In my HEMS days (many moons ago) I had one of these calls.
A diver with the bends, ground ambulance called us because of the long road transit time.
I flew the guy at 200 ft AGL (clear of built up areas etc, flat open country, cavok and twin engine) to the nearest decompression unit which was just over half an hour away.
Later a discussion ensued with my CP about the chosen flight altitude. But due to lack of proper reference we agreed to disagree.
I had chosen my altitude based on my limited knowledge about decompression, with information from the doctor on board. I kept the flight as safe as possible for all, both airborne and on the ground, and as short as possible.
Unfortunately the diver did not make a complete recovery. Perhaps it would have been better in hindsight to get him going in the ground ambulance and either pick him up en route or drive him all the way; I don't know how much waiting for our arrival delayed his arrival in the hospital.