Sleep Disorders: Making the Diagnosis
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 sleep
specialist to determine whether or not you have a sleep disorder.
There are four kinds of polysomnographic studies, including:
- Diagnostic overnight PSG:
General monitoring of sleep architecture (for example, the amount of Non-REM
and REM sleep, number of arousals, etc.) and a variety of body functions
during sleep, including breathing patterns, heart rhythms and limb movements.
- Diagnostic daytime multiple sleep latency test
(MSLT): 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.
- Two-night evaluation PSG and CPAP titration: CPAP
(continuous positive airway pressure) is a sleep apnea treatment
that involves the delivery of air into the airways through a specially
designed nasal mask. On the first night of the two-night protocol, general
monitoring and diagnostic evaluation is conducted. If sleep apnea is
discovered, the patient returns for a second night to determine the necessary
CPAP pressure required to alleviate apnea.
- 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 to
determine the necessary CPAP pressure required to alleviate apnea.
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 may look uncomfortable. However, most
patients fall asleep with little difficulty.
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. A bandage-like oximeter probe will be put on your finger to measure
the amount of oxygen in your blood.
Other Tests and Equipment
- 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.
- EKG (electrocardiogram) to record heart rate and
rhythm. Nasal airflow sensor to record airflow. Snore microphone to record
Reviewed by The Sleep Medicine Center at The Cleveland Clinic.
Edited by Michael J.
, WebMD, September 2004.
Portions of this page © The Cleveland Clinic
Last Editorial Review: 6/20/2005