This struck as I was going to bed tonight... it stewed to the point that I had to come write it down.
I'd recently read an account of two strong climbers that had been pinned down by wind at 14,000ft. One was tragically claimed by HACE while they waited out the winds. It stuck me as odd that they he had done so well over two strenuous days, only to have it hit suddenly while stationary and a somewhat mild altitude.
I moonlight in motorsport, and have taken an interest in aerodynamics over the years. Oversimplified; the area on the leading edge (windward) of a surface experiences high pressure, the area on the trailing edge (leeward) experiences low pressure. The air density in areas protected form the wind is lower.
At altitude, it's not that there is less O2 in the air, there is less of everything, less air altogether. The pressure drops as you distance yourself from the earths core, hence the popping of ears while flying.
When you are pinned down by wind, and you seek shelter in the on the leeward side of a rock or ridge, the localized pressure in that area is lower than it is on the windward side. By how much depends on the speed of the wind: The higher the wind, the lower the pressure.... and the less air density you have. Being pinned down implies wind of excessive speed, has anyone ever mention the pressure differentials?
Could the low pressure area on the leeward side of rock in a wind storm produce O2 levels lower than would be expected for a given altitude?