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Sleep disorder diagnosis through a sleep study

A sleep study may be recommended for sleep problems affecting breathing, such as obstructive sleep apnoea.

A person undergoing a sleep study will stay overnight at a sleep clinic while they are wired up to special monitoring equipment.

Measurements are taken during the night of oxygen levels, breathing and chest movement.

Types of sleep study

  • Diagnostic overnight polysomnographic or PSG: general monitoring of sleep (for example, the amount of non-REM and REM sleep with the aid of brain wave and eye movement detectors, number of arousals, etc.) and a variety of body functions during sleep, including breathing patterns along with oxygen levels in the blood, heart rhythms and limb movements.
  • Diagnostic daytime multiple sleep latency test (MSLT): the MSLT is used to diagnose narcolepsy and to measure the degree of daytime sleepiness. It measures how quickly you fall asleep in quiet situations during the day. It also monitors how quickly and how often you enter REM sleep. To ensure accurate results, it is performed on the morning following a diagnostic overnight PSG.
  • Two-night evaluation PSG and CPAP titration: CPAP (continuous positive airway pressure) is a sleep apnoea treatment that involves the delivery of air into the airways through a specially designed nasal mask. On the first night, general monitoring and diagnostic evaluation is conducted. If sleep apnoea is discovered, the patient returns for a second night to determine the necessary CPAP pressure required to alleviate apnoea.
  • Split-night PSG with CPAP titration: split night PSG is conducted when moderate or severe sleep apnoea has been discovered or strongly suspected during the first part of the night’s study. The second half of the night is used to determine the necessary CPAP pressure required to alleviate apnoea.

Equipment used for a sleep study

If you have a sleep study, surface electrodes will be put on your face and scalp and 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 will be placed around your chest and abdomen to measure your breathing. An oximeter probe will be put on your finger to measure the amount of oxygen in your blood.

Other tests and equipment for a sleep study

  • EEG (electroencephalogram) to measure and record brain wave activity.
  • EMG (electromyogram) to record muscle activity such as face twitches, teeth grinding and leg movements. It also helps in determining the presence of REM stage sleep.
  • EOG (electro-oculogram) to record eye movements. These movements are important in determining the different sleep stages, particularly REM stage sleep.
  • ECG ( electrocardiogram) to record heart rate and rhythm.
  • Nasal airflow sensor to record airflow.
  • Snore microphone to record snoring.
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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on April 25, 2016

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