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The word polysomnography, derived from the Greek roots "poly," meaning many, "somno," meaning sleep, and "graphy" meaning to write, refers to multiple tests performed on patients while they sleep. Polysomnography is an overnight test to evaluate sleep disorders. Polysomnography generally includes monitoring of the patient's airflow through the nose and mouth, blood pressure, electrocardiographic activity, blood oxygen level, brain wave pattern, eye movement, and the movement of respiratory muscle and limbs.


Polysomnography is used to help diagnose and evaluate a number of sleep disorders. For instance, it can help diagnose sleep apnea, a common disorder in middle-aged and elderly obese men, in which the muscles of the soft palate in the back of the throat relax and close off the airway during sleep. This may cause the person to snore loudly and gasp for air at night, and to be excessively sleepy and doze off during the day. Another syndrome often evaluated by polysomnography is narcolepsy. In narcolepsy, people have sudden attacks of sleep and/or cataplexy (temporary loss of muscle tone caused by moments of emotion, such as fear, anger, or surprise, which causes people to slump or fall over), sleep paralysis or hallucinations at the onset of sleep. Polysomnography is often used to evaluate parasomnias (abnormal behaviors or movements during sleep), such as sleep walking, talking in one's sleep, nightmares, and bedwetting. It can also be used to detect or evaluate seizures that occur in the middle of the night, when the patient and his or her family are unlikely to be aware of them.


Polysomnography is extremely safe and no special precautions need to be taken.


Polysomnography requires an overnight stay in a sleep laboratory. During this stay, while the patient sleeps, he or she is monitored in a number of ways that can provide very useful information.
One form of monitoring is electroencephalography (EEG), in which electrodes are attached to the patient's scalp in order to record his or her brain wave activity. The electroencephalograph records brain wave activity from different parts of the brain and charts them on a graph. The EEG not only helps doctors establish what stage of sleep the patient is in, but may also detect seizures.
Another form of monitoring is continuous electro-oculography (EOG), which records eye movement and is used to determine when the patient is going through a stage of sleep called rapid-eye-movement (REM) sleep. Both EEG and EOG can be helpful in determining sleep latency (the time that transpires between lights out and the onset of sleep), total sleep time, the time spent in each sleep stage, and the number of arousals from sleep.
The air flow through the patient's nose and mouth are measured by heat-sensitive devices called thermistors. This can help detect episodes of apnea (stopped breathing), or hypnopea (inadequate breathing). Another test called pulse oximetry measures the amount of oxygen in the blood, and can be used to assess the degree of oxygen starvation during episodes of hypnopea or apnea.
The electrical activity of the patient's heart is also measured on an electrocardiogram, or ECG. Electrodes are affixed to the patient's chest and they pick up electrical activity from various areas of the heart. They help detect cardiac arrythmias (abnormal heart rhythms), which may occur during periods of sleep apnea. Blood pressure is also measured: sometimes episodes of sleep apnea can dangerously elevate blood pressure.
In some cases, sleep laboratories monitor the movement of limbs during sleep. This can be helpful in detecting such sleep disorders as periodic limb movements.


The patient may be asked to discontinue taking any medications used to help him/her sleep. Before the patient goes to sleep, the technician hooks him or her up to all of the monitors being used.


Once the test is over, the monitors are detached from the patient. No special measures need to be taken after polysomnography.

Normal results

A normal result in polysomnography shows normal results for all parameters (EEG, ECG, blood pressure, eye movement, air flow, pulse oximetry, etc.) monitored throughout all stages of sleep.

Abnormal results

Polysomnography may yield a number of abnormal results, indicating a number of potential disorders. For instance, abnormal transitions in and out of various stages of sleep, as documented by the EEG and the EOG, may be a sign of narcolepsy. Reduced air flow through the nose and mouth, along with a fall in oxygenation of the blood, may indicate apnea or hypopnea. If apnea is accompanied by abnormalities in ECG or elevations in blood pressure, this can indicate that sleep apnea may be particularly harmful. Frequent movement of limbs may indicate a sleep disorder called periodic limb movement.



National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. http://www.nhlbi.nih.gov.


the polygraphic recording during sleep of multiple physiological variables that are directly or indirectly related to the state and stages of sleep; done to assess possible biological causes of sleep disorders.


