Listen carefully.....You can buy rescue Oxygen with a regulator that goes up to 25L/min. At 8-15 L/min a migraine should greatly improve or go away altogether after 5 min. You have to hyperventilate. I prefer to remove the mask and inhale off the hose and exhale thru your nose. 75% of people I know that tried this have a positive response.
Life Corportation sells the oxygen.