A sleep study — or polysomnogram (PSG) — is a multiple-component test that electronically transmits and records specific physical activities while you sleep. The recordings become data that are analyzed by a qualified doctor to determine whether or not you have a sleep disorder.
The four types of polysomnographic studies are:
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Diagnostic overnight PSG — This is the general monitoring of sleep architecture (such is the amount of NREM and REM sleep, number of arousals) and a variety of body functions during sleep, including breathing patterns, heart rhythms, and limb movements. It is usually indicated in the evaluation of sleep-related breathing disorders or abnormal movements during sleep.
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Diagnostic daytime multiple sleep latency test (MSLT) — This test is used to diagnose narcolepsy and to measure the degree of daytime sleepiness. To ensure accurate results, it is performed on the morning following a diagnostic overnight PSG.
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Two-night evaluation PSG and CPAP titration —
CPAP (continuous positive airway pressure) is a sleep apnea treatment that involves the delivery of air into airways through a specially designed nasal mask. On the first night of the two-night protocol, general monitoring, and diagnostic evaluation are conducted. If sleep apnea is discovered, the patient returns for a second night to determine the necessary CPAP pressure required to alleviate apnea.
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Split-night PSG with CPAP titration — Split night PSG is conducted when moderate or severe sleep apnea has been discovered or strongly suspected during the first part of the nights study. The second half of the night is used for CPAP titration.
What to expect
On the night of your sleep study, you will be assigned to a private bedroom in a sleep center or hospital. Near the bedroom will be a central monitoring area, where the technicians monitor sleeping patients.
You will be hooked up to equipment that might look uncomfortable. However, most patients fall asleep with little difficulty.
The equipment used in a sleep test
- Surface electrodes on your face and scalp will send recorded electrical signals to the measuring equipment. These signals, which are generated by your brain and muscle activity, are then recorded digitally.
- Belts are placed around your chest and abdomen to measure your breathing.
- A bandage-like oximeter probe on your finger is used to measure the amount of oxygen in your blood.
- An EEG (electroencephalogram) is used to measure and record brain wave activity.
- An EMG (electromyogram)
records muscle activity such as face twitches, teeth grinding, and leg movements. It also helps in determining the presence of REM stage sleep.
- An EOG (electro-oculogram) is used to
record eye movements. These movements are important in determining the different sleep stages, particularly REM stage sleep.
- An EKG (electrocardiogram) to
record heart rate and rhythm.
- A nasal airflow sensor is used to record airflow.
- A snore microphone to record snoring activity.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/21/2005
