There is nothing that will actually dilate the trachea. The snoring does not sound like her trachea....perhaps it is something else?? Usually coughing is the biggest issue.
If the meds are helping, that is great. Be sure to keep her cool and relaxed....and her body weight normal.
There is one med that is interesting.....it worked well for one of my pups in the past. Lomotil...ask your vet about it. Here is a link so you can read a short blurb I copied from Kirk's Vet Manual. Just click on the two links on that page:
Index of /lomotil
Did your vet suggest reducing that steroid?