Types of Sleep Studies
The following are the various types of sleep studies. Your doctor may prescribe one or more of these to determine how best to treat your sleep disorder.
Nocturnal Polysomnogram, NPSG – The standard overnight diagnostic sleep study used to assess sleep disorders, including sleep apnea, periodic limb movement disorders, insomnia, 24 hour sleep-wake cycle disruptions etc. The study includes various physiological measurements such as respiratory effort and airflow, EEG (brain waves), EKG (Heart), EMG (muscle movement), oxygen saturations, and snoring. These parameters are standard on every overnight sleep study both diagnostic and therapeutic.
Continuous Positive Airway Pressure, CPAP Titration – A therapeutic study used to treat obstructive sleep apnea syndrome (OSAS). The purpose of this study is to explore a variety of CPAP pressures to determine which is the most effective in eliminating apneic events and snoring.
Split Study – A sleep study which combines a 2 – 4 hour diagnostic test and a therapeutic test in the same night. This study is possible for every adult so that patients with severe OSAS may be treated immediately. If a patient is not “split” to CPAP then the study is run as a NPSG. The patient may return for a full night of CPAP if the diagnostic test finds evidence of sleep apnea and treatment is advised.
Bi-Level Titration – An alternate therapeutic study used to treat patients that have very high severe obstructive sleep apnea syndrome or those that are intolerant of CPAP. Pressures are explored on the inhalation and an alternate pressure on exhalation. This pressure spread is used to ease the work of breathing.
REM Behavior Disorder, RBD – a modified NPSG with electrodes added to the arms (in addition to the legs) to determine the presence of movement during REM, a stage of sleep during which the muscles are immobile. This study is performed if a patient is suspected of acting out his/her dreams at night.
NPSG with End Tidal CO2 – a modified NPSG with the use of end tidal CO2 monitoring. This is a useful adjunct to the airway recording to assist in the detection of obesity hypoventilation and Hypercapnia, or CO2 retention. ETCO2 recording is considered the gold standard for pediatric polysomnography.
Expanded EEG Sleep Recording – An NPSG performed with a full EEG montage during recording. This study is used to detect the presence of nocturnal seizures in addition to other sleep disorders.
Multiple Sleep Latency Test, MSLT – A study performed during the day after a full diagnostic NPSG, this study is used to objectively determine a patient’s level of sleepiness after a night’s sleep. The MSLT is a series of five timed test, two hours apart, during which we look to see whether a patient falls asleep, how quickly, and to what stage of sleep the patient reaches. The MSLT is most commonly used to diagnose narcolepsy or some degree of excessive daytime sleepiness.
Maintenance of Wakefulness Test, MWT – A study performed to determine whether a patient is able to remain awake in a sleep induced environment. The MWT is used to assess the efficacy of the treatment of a sleep disorder.