Dear Alban:
Here are some quick answers to your questions. Sorry to be so brief at this time.
Could O2 delay the symptoms of DCS?
Most definitely oxygen could not only delay the appearance of DCS. If it were delayed long enough, all nitrogen would diffuse away and DCS would not appear.
Could a diver suffering from DCS have his judgment impaired?
It the diver had neurologic decompression sickness (in the brain, not the spinal cord), it is definitely possible to have cognition (= judgment) problems.
Is it true the diver is at the greatest risk in the 60 minutes after surfacing ?
Most problems associated with decompression sickness will appear within sixty minutes.
Is it true a diver suffering DCS may not feel pain ?
If it is joint-pain DCS, the diver will feel it. If it is neurological DCS, there is generally not any pain associated with it (although there might be numbness or itching). This form manifests itself in difficulties in moving arms and legs, balance, speech, and facial muscles.
If a diver waits until pain, might irreversible damage have occurred ?
If it is pain-only DCS, there is not any irreversible damage. Unfortunately, there might be nerve injury in addition to the joint pain. In this case, there could be "neurologic residuals."
Will O2 alone prevent DCS in all but mild cases ?
No, oxygen is not an all-purpose cure. The balance between nitrogen moving to the capillaries and moving towards to bubbles is what initially causes the DCS process. Naturally, the greater the dose of nitrogen, the larger will be the bubbles. Oxygen changes the equation by allowing no nitrogen at all to back flow into the tissue from the arterial system.
Dr Deco :doctor: