Thank you for the additional information.
I am sorry to hear that she has been breathing differently since the trauma occurred. This is concerning since she is so young. Without examining her, giving you an exact diagnosis is going to be difficult though I can tell you some of the more common disorders that could be causing her breathing changes:
- A rib fracture which could be pushing on one of her lungs
- A chest contusion or bruise to a lung or the muscles around the ribs which could be mild or fairly deep if she was caught at an awkward angle by the chair
- An injury to her diaphragm such as a hernia causing her to not be able to expand her diaphragm fully
At this point, any breathing change really should be evaluated by a vet therefore I honestly would recommend an exam for her if at all possible. Pain is another possible cause of her signs as this can cause dogs to rotate from rapid to shallow breathing. She may need an anti-inflammatory medication such as Rimadyl or Metacam or even a mild narcotic type drug such as Tramadol to give her some pain relief which the vet can prescribe. An x-ray also is worth considering to make sure her diaphragm is intact and she does not have any rib fractures.
If you absolutely cannot get her to a vet tonight you could consider an over the counter pain medication such as aspirin, though this honestly should only be given after an exam is performed. The dose is 5 mg per pound every 12 hours. While usually safe in puppies, this medication can potentially cause an upset stomach therefore if any vomiting or diarrhea is seen I would stop the aspirin.
Hope this helps to answer your question - if not or if you have any more questions please feel free to reply. Thank you for your question.