Do dogs have Asthma?

I wonder if anyone else has a Dog that does this, Because it kinda freaks me out sometimes... Butterfly will start to breath funny as if she is having a asthma attack.. it always last about five minutes, and when it stops she seems fine... I guess it kinda looks like a Cat with a Furball, Anyway, it is weird, and she has done it for years, But i am curious if other Dogs do this, and if it is Normal, and maybe even why they do it? I figure this would be the best place to ask

Thanks,
Shell