I know the sound of a kitty with a respiratory infection well - it's a haunting sound. I'm sorry you have to hear it, and sorrier for poor Poppaea! I do not have groundbreaking suggestions, however. Pinot had a severe one with a viral disease when we first got her. The emergency vet had her for about 8 hours on IV fluid and meds which did a world of good. She wasn't completely cured, but it put her on the path. Those things take a bit of time to completely kick. {{{hugs}}}