I have a question regarding Nitrox vs Air and how it makes you feel. After the first morning dive in Cozumel last Friday, I had a horrible headache (that I'd had from the night before but a little less pronounced before the dive) and I had gotten a bit motion sick floating on the surface after the dive. Bottom depth was around 80-85 FSW and dive time was roughly 45 minutes or so on air. I felt bad enough after that I opted not to make the second dive that morning, instead sitting on the boat and trying to relax as best I could with the pitching and rolling, which was fairly normal. After getting back to shore I talked to the dive operator and explained that I'd called my 2nd dive due to a serious headache (which was at that point near migraine status) and it was explained to me that I should've switched to Nitrox because the increased O2 in the mix (the average of all tanks tested was 30%) would actually help ease my headache and make me feel a bit better. It sounded like it made sense but without having tested it, I don't know if it would've worked or not. So is there any truth to that? Would diving EAN actually help with a headache due to the increased O2 content?
And to keep this on topic....I have noticed no decrease in tiredness from diving EAN vs Air over multiple dives.