Yes, I believe being flat could cause. I don't let them do that as I get dizzy. And I do not sleep flat because of sleep apnea. My sister who also has sleep apnea and used one of those horrible snorkels as I call the for years, if she sleeps in a recliner she has no problem. In response to her story, I have now slept for years slanted up on pillows and have no problem. I tried one night to not have them a little lower, and that night woke up gasping. It beats the snorkel for me to sleep propped up.