Sleep Studies
There are several types of sleep study. The primary and most commonly done study is a Polysomnogram. This is usually done during a full night's sleep. During a sleep study, a number of physiologic variables are recorded. This usually includes 4 or more channels of EEG, a recording of air flow from the nose and mouth, an oxygen monitor on the finger, EKG, belts that record movement of the chest and abdomen, muscle activity around the chin and the lower leg. These monitoring electrodes and transducers are placed by a polysomnography technician (sleep tech). This is a painless process that takes 30 - 45 minutes in a cooperative adult and may take much longer in a child. Once the wires are in place, the patient is requested to turn out the lights and try to fall asleep. Once asleep, all the data is recorded by a computer for later analysis.

A Titration Study is a full night polysomnogram that is done in patients who have sleep apnea. During a titration study, the patient is started on CPAP and the pressure is adjusted until normal breathing resumes. The patient may also be tried on BiPAP. Another form of titration study is a Split Night Study. Some patients with severe sleep apnea can be proven to have significant problems with breathing after only 2 or 3 hours of sleep. In that case, the sleep study may be stopped and then restarted with CPAP. In other words the study is split between a typical polysomnogram and a titration study.

A Multiple Sleep Latency Test (MSLT) is also known as a nap study. This is done to document daytime sleepiness, typically in a patient thought to have Narcolepsy. This is usually started in the morning after an overnight sleep study. The patient has a number of recording electrodes but it differs from an overnight study in that air flow, rib belts, abdominal belts, EKG and oxygen are not recorded. The patient is asked to take a 20 minute nap every 2 hours through the day starting at 8:00 a.m. usually. There will be 5 naps. The primary measures are the average length of time to fall asleep in the naps (less than 10 minutes is considered abnormal) and the presence of REM. Excessive REM sleep is seen with Narcolepsy (REM sleep in 2 or more of the naps). REM sleep normally is present in at most one nap during an MSLT.