Apnea (from the Greek apnoia, meaning “not breathing”) refers to a suspension of breathing. These breathing pauses can last anywhere from a few seconds to several minutes and result in falling blood oxygen levels. Possible causes are airways that have become blocked, for example by breathing in a foreign object or by the muscles in the back of the throat relaxing during sleep and then collapsing. Several unnoticed breathing pauses during the night are a typical sign of what is called sleep apnea. Sleeping pills, alcohol or carbon dioxide can also affect particular nerve cells that make up the brain’s breathing center and impair the body’s control over breathing.