I don't know for sure if it is an RI or not, but if that is the only symptom and it is an RI then you have probably caught the RI early on which should make it easier to treat (I think). I do know that my BP used to make a slight sound when he was breathing but I never thought anything of it because he had no other symptoms and the vet has never found any issues with him since we got him other than times where he wasn't drinking his water and was a bit dehydrated or a situation we had where he didn't eat for a ridiculous amount of time. To calm your anxiety and make absolutely sure, then take your snake to the vet just like you're doing. I don't know how often or how many shots will have to be given, so the vets ability to give the shots might vary... Again I don't have experience with treating a snake with RI so I don't know much about the shots or vet treatments. If the vet is unable to then could someone else in your family help you? Or maybe if you mention it to the vet they will have some way to help you with it or at least give advice.