What types of tests are done in a sleep study and what do they test for?
An in-lab sleep study — or polysomnogram (PSG) — is a comprehensive test used to disagnosis 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 in-lab sleep studies are:
- Diagnostic (routine) overnight PSG — This is the general monitoring of sleep architecture (such as the amount of NREM and REM sleep, number of arousals) and body functions during sleep, including breathing patterns, heart rhythms, and limb movements. It is usually performed when evaluating sleep-related breathing disorders or abnormal movements during sleep.
- Positive Airway Pressure (PAP) titration — PAP therapy 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 PAP setting required to alleviate sleep apnea.
- Split-night PSG with PAP 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 PAP therapy.
- 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 includes:
- 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 rapid eye movement (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.
Home Sleep Testing (HST):
This is a modified type of sleep study that can be done in the comfort of home. It records fewer body functions than PSG, including airflow, breathing effort, blood oxygen levels and snoring to confirm a diagnosis of moderate to severe obstructive sleep apnea. It is not appropriate to be used as a screening tool for patients without symptoms. It is not used for patients with significant medical problems (such as heart failure, moderate to severe cardiac disease, neuromuscular disease, or moderate to severe pulmonary disease). It is also not used for patients who have other sleep disorders (such as central sleep apnea, restless legs syndrome, insomnia, circadian rhythm disorders, parasomnias, or narcolepsy) in addition to the suspected obstructive sleep apnea.