Thanks for all your replies - very helpful!
As I am sure you know, with pneumothorax, there is a hole in the lung which allows air to leak out of the lung and into the chest cavity.
Pneumothorax can be spontaneous (happens suddenly with no known cause, we call this idiopathic) or can be because of pathology in the lungs, or by trauma as has been the case with Noel. The prognosis largely depends on the cause, with trauma having a really good prognosis if the dog is helped to breath so that the hole can close over.
Here is more about pneumothorax:
I worked in an emergency clinic for 3 years and have seen dozens of cases of pneumothorax caused by trauma and other causes. The hole in the lungs DOES usually heal, as long as you can keep the dog able to breathe for long enough. If there is a very large hole, a chest tube is needed in order to continuously suction out the leaking air. This allows the lung to function and the body to heal. We rarely had to keep a chest tube in longer than a week!
So, although it is hard for me to give a prognosis without seeing the dog and all of her test results, I do want to tell you that I have had dozens of patients recover from pneumothorax and have no long-term complications at all. It really just depends on the cause.
Your dog's prognosis largely depends on how she does over the next week. Does the air return? How much and how fast? If it comes back quickly, a chest tube should be placed. With treatment, most dogs do recover!
I am concerned about her because she is breathing so rapidly. Dogs with pneumothorax will often develop a "barrel-like" chest as air leaks out of the lungs. They breathe rapidly and shallowly. They have difficulty lying down and try to rest propped up on furniture. As it progresses, they refuse to eat and drink as they are so short of breath it is not possible.
If Noel is reluctant to move, has a barrel like chest, is unable to lie down or is having more difficulty breathing, then I do think you should see a vet tonight. If you cannot get her to a vet tonight, I would certainly wake up at least twice in the night to check her! If the hole in her lungs is not closing, she may need a "chest tap" to remove excess air from around her lungs, which will give more room for her lungs to expand fully. A respiratory rate of over 80 is very rapid, and suggests that she does need a chest tap. I am concerned about her, and it sounds like you are too. Breathing is such a vital function that I would feel much better if you had her checked.
If this has been helpful, please "Accept" my answer and provide feedback. If you need more information, just click on reply and I will try to provide it!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would strongly advise contacting your regular veterinarian.
BEST WISHES to you and to Noel!!