Sneezing or Gurgling are not signs of asthma.
Asthma is an inflammatory disease. So the tubes the air travel in a sense will tighten making it more difficult to breathe. Its like taking a deep breath through your mouth, then trying to take that same breath through a tiny straw.
You may notice wheezing, "coughing", shortness of breath, increased rapid shallow breathing so increased work of breathing.
You may actually be surprised at how well your rabbit can and will tolerate one of these masks. Especially if put into a bunny burrito (a proper one) prior to putting the mask on the face, there likely wont be a whole lot of fight.
We just had to do one of these masks for our spastic border collie with chronic lung disease and he spazzed a bit the first 2 or so times but now takes it like a champ.
THe masks are too expensive. Shop around. You may be able to purchase the tube you spray the inhaler in elsewhere or from a human pharmacy and the bunny specific mask directly from the vet.