Polysomnography (PSG) is a comprehensive diagnostic tool used to study sleep and diagnose various sleep disorders. It is considered the gold standard in sleep medicine because it provides an extensive evaluation of multiple physiological parameters during sleep, helping clinicians understand the quality and architecture of sleep as well as identify abnormal events that disrupt rest.
What is Polysomnography?
Polysomnography is a multi-channel recording of several body functions during sleep. The term “poly” means many, and “somno” refers to sleep, so polysomnography literally means “many sleep measurements.” During a PSG study, various sensors sonno and electrodes are placed on the patient’s scalp, face, chest, limbs, and sometimes other parts of the body to monitor brain activity, eye movements, muscle tone, heart rhythm, breathing, oxygen levels, and limb movements.
Parameters Monitored in Polysomnography
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Electroencephalogram (EEG): Records electrical activity in the brain to determine different sleep stages (light sleep, deep sleep, REM sleep).
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Electrooculogram (EOG): Measures eye movements, crucial for detecting REM (rapid eye movement) sleep.
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Electromyogram (EMG): Tracks muscle activity, including chin and leg muscles, helping to identify muscle tone changes and periodic limb movements.
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Electrocardiogram (ECG or EKG): Monitors heart rate and rhythm throughout the night.
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Respiratory Effort: Sensors measure chest and abdominal movements to assess breathing effort.
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Airflow: Nasal and oral sensors detect airflow to identify breathing interruptions like apneas or hypopneas.
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Oxygen Saturation: Pulse oximetry measures blood oxygen levels to detect oxygen desaturation events.
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Body Position: Tracks sleeping position which can affect certain sleep disorders.
Purpose and Applications
Polysomnography is primarily used to diagnose sleep disorders such as:
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Obstructive Sleep Apnea (OSA): Characterized by repeated episodes of partial or complete blockage of the airway during sleep, leading to oxygen desaturation and frequent awakenings.
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Central Sleep Apnea: A less common disorder where breathing repeatedly stops due to lack of respiratory effort.
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Narcolepsy: A neurological condition with excessive daytime sleepiness and sudden sleep attacks; PSG helps in conjunction with multiple sleep latency tests.
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Periodic Limb Movement Disorder: Characterized by involuntary limb movements that disrupt sleep.
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REM Sleep Behavior Disorder: Patients act out their dreams during REM sleep, and PSG helps to detect abnormal muscle activity during REM.
Beyond diagnosis, polysomnography is often used to evaluate treatment effectiveness, such as after initiating continuous positive airway pressure (CPAP) therapy for sleep apnea.
The Procedure
A typical polysomnography test is conducted overnight in a sleep laboratory, where the patient arrives in the evening and sleeps while connected to the monitoring equipment. The setup involves attaching electrodes and sensors, which are non-invasive but require some preparation, such as cleaning skin and applying adhesive patches.
During the night, a sleep technologist monitors the recordings and ensures the data quality. The test usually lasts about 6 to 8 hours, covering a full night’s sleep cycle.
Advantages and Importance
Polysomnography provides objective, detailed data that cannot be captured through patient history or questionnaires alone. It helps detect hidden sleep disturbances that affect overall health, cognition, and quality of life. Untreated sleep disorders like sleep apnea have been linked to serious conditions such as hypertension, heart disease, stroke, diabetes, and depression.
Polysomnography is an invaluable tool in sleep medicine that offers a window into the complexities of human sleep. By analyzing multiple physiological signals simultaneously, it allows healthcare providers to diagnose and manage sleep disorders effectively, improving patients’ health outcomes and daytime functioning. If you or someone you know experiences persistent sleep problems like excessive daytime fatigue, loud snoring, or frequent awakenings, consulting a sleep specialist for a polysomnography study could be a critical step toward better sleep and better health.