1. Don’t sedate the dog, because even though he is not considered snubbed-nosed, it will make him more – not less – anxious in the air. Trust me on this one, you want him in control of his bodily functions.

2. You can take him into the ladies’ or men’s room to go potty in the airport, no one will care, just don’t let him out of the carrier until you get him into the bathroom. Go into the handicap stall and put the newspaper down and voila, instant bathroom for dogs. Keep him on his leash obviously and this is a good time to get water into him, remember airplanes dehydrate you and your dog!

3. Be as nice as you can to people and explain that he is stressed and can not be touched, so he won’t want to growl or bark

4. Only feed him small amounts for the days leading up to your flight and try to keep him on a reasonable schedule for the flight as far as feeding and walks go, and take him for a run before you get to the airport so he is somewhat tired for the first leg of the trip
References :
travel alot internationally with dogs

They won’t take sedated animals, for the specific reason you stated quite correctly. It has to do with a short nasal passages, Persian cats also have a problem with that. Again, since it’s a long flight (which with a pet you may be forced to break into two parts and arrange a vet to check them at the stop-over airport, sometimes at your own cost, it differs from airline to airline..

Check the dimensions and other details of the carrier you are allowed in-cabin with the airliner.
Check their policy about lay-over walks, some don’t allow it for fear of carrying diseases in, and mostly don’t have vets there to check the animals and accompanying paperwork for shots, etc.

As for the breathing problems, I suggest finding out from international pet movers, they normally have those details on hand. Good luck, and good on you for not leaving your pet behind.
References :
I had to check all this when I took my cat 5500km to where we live now.