Good evening - I'm Dr. Sara. I'm a licensed veterinarian who works exclusively with cats and dogs. I'm sorry to hear that Maggie is having a rough night.
With dogs who have chronic respiratory issues, any change in respiratory effort or rate merits a call to the vet. Putting a fan on her is a great idea, and I typically recommend this for my clients in my own practice. Unfortunately this could be something as simple as a bit of anxiety due to changes in her daily routine all the way up to something really serious like a decompensation of her respiratory disease or a worsening of her blood pressure issues.
If we consider stress/anxiety, there are some great calming treats on the market that can take the edge off - my favorite is one called Composure Pro that contains Thiamine, L-theanine, and colostrum calming complex. There is a GNC version with the same active ingredients available at PetSmart.
You could also consider giving the tramadol at the maximum labelled dose and frequency. Often this drug is prescribed with a flexible label saying something like "up to every X number of hours as needed" in which case I'd consider giving the maximum dose allowed by the label.
Many cancers can also spread to the lungs, causing increased respiratory effort and sometimes coughing. Unfortunately if that's the case, there's probably not much more than can be done to help aside from maybe considering a course of steroids as a "last ditch" effort. This sort of metastasis is typically evident on a chest radiograph.
Check to be sure that her gums are bubble gum pink - if they are pale, white, or yellow, you should seek ER care. Also, I would check a rectal temperature and consider ER care if her temp is over 103.
Please let me know what follow up questions I can answer!