenotherapy highly increases the efficiency of the following therapy, less severe symptoms of DCS can even be completely cured by it. As scuba diving causes dehydration and dehydration worsens the progression of DCS, fluid substitution is always a part of the first aid. When suspecting a DCS we always
contact the EMS.
In general, underwater recompression is not considered a safe treatment option. Trouble with the air flow, hypothermia, possible oxygen toxicity, dehydration and uncontrolled environment are less than ideal and bare the risk of drowning. Under specific conditions this method can be used for example by the Navy SEALs forces - which we are definitely not.