Relationship between Apneas and REM Sleep

I am relatively new to my APAP machine. I recently had a sleep study that resulted in my APAP machine being set to a constant pressure of 9.

My apneas the last two weeks have averaged 9 per hour. Even when I have as few as 4 apneas per hour, my REM sleep is virtually nonexistent.

I measure my REM via my Apple Watch. Just to prove that my Apple Watch Sleep App is accurate, I sometimes have my wife wear it when sleeping and she frequently gets well over an hour of REM.

Does anyone know what the relationship between Apneas and REM sleep is?

Do other people fail to get REM sleep even with controlled Apneas?

Does anyone have suggestions how to get more REM sleep?

Thank you very much from this newbie

Your Apple watch may not be measuring Rem sleep accurately.