Mike woke up because of a horrible headache early this morning. He had pulled off his o2 during the night because it was bothering his nose. It was like a band around his head at the temple level. He took an ibuprofen, drank a bottle of gatorade, put his o2 back on and I rubbed it for a while and he soon felt better and fell back asleep. I'm at work now and I keep calling him and waking him up to make sure he's ok, he feels better now. We were worried it might be CO2?? I looked it up online and couldn't find much... does anyone know the symptoms of toxicity?? We figure it may have been a migraine, brought on by the o2 falling off (he wears it every night and sporadically throughout the day) or dehydration (the gatorade helped) but CO2 scares the bejeezus out of me... any ideas?!?