I Have wondered if it is heat/salt related. She has been doing it since she was 3 days old and it does not seem to change with weather, we do live in a very hot climate, but even in the winter she vomits alot. We have been keeping track for the last month and it is every 3 days. Prior to that it was more random. The GI who we see is one of the best in the country and she has had every test he can think of including and endoscopy and gastric emptying study. Her reflux is controlled and her enzymes are fine, so it is not either of those things.
Ratotosk, I had the exact same thing happen this weekend as you did. We were driving, she looked at me and said her tummy hurt and then vanilla milkshake all over the back seat, car seat and clothes. I was stuck in traffic and there was not a thing I could do. Yuck!!! As soon as she threw up she was fine and crying for food. Kept it down just fine the second time.
I really think the vomiting is some wierd CF related thing, that is why I was wondering if other people have the same issue.