Polysomnography (PSG) is a comprehensive, multi-parameter diagnostic test used to study and evaluate sleep disorders. Often referred to as a sleep study, polysomnography records various physiological functions during sleep, helping clinicians understand sleep patterns, detect abnormalities, and diagnose a wide range of sleep-related conditions.
What is Polysomnography?
Polysomnography is a non-invasive overnight test typically conducted in a specialized sleep laboratory or, increasingly, with portable equipment at home. During the test, multiple sensors are attached to the patient’s body to sonno monitor brain waves (EEG), eye movements (EOG), muscle activity (EMG), heart rate (ECG), respiratory airflow, blood oxygen levels, and limb movements.
These measurements collectively provide a detailed picture of the sleep architecture, including different sleep stages (REM and non-REM), respiratory effort, and any disruptions that might occur. The test is critical for diagnosing conditions such as obstructive sleep apnea (OSA), narcolepsy, restless legs syndrome, periodic limb movement disorder, and parasomnias like sleepwalking or night terrors.
How is Polysomnography Conducted?
Patients undergoing polysomnography arrive at the sleep center in the evening and prepare for the test by having electrodes and sensors attached to their scalp, face, chest, and limbs. These electrodes capture electrical signals related to brain activity, eye movement, and muscle tone.
Respiratory sensors are placed around the chest and abdomen to monitor breathing effort, and a nasal cannula or thermistor measures airflow. A pulse oximeter clipped to the finger measures oxygen saturation in the blood. Additionally, audio and video recordings may be used to capture snoring sounds or physical movements during sleep.
Once connected, the patient is encouraged to sleep normally while the sensors record data throughout the night. A trained sleep technician monitors the data in real-time from an adjacent room to ensure quality and troubleshoot any sensor issues.
Importance of Polysomnography
Polysomnography is the gold standard for diagnosing many sleep disorders. For example, obstructive sleep apnea is characterized by repetitive episodes of upper airway obstruction during sleep, leading to breathing pauses, oxygen desaturation, and fragmented sleep. PSG can precisely detect these apneas and hypopneas, assess their severity, and guide treatment decisions such as the need for continuous positive airway pressure (CPAP) therapy.
Beyond apnea, PSG helps evaluate unexplained daytime sleepiness, abnormal movements during sleep, and complex neurological conditions affecting sleep. The detailed analysis of sleep stages and architecture also provides insights into disorders like insomnia and REM sleep behavior disorder.
Advancements and Variations
While traditional polysomnography is conducted in specialized labs, advances in technology have enabled home-based PSG studies. These portable devices provide convenience and greater accessibility while still capturing critical data, although some parameters might be limited compared to in-lab studies.
Further, split-night studies combine diagnostic and treatment phases in a single night, allowing immediate titration of therapies like CPAP for sleep apnea, optimizing patient care and reducing diagnostic delays.
Polysomnography remains an essential tool in sleep medicine, providing a window into the complex physiology of sleep. Its detailed and multi-faceted recordings enable accurate diagnosis and personalized treatment of a wide spectrum of sleep disorders, ultimately improving patients’ quality of life and overall health. If you experience symptoms such as chronic snoring, excessive daytime sleepiness, or restless nights, consulting a sleep specialist and undergoing polysomnography might be a crucial step toward restful, healthy sleep.