Last night at 1 a.m. my dog sounded like she was heaving. She had labored breathing that sounded like she couldn't catch her breath. She's done this other times for no reason at all. She's been downstairs just lying around & it happens. Yet she'll go racing outside later after she has had these spasms like nothing's wrong with her. I pat her firmly on her back to try and get her to stop and this either seems to do the job or she's just stopped on her own. One particular thing doesn't trigger this. Should I be exceptionally concerned? My vet doesn't seem to know what I'm talking about & it's just like a car...when you take it in...it doesn't make the noise. Can you help?