Your turbinoplasty (nasal concha) should have improved your breathing from an obstructive point of view. I had a turbinoplasty 2 months ago/ Aaaaahh. To have open nasal passages is great. If you have Obstructive Sleep Apnea, you sleep would be worse on your back. But, Central Sleep Apnea is different. It is a condition where the brain fails to tell the diaphragm to take a breath.

For me, my CSA was likely due to inflammation in my upper neck and brain stem that decreased blood flow causing the autonomic nervous system to dysfunction and forget to tell me to take a breath. Resolving my neck issue over time has resolved my CSA for the most part. I sleep best flat on my back with my head and neck straight.