Nocturnal, laboratory-based polysomnography (PSG), also known as a sleep study, is the most commonly used test in the diagnosis of obstructive sleep apnea syndrome (OSAS). A sleep study can be used for diagnosing other sleep disorders as well, including periodic limb movement disorder, narcolepsy, chronic insomnia, and REM sleep behavior disorder. It is often considered the criterion standard for diagnosing OSAS, determining the severity of the disease, and evaluating various other sleep disorders that can exist with or without OSAS. PSG is non-invasive and consists of a simultaneous recording of multiple physiologic parameters related to sleep and wakefulness. See the image below. Home-based, limited-channel sleep studies
are being used more often to diagnosis obstructive sleep apnea, but they have some limitations.