Polysomnography

Polysomnography is the medical term for a sleep study. The purpose of the test is to determine what, if anything, is abnormal with a person’s sleep. In order to monitor the sleep, small metal cups connected to wires are affixed to the patient’s scalp, face and chin. These cups (called electrodes) conduct signals from the body to a series of filters and amplifiers, and a computer then displays graphic waves that represent these body signals. Technologists with years of training are able to interpret these signals to determine if you are awake, drowsy, or in dreaming or deep sleep. The signals are monitored throughout the study (which typically takes 7 to 8 hours), and the technologist (either during the study or after it is completed) will mark the sleep “stage” every thirty seconds on the recording as well as any disruptions from normal sleep.

At the same time, several different sensors monitor your breathing. A small wire or tube placed in front of the nose senses air movement, while elastic belts around the stomach and chest sense expansion, indicating breathing effort. A tiny flat microphone or vibration sensor taped to the neck detects snoring, and a plastic finger clip or wrap around the finger determines oxygen levels by measuring light absorbed by the blood vessels.

Small sticky plastic patches are placed below the shoulders and on the ribcage to monitor heart rate and rhythm (EKG). Another set of patches is placed on each of the lower legs to detect muscle twitches or foot/leg movements. All of these sensors are amplified, filtered and displayed the same as those for detecting sleep. A video camera and microphone/speaker is also installed so the technologist can observe your movements and communicate with you. The technologist will examine the signals from every one of these monitors throughout the study and mark or notate anything out of the ordinary.

(The sensors and electrodes are attached in such a manner that you can still move around, and even get up without removing everything, but it is best to ask the technologist to assist you to prevent injury or equipment damage.)

It is important to understand that a polysomnogram is a medical procedure, and you will probably not experience a completely normal night’s sleep. The technologists and physicians recognize this, and are only looking for things that are irregular – they have studied many people without sleep problems and know what is “normal” for the sleep laboratory.

Once the study is completed, the technologist will prepare a summary of the findings. A physician trained and certified in sleep medicine will then review the entire study and the technologist’s notes and summary before making a final diagnosis. This physician will also recommend treatment if any is necessary, but it is usually up to your own doctor to actually provide this treatment.

Polysomnography is almost always covered by private insurance, as long as your doctor has documented an appropriate need for testing. This might include obstructive sleep apnea, nocturnal hypoventilation (insufficient breathing), low oxygen levels at night, narcolepsy, unexplained daytime sleepiness, violent or excessive body movements while asleep, nocturnal chest pain or arrhythmias (unusual heart rhythms), or waking up choking or gasping. The procedure is usually not covered to test for insomnia, sleep talking or nightmares.