Certain mechanical and structural problems in the airway cause the interruptions in breathing during sleep. Apnea occurs:
· when the throat muscles and tongue relax during sleep and partially block the opening of the airway.
· when the muscles of the soft palate at the base of the tongue and the uvula relax and sag, the airway becomes blocked, making breathing labored and noisy and even stopping it altogether.
· in obese people when an excess amount of tissue in the airway causes it to be narrowed.
· with a narrowed airway, the person continues his/her efforts to breathe, but air cannot easily flow into or out of the nose or mouth.