I have these same sudden attacks and I have found that as soon as you feel one coming on is to take 3 or 4 chew able baby aspirin and lots of water. It stops the intense part of the pain pretty fast. If I do nothing they can last a long time with severe pain. I have a bad back and I am finding these seem to come on after walking crooked for a while which might give some validity to the person mentioning rib cage misalignment.