I suspect you might be able to derive a partial answer by analyzing some of the data provided by a pulse oximeter. I'll also bet you could get a better informed answer to your question if you could pull Dean Fellabaum(an MD) away from his lovefest with Rog and Timothy over in Chaff. Ditto John P (Shannon? also an MD) last sighted in the Ciprofloxacin thread.
My 2 cents: Stick with the 1000' rule of thumb and listen closely to what your body is telling you-it's got a pulse oximeter hard wired into the system. You may well find that you can exceed the 1000' ROT as you gain more experience. Only time will tell.