(PSG), a type of sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine. The test result is called a polysomnogram, also abbreviated PSG.
Polysomnography is a comprehensive recording of the bio-physiological changes that occur during sleep. It is usually performed at night, when most people sleep, though some labs can accommodate shift workers and people with circadian rhythm sleep disorders and do the test at other times of day.
The PSG monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG) and heart rhythm (ECG) during sleep. After the identification of the sleep disorder sleep apnea in the 1970s, the breathing functions respiratory airflow and respiratory effort indicators were added along with peripheral pulse oximetry.
The measurements recorded during polysomnography provide a great deal of information about your sleep patterns. For example:
Brain waves and eye movements during sleep can help your health care team assess your sleep stages and identify disruptions in the stages that may occur due to sleep disorders such as narcolepsy and REM sleep behavior disorder Heart and breathing rate changes and changes in blood oxygen that are abnormal during sleep may suggest sleep apnea.Frequent leg movements that disrupt your sleep may indicate periodic limb movement disorder.
Unusual movements or behaviors during sleep may be signs of REM sleep behavior disorder or another sleep disorder.
The information gathered during polysomnography is evaluated first by a polysomnography technologist, who uses the data to chart your sleep stages and cycles. Then that information is reviewed by your sleep center doctor.
Portable monitoring (PM) may be indicated for the diagnosis of obstructive sleep apnea (OSA) in patients for whom in-laboratory PSG is not possible by virtue of immobility, safety, or critical illness. PM may also be indicated to monitor the non-CPAP treatments of sleep apnea including oral appliances, weight loss, and upper airway surgery
Multiple sleep latency testing (MSLT) is used to assess the degree of daytime sleepiness and to evaluate for possible narcolepsy. MSLT should be performed after a full-night polysomnogram to ensure that at least 6 hours of sleep precede the test and that no other causes for excessive daytime sleepiness are present