Polysomnography

Polysomnography (PSG) is a sleep study that records various physiological activities while a patient sleeps. The primary purpose of PSG is to diagnose and monitor sleep disorders, such as sleep apnea, insomnia, restless leg syndrome, and narcolepsy.

What happens during a Polysomnography?

During a PSG, the patient spends the night in a sleep laboratory or a hospital room. The following physiological activities are recorded:

• Brain waves: Electroencephalography (EEG) measures the electrical activity of the brain.
• Muscle activity: Electromyography (EMG) records the muscle activity, particularly in the chin and legs.
• Eye movements: Electrooculography (EOG) tracks the movements of the eyes.
• Heart rate and rhythm: Electrocardiography (ECG) monitors the heart's electrical activity.
• Breathing patterns: Respiratory effort is measured using belts around the chest and abdomen, as well as a sensor to detect airflow through the nose and mouth.
• Oxygen saturation: Pulse oximetry measures the level of oxygen in the blood.
• Body position: A sensor records the patient's body position during sleep.

Types of Polysomnography

There are several types of PSG, including:

• In-lab PSG: The most common type, where the patient sleeps in a laboratory or hospital room.
• Home sleep testing (HST): A portable device is used to record sleep data in the patient's home.
• Ambulatory PSG: A portable device records sleep data over an extended period, often several nights.

Indications for Polysomnography

PSG is typically indicated for patients with:

• Suspected sleep apnea or other breathing disorders during sleep.
• Insomnia or other sleep-wake disorders.
• Narcolepsy or excessive daytime sleepiness.
• Restless leg syndrome or periodic limb movement disorder.
• Sleep-related seizures or other neurological disorders.

Contraindications for Polysomnography

PSG may not be suitable for patients with:

• Severe claustrophobia or anxiety that would prevent them from sleeping in a laboratory setting.
• Certain medical conditions, such as severe respiratory disease, that require close monitoring and care during sleep.

Risks and Complications of Polysomnography

PSG is generally a safe procedure, but potential risks and complications include:

• Discomfort or skin irritation from the electrodes and sensors.
• Anxiety or stress related to sleeping in an unfamiliar environment.
• Potential for sleep disruption due to the monitoring equipment.

Interpretation of Polysomnography Results

The results of a PSG are interpreted by a qualified healthcare professional, typically a sleep specialist or neurologist. The interpretation includes:

• Sleep stage analysis: The percentage of time spent in different stages of sleep, including non-rapid eye movement (NREM) and rapid eye movement (REM) sleep.
• Arousals and awakenings: The number of times the patient wakes up or is aroused during sleep.
• Respiratory events: The presence and severity of breathing disorders, such as apneas or hypopneas.
• Periodic limb movements: The presence and frequency of periodic limb movements during sleep.

Limitations of Polysomnography

While PSG is a valuable diagnostic tool, it has some limitations:

• It may not capture the full range of sleep disorders or their severity.
• The results may be influenced by factors such as the patient's age, sex, and overall health.
• PSG is typically a one-night study, which may not accurately reflect the patient's typical sleep patterns.