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SLEEP MEDICINE


PROTOCOLS FOR ASSESSING SLEEPINESS AND ALERTNESS


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here are many consequences of sleep disorders. Some of these include impairment of daytime function. This impairment of


daytime function can be objectively evaluated in the sleep disorders center. Two methods used to assess the impact of sleep disorders are the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT). The MSLT measures a patient’s propensity towards sleep or hypersomnolence. The MSLT is also the definitive test for diagnosing narcolepsy. The MWT measures manifest sleepi- ness or the capacity to not be overwhelmed by sleepiness. The MSLT has been in use for many years and has a well-es-


tablished protocol for use in the clinical setting. This procedure is most commonly used to evaluate patients suspected of having nar- colepsy. It can also be employed when evaluating the complaint of hypersomnolence prior to the initiation of therapy for a sleep dis- order. Another use is evaluating the effectiveness of therapeutic in- terventions in place for previously diagnosed sleep disorders. Prior to performing the test, it is important to collect data re-


lating to the patient’s sleep patterns. This is usually done with self- reported sleep diaries for approximately two weeks. In some cases, actigraphy (motion sensor analysis of sleep) may be employed. The patient should undergo overnight PSG prior to the MSLT, and both studies, PSG and MSLT, should be performed in a manner that re- flects the patient’s routine sleep/wake schedule. Generally, patients are instructed to discontinue medications that would impact the testing for an appropriate washout period prior to the test. A drug screen is recommended to rule out the impact of medications (both prescribed and illicit) on the testing. The MSLT consists of a series of nap studies performed through-


out the day. The technologist performing the study should be well trained and well rested. One practice found in sleep centers is to have the overnight recording technologist perform the MSLT the following day. This puts the technologist at risk for sleep deprived errors that may negatively impact the validity of the test. It is hard to imagine someone staying awake all night to monitor a patient only to remain alert the following day while watching the patient sleep during multiple episodes of testing. The technologist will be evaluating the polysomnographic data to determine duration of the testing as well as the number of naps to be monitored. Errors in identifying sleep stages can create situations where the data from the MSLT is questionable in terms of diagnostic significance due to early termination of a nap that should have been fully performed. Patients who have been diagnosed with sleep apnea or any other sleep disorder may require the use of nasal CPAP. Prior to


20 Focus Journal Spring 2011


by Robert Turner RPSGT


the MSLT, patients should use CPAP for an adequate period of time to become accustomed to the device, as well as have ex- perienced the benefits of treatment. Diagnosis of coexisting nar- colepsy cannot be made until adequate treatment of sleep apnea, or other sleep problems such as periodic limb movement disorder, is complete. CPAP should be at the prescribed pressure during the nap. Patients are instructed to wear street clothes during the


MSLT portion of testing rather than remain in bedclothes worn during the PSG portion of testing. The first nap study may begin anywhere from 90 to 180


minutes following the final awakening from the PSG performed prior to the MSLT. All subsequent naps should begin 120 minutes from the beginning of any previous nap. For example, the patient awakