I just love google and wikipedia. I've learned something important that I had no idea I should know about. I'm trying to find ways to increase your blood oxygen level. Apparently hyperventilation is not really one of them. It appears that all those breath holding games we played as kids were in a way playing with fire as it increase your tolerance of CO2 without increasing your O2 level. Yikes - glad I didn't know this when I was depressed and semi-suicidal.
What started this is that I'm wondering if there's any connection to water drinking and blood O2 levels. In other words I'm wondering if the O in H2O crosses over to the blood - not likely, but worth checking.