A. The upper airway, between the nostrils and vocal cords, frequently collapses while people are sleeping. They continue to make efforts to breathe but no air can go in or out through the nose or mouth.  If they are unable to breathe for 10 seconds or longer, we say that they are having an episode of obstructive sleep apnea.  People can have many apneas during the night, sometimes as many as 30 or more  per hour of sleep.  Sleep apnea leads to poor quality sleep and daytime sleepiness. In some cases, sleep apnea can also lead to more severe problems like cardiovascular disease.