When the tongue is sucked completely against the back of the throat, the airway is blocked and breathing stops. Once that happens, the harder the sleeper tries to breathe, the airway becomes sealed. It’s like trying to drink through a straw that’s stuck in a lump of ice cream. The harder you suck, the flatter the straw becomes. The airway will not open until the brain’s oxygen level falls low enough to partially awaken the sleeper. The tongue then returns to a more normal position, and the airway seal is broken-usually with a loud gasp.