Sleep Studies

Also known as polysomnography, sleep studies are tests used to help in the differential diagnosis of sleep disordered breathing. Several parameters are evaluated for the patient being tested for sleep disorder; these include cardiac rate and rhythm, chest and abdominal wall movement, nasal and oral airflow, oxygen saturation, muscle activity, retinal function, and brain activity during the sleep phase.

Purpose

• To diagnose breathing disorders in persons with a history of excessive snoring, narcolepsy, excessive daytime sleepiness, insomnia, cardiac rhythm disorders, and restless leg spasms.

Patient Preparation

• Explain the purpose of the test to the patient and have him maintain normal sleep schedules so that he's neither deprived of sleep nor overrested.
• Inform the patient that sleep studies are usually scheduled for the evening and night hours, usually 10 p.m. to 6 a.m, and take place in a designated sleep laboratory.
• Explain to him that he should abstain from caffeinated products and naps for 2 to 3 days before the test.
• Tell him that he may bathe or shower before the test.

Procedure And Posttest Care

• Electrodes are secured to the patient's skin, depending on the type of monitoring being used.
• Ensure the patient's comfort and tell him that normal body movements won't interfere with the electrodes.
• The lights are turned off and the EEG monitored for a baseline reading before the patient falls asleep.
• Ensure that the recording and video equipment record the sleep events as they occur.
• Monitoring of the patient during sleep continues until the test is completed.

Precautions

• For the patient with known sleep apnea, split-night studies may be ordered. These include monitoring the patient for the first half of the night, then using continuous positive airway pressure or nasal ventilation to open the obstructed airway during the second half of the night.
• Monitor the patient for respiratory distress.

Normal Findings

A normal sleep study shows a respiratory disturbance index (or apneahypopnea index) of fewer than 5 to 10 episodes per study period and normal electrocardiogram (cardiac rate and rhythm), impedance (chest and abdominal wall motion), airway (nasal and oral airflow), arterial oxygen saturation (oximetry), leg electromyogram (for muscle activity), electrooculogram (for retinal function), and EEG (for brain activity).

Abnormal Findings

Abnormal recordings reveal obstructive sleep apnea syndrome. Abnormal movement during sleep indicates a seizure or movement disorder.

Interfering Factors

• Electrophysiologic artifacts, defective electrodes, diaphoresis, environmental noises
• Patient's inability to fall asleep