A sleep study or polysomnogram (PSG) is a test that electronically transmits and records specific physical activities while you sleep. The recordings become data that a qualified sleep specialist analyzes to figure out if you have a sleep disorder.
There are four kinds of sleep studies.
Diagnostic daytime multiple sleep latency test (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's performed on the morning following a diagnostic overnight PSG.
Two-night evaluation PSG and CPAP titration. On the first night, you'll have general monitoring and diagnostic evaluation. If sleep apnea is discovered, you'll come back for a second night to determine the right air pressure for CPAP (continuous positive airway pressure) treatment. It delivers air into your airways through a specially designed nasal mask.
Split-night PSG with CPAP titration is done when moderate or severe sleep apnea 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 CPAP pressure needed to offset apnea.
What to Expect
On the night of your sleep study, you'll be assigned to a private bedroom in a sleep center or hospital. Near the bedroom will be a central monitoring area, where technicians watch and check on you while you sleep.
You'll be hooked up to equipment that may look uncomfortable. However, most people fall asleep with little difficulty.
Sticky surface electrodes will be put on your face, scalp, chest and limbs. They'll send electrical signals, which are generated by your brain and muscle activity, to the measuring equipment. While you sleep these signals are recorded digitally. These sensors record your brain activity, heart rate, heart rhythm and blood pressure.
Other Tests and Equipment
EOG (electro-oculogram) to record eye movements; these movements are important in determining the different sleep stages, particularly REM stage sleep.
Nasal airflow sensor to record airflow
Snore microphone to record snoring activity