Unfortunately, if it's a respiratory infection then you do need vet help with it.
You can increase temperatures to the high 80s and put the water bowl on the warm side to increase the humidity - soemtimes this helps.
But ultimately, an RI is an infection. I'm not sure whether we can give any other advice than to do what your vet is advising. Maybe there's a vet tech here or someone who can tell you how your vet should be treating the snake and what drugs they should be using.