To be blunt, the couple of 'absolutes' I have seen in this thread are a bit disheartening. With just a quick search 02 is effective at total or partial aborts for 70-80% of patients, there are still patients, such as me, who get little to no relief from any flow rate of 100% o2. As for imitrex, it was 100% effective for me, for about 6 months, then I began getting 1 in 4 times that it failed to do anything, up to a point when it was about 2-3 in 4 that failed to work, so with the associated cost, other considerations I stopped using them.
I am a refractory chronic ch sufferer with 5+ attacks daily, from all the other reading here I have seen many many variation in efficacy to treatments, to suggest if one thing does not work then you do not have this hellish thing, is a bit of a slap to those who do have this and are getting fucked because shit is never 100% with ch. Other than it 100% sucks.