Without question, this is worth an ER vet visit. I have a few golden rules I always try to follow when making over the internet recommendations when to get to an ER vet.
Some of the examples include:
1. Any type of tremor, shaking, shivering
2. Any type of irregular breathing, excessive panting, or labored breathing
3. Any acute onset of swelling anywhere in the body
4. Irregular bleeding from mouth, nose, in the stool
So, difficult or labored breathing can be quite serious. It could suggest severe nausea, pain, heart disease, primary lung disease, as a few concerns.
Wish I could do more. Worth the ER trip.