Obstructive apnea

My question is why does one have more obstructive apnea’s on their back? I’ve been on CPAP about 3 years now. I wear a full face mask. I learned early on that sleeping on my side I get the better AHI readings. In sleeping on my back I have high OSA numbers. I also feel like I can’t breathe as well and I feel pressure in my ears. Sleeping on my side I have very low OSA numbers and most nights none at all. My Hypopnea’s are normally low and the Central Apnea’s are the highest. The central’s always seem to show if I’m up and down during the night, restless, or dreaming. I’ve had Central’s in the 20’s when I have the restless nights or a lot of dreaming, usually weird dreams. Here’s a few nights of my numbers.

7/1- 7.45 hours
AHI 1.8 Central 10 OSA 0 Hypopnea 4

7/10 - 7.13 hours
AAHI 1.8 Central 11 OSA 0 Hypopnea 2

7/9 - 6.38 hours
AHI 0.6 Central 1 OSA 1 Hypopnea 1

7/8 - 6.09 hours
AHI 1.1 Central 5 OSA 0 Hypopnea 2

You have events on your back because your tongue falls back and blocks your airway - classic apnea.

Same for hypopneas. The 'centrals', or clear airway events, as you describe the times are what's called 'sleep-wake junk', not real 'central' apnea that would come in bunches throughout the night, but SWJ is just adjustment stuff prior to sleep or waking. Nothing to worry about and very common.

Thanks Julie