airway

This condition already involves pauses in breathing, and back sleeping can increase the likelihood that the airway collapses completely, blocking airflow.

For some people, lying on their back can cause the soft tissues of the throat and tongue to collapse into the airway.

I mean, your tongue has that flexibility in your mouth, 'l', but you can’t close your airway like you’re making a figure 8 out of a straw, and keep the air going round the sides.