It's always good to get information like this! Have you also looked into the Bohr effect concerning the pH of the blood and oxygen affinity? Go on Wikipedia or there is a little bit about it on this thread
http://forums.deeperblue.net/freediv...uman-body.html. Basically if the blood is more acidic oxygen binds to haemoglobin with less affinity and so it is more easy to transport around the body, and easily deposited to the muscles that need it. Which is important in breath-holding where the blood becomes slightly more acidic due to the increasing levels of saturated carbon dioxide.
Now I have to go make some tea...
