Sleep apnea refers to repeated episodes of complete or partial blockage of the upper airways while you are sleeping. When the airways get blocked, your body and the muscles of your diaphragm and chest, work harder to pull air into your lungs.  Sleep apnea is characterized by a stopping and starting of breathing.  And this stop, start can happen up to 30 times or sometimes even more per hour. For most suffering from sleep apnea, breathing stops when the airway collapses, blocking the flow of air to and from the lungs.  This disorder is potentially serious, and can interfere with sound sleep.