Dog on Tramadol: How long until side effects like rapid breathing wear off?

I have never heard of a dog being stoned on Tramadol. Tramadol usually is metabolised within 12 to 16 hours, so if this is really a case of being "stoned" then he should be out of it within 16 hours of ingesting the tablets. Sometimes Tramdol causes seizures in susceptible dogs. She could have also had an incidence of severe pain which made her breathe rapidly and shallow.
I would wait it out. Should your dog have another episode of rapid and shallow breathing, especially after the tramadol wears off, then it is likely pain that is causing this. Being a brachycephalic breed this could also be an episode of respiratory problems due to the large soft palate and narrow nares which can certainly interfere with proper breathing.