A sleep study that measures multiple physiologic variables associated with sleep. Includes oxygen saturation, electrocardiography, air flow, respiratory effort, limb movement, eye and jaw muscle movement, and brain electrical activity.


/poly·som·nog·ra·phy/ (pol″e-som-nog´rah-fe) the polygraphic recording during sleep of multiple physiologic variables related to the state and stages of sleep to assess possible biological causes of sleep disorders.


Etymology: Gk, polys, many + L, somnus, sleep + Gk, graphein, to write or record
the polygraphic recording during sleep of multiple physiological variables, both directly and indirectly related to the state and stages of sleep, to assess possible biological causes of sleep disorders.


Cardiopulmonary sleep study, sleep apnea study Sleep disorders The continuous and simultaneous recording of multiple physiological variables during sleep–ie, EEG, EOG, EMG–the 3 basic stage scoring parameters, EKG, respiratory air flow, respiratory excursions, lower limb movement, and other electrophysiologic variables, and electrooculography; a polysomnograph uses noninvasive sensors for nasal airflow–thermocouple, oral airflow–end-tidal CO2 gauge, tracheal sounds–microphone, thoracic and abdominal respiratory effort–inductance plethysmography, oxyhemoglobin–finger-pulse oximeter Indications Monitor defects in respiratory control–sleep apnea disorders, COPD, restrictive ventilatory disorders


Simultaneous and continuous monitoring of relevant normal and abnormal physiologic activity during sleep.
[poly- + L. somnus, sleep, + G. graphō, to write]


The simultaneous monitoring, during sleep, of a number of parameters in a patient. These include electroencephalogram, electrocardiogram, electromyogram, rapid eye movements, chest excursion, mouth and nose air entry rates, blood oxygen saturation and the frequency and loudness of snoring.

Patient discussion about polysomnography

Q. Could someone please explain about the Fibromyalgia and sleep studies? My cousin who is 15 yrs old is suffering from sleep related problems. Should I suspect that he have fibromyalgia syndrome? Could someone please explain about the Fibromyalgia and sleep studies?

A. You could have given more details about your cousin’s sleep related problem. I could not say anything directly for your cousin as I don’t know about his actual problem. But generally saying, Individuals who have been diagnosed with fibromyalgia/who suspect they have fibromyalgia syndrome, sometimes submit themselves to sleep studies. Sleep studies can provide confirmation of a patient's sleep related problems by monitoring brain wave activity. By monitoring such neural activity, information can be gleaned regarding the quality and nature of sleep that a fibromyalgia patient experiences. Recent evidence indicates that fibromyalgia may be related to insufficient amounts of deep level delta wave sleep. Delta wave sleep is the level of sleep at which a person's body both recuperates and regenerates. Failure to reach or maintain deep level sleep may have something to do with the pain that is experienced by those who have fibromyalgia.

More discussions about polysomnography
References in periodicals archive ?
Demographic and polysomnographic characteristics of the study group were consistent with the literature (27,28,29,30).
Although a polysomnographic analysis would yield much more precise and valid results, it would be highly impractical in everyday practice.
Clinical and polysomnographic characteristics of 34 patients with Kleine-Levin syndrome.
Polysomnographic data suggests an increase in Stage Wake and Stage I plus frequent periodic limb movements during sleep.
Clinical and polysomnographic features of a large Turkish pedigree with restless leg syndrome and periodic limb movements.
Polysomnographic variables after 1-month follow-up were further analyzed as below.
Sleep problems in ankylosing spondylitis: Polysomnographic pattern and disease related variables.
automated analysis of polysomnographic recordings in patients with chronic obstructive pulmonary disease.
Examination of polysomnographic data collected on patients with ADHD prior to and during use of zolpidem, as well as during use of any subsequent sleep medication, would provide objective data for accurately assessing quality and quantity of sleep.
Terzano, "Distinctive polysomnographic traits in nocturnal frontal lobe epilepsy," Epilepsia, 53, 2012, 1178-1184.
12) All these trials included subjective sleep measures and all except for the long-term safety study also incorporated polysomnographic assessment.
A comparison of the parents' questionnaire scores with their children's apnea-hypopnea index obtained during a subsequent overnight polysomnographic study found that the screen had a 78% sensitivity for mild to severe OSA cases, with a 40% specificity.