Obstructive sleep apnea (obstructive sleep apnea) is cause by the closing of the upper airway while asleep. The uvula and soft pallet collapses on the back wall of the upper airway.
Then the tongue falls backward, collapsing on the back wall of the upper airway, the uvula and soft pallet forming a tight blockage, preventing any air from entering the lungs.

The effort of the diaphragm, the chest and the abdomen only cause the blockage to seal tighter. In order to breathe the person must arouse or awaken, causing tension in the tongue thereby opening the airway, allowing air to pass into the lungs.