I remember hearing that Umberto stopped his breath hold after 20 min or so, not because he couldn't keep on going, but because he was afraid of what he might be doing to his body.
Reminds me of when Cousteau started diving with the first prototype SCUBA tanks and everyone was getting bent and no one knew what was happening. "Gee, Jean-Luc, you look kinda funny... you alright?"
I'll leave the 02 experiments to someone else, thanks.
Pete
