Institute of Sleep Medicine - What is Sleep Apnea?

What is Sleep Apnea?

Sleep Apnea is a condition in which a person stops breathing during sleep. In Greek mythology this condition was referred to as Ondine's curse. Today, we know that there are two forms of Sleep Apnea.

A Central Apnea is a situation in which the stimulation from the Central Nervous System to the muscles of respiration is interrupted for a period of time and is considered serious when these periods last longer than ten seconds and result in disruption of sleep. Obstructive Sleep Apnea is a situation, which results from a physiologic change that occurs in everyone, namely decreased muscle tone. This phenomenon is due to the decreased electrical output from the central nervous system that occurs at sleep onset.

The tongue, pharyngeal walls, uvula, and soft palate are all skeletal muscles. At sleep onset the muscles become floppy and begin to collapse into the airway. Snoring begins. Snoring is the sound produced by the vibration of tissues in the oro-pharynx (throat) as air passes over the floppy tissues. As the tissues continue to collapse into the airways, partial obstruction of airflow (hypopnea) can develop. Frequently, the collapse will progress to the point of total airway obstruction (apnea).

What is a Sleep Test?

A sleep test is performed in a controlled environment where a person will come to spend at least ten hours of the day or night, depending upon his or her normal sleep schedule. He or she is asked to stay in a quiet, dark bedroom with electrodes attached to different areas of the body so that the technicians can monitor what happens during sleep. The standard sleep test requires that the patient have electrodes attached to top and rear of the head to determine the level of consciousness he or she is in at all times during the study. An electrode is placed above the right eye and below the left eye to monitor eye movement with two electrodes on the chin to gauge muscle tone.

A small device on the upper lip measures airflow from both the nose and mouth. The effort to move air into the airway is determined by having an expandable belt attached to the chest and stomach.

Heart activity is monitored by a two lead EKG, while the oxygen level and pulse are determined by placing a probe over one of the fingernails.

A person's sleep can also be disturbed by regular movement of the arms and legs so electrodes are placed on each arm and leg to pick up the amount of movement that occurs in those areas, too.

Physicians, who are Sleep Specialists, can learn a great deal about a patient's medical condition during this test. In over fifty percent of the patients tested nation wide, a Sleep Specialist can determine a course of therapy for the patient after one night of testing. At Staten Island University Hospital's Institute of Sleep Medicine, seventy-five percent of the patients have a course of therapy offered to them after one night of testing.

In addition to the standard sleep test, most sleep labs will offer "Nap Studies" or Multiple Sleep Latency Tests, too. This is a study performed immediately after a full night sleep study in which the patient slept without interruption from apnea or movement of the extremities of the body. Five, twenty minute naps are scheduled to see how long it takes the person to fall asleep and to determine if the person can have a period of Rapid Eye Movement (REM) within fifteen minutes after falling asleep. If the person falls asleep in five minutes or less and has at least two periods of REM during the five naps, he or she quite likely is suffering from Narcolepsy