A sleep study — or polysomnogram (PSG) — is a
comprehensive test that measures multiple parameters required for the assessment
of sleep and wake disorders. The recording is analyzed by a qualified doctor to
determine whether or not you have a sleep disorder.
The four most common types of sleep studies are:
- Diagnostic (routine) 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 performed in the
evaluation of sleep-related breathing disorders or abnormal movements during sleep.
- Split-night PSG with CPAP titration — Split night PSG is conducted
when severe sleep apnea has been discovered during the first part of the
diagnostic PSG. The second half of the night is used for administration and
titration of continuous positive airway pressure therapy (CPAP), a common treatment for sleep apnea.
- CPAP titration — CPAP is a sleep apnea treatment that
involves the delivery of air into airways through a specially designed mask.
This study is performed after a diagnosis of sleep apnea has been made on a
diagnostic PSG to determine the necessary CPAP pressure required to alleviate sleep apnea.
- 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.
What to expect
On the night of your sleep study, you will be
assigned to a private bedroom in a sleep laboratory. Near the bedroom will be a
central monitoring area, where the technologists 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
- 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. EEG (electroencephalogram)
electrodes measure and record brain wave activity. EOG (electro-oculogram)
electrodes record eye movements. These movements are important in
determining the different sleep stages, particularly REM sleep.
- EMG (electromyogram) electrodes record muscle activity from the chin
area and legs to identify abnormal movements in sleep and help in
determining the presence of REM sleep.
- A nasal-oral airflow sensor is used to record airflow through your nose and mouth.
- 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 EKG (electrocardiogram) is used to record heart rate and rhythm.
- A snore microphone records snoring activity.
- A video recording is taken to correlate movements with electrical signals.