<font face="Verdana, Arial, Helvetica" size="2">Maybe if you do a whole lot of flogging around at 10,000' in unpresurized aircraft before you get that jet job your body will be acclimatised to altitude and you'd have more useful consciousness in the even of a depressurization</font>
The adaptive changes from chronic hypoxia are usually reversible. Thus if you move from 18000' to sea level your physiology will slowly return (adapt) to its new altitude. I think some of the indigenous peoples of the Andes have a genetically higher haemoglobin concentration than 'Westerners'.
------------------
-.-- --.- -..-