Nitrox & high altitude question

[MgicTwnger]

Recently the Discovery channel had a show which featured three divers going into a small lake inside a glacier on the side of the higest peak of the Alps, Mt. Blanc. I'm not sure of the altitude, but it was way up there. The dive itself went to about 80', water temp was actually -1C, just below freezing.
As best I could make out they were using Nitrox with the O2 at better than 50%. The reason was something about avoiding DCS.
That's about all I could figure out, since the guy translating sounded like Inspector Clouseau with a head cold.
What I'm wondering is did I get this info right and if so, why the 50%+ mix?

[reefraff]

I didn't see the show but without getting into a generic discussion about the effects of EAN diving and the longer NDL's it affords, I suspect that you aren't adjusting the baseline atmospheric pressure to compensate for the altitude and the water pressure to compensate for the fresh water:

A dive from sea level to 80fsw on EAN50 is kind of scary -

((80/33)+1.0=3.42).50=1.71ppO2

A dive from 8000 feet to 80ffw on EAN50 looks a whole lot better, however -

((80/34)+.75=3.11).50=1.55ppO2

I pulled 8000 feet altitude out of my keister (and because it works out to .75ata) but Mont Blanc is a big mountain and I don't think you'll find glaciers at 5000 feet in the Alps. You still need to worry about OxTox and the clock at altitude but you would also need to be dealing with the fact that EAN21 would probably leave you short of breath and working too hard and the standard therapy for that (ask the mountain climbers and skiers) is supplemental oxygen. I'd say offhand that these guys were probably using an acceptable mix, given their circumstances.