Obstructive sleep apnea is a common and serious sleep disorder that causes you to stop breathing during sleep. The airway repeatedly becomes blocked, limiting the amount of air that reaches your lungs. When this happens, you may snore loudly or making choking noises as you try to breathe. Your brain and body becomes oxygen deprived and you may wake up. This may happen a few times a night, or in more severe cases, several hundred times a night.