Wake up Desert Flower.
OK smartarse, so I posted that before I read further. But have you ever heard someone who is hypoxic? If you have, then you would know that they are indeed the signs/symptoms. Back in the days of FS in Leigh Creek, one of the guys on duty recognised the signs in the pilot of a C172 coming in from Broken Hill, & directed him to descend to a lower level.
DF.