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The Brody School of Medicine
Department of Internal Medicine






Sleep Disorders Center
Types of Sleep Studies
  • Diagnostic Overnight PSG (baseline)- General monitoring and evaluation.
  • Diagnostic Daytime Multiple Sleep Latency Test (MSLT) or Maintenance Wakefulness Test (MWT)- Used to diagnose Narcolepsy and measure the degree of daytime sleepiness. To ensure accurate results, it is performed on the morning following a Diagnostic Overnight PSG.
  • Two Night PSG with CPAP Titration- General monitoring and diagnostic evaluation is conducted on the first night. 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 for CPAP Titration.
CPAP Sleep Study

A CPAP Titration is required if sleep apnea is diagnosed or strongly suspected. Typically, this is a full night of study performed during a second night, but is sometimes performed during the last few hours of a split-night study.

CPAP (Continuous Positive Airway Pressure) therapy is the first line of treatment for sleep apnea. The CPAP device delivers pressurized air through tubing to a mask, which are fitted around the head with a headgear. The pressurized air acts as an airway splint. It gently opens the patient's throat and breathing passages, allowing them to breathe normally while asleep. 

During a titration study, the patient will sleep all wired up, just like a normal sleep study, but they will also wear a mask which is connected to a CPAP machine. Since the pressurized air can sometimes be irritating, the CPAP device is attached to a heated humidifier during the titration procedure. This adds moisture to the air after it leaves the CPAP and before it enters the patient's nose, easing the drying effect of the pressurized air. 

The technician will set the air pressure on the CPAP at a certain level and then observe the response of the patient. If that pressure does not reduce the number of respiratory events, or eliminate the snoring, the technician will adjust the air pressure and continue observation. This process continues throughout the night until the optimum pressure is reached.

Daytime Diagnostic Sleep Studies

A Multiple Sleep Latency Test (MSLT) or Maintenance Wakefulness Test (MWT), are designed to measure the degree of sleep tendency or sleepiness in a given patient. This test is conducted during the day following a routine PSG and features a series of up to 5 naps, each lasting usually 30-40 minutes that are timed to start every two hours during the day.

It is important prior to having an MSLT or MWT study that a 1-2 week sleep diary be completed and your Boarded Sleep Specialist Physician be aware of any medications (OTC or otherwise) that you are taking, since many medication can effect the results of this test.

The purpose of the MSLT has two purposes: first, to average the number of minutes that it takes to fall asleep (sleep onset latency) during all the naps and second, to record if REM stage sleep occurs during any of these scheduled napping periods.

The purpose of the MWT is to measure the amount of time it took the patient to fall asleep after being instructed to try to stay wake during the nap periods.

The testing procedure includes essentially the same PSG leads as for a diagnostic overnight study. During the periods between naps, the patient must stay awake and not fall asleep.

This test is particularly useful in helping people with Narcolepsy adjust their medication, diagnose Narcolepsy, objectively quantify the degree of sleepiness in a particular patient, such as an OSA (obstructive sleep apnea) patient who is still sleepy despite CPAP treatment and in diagnosing Idiopathic Hypersomnolence.
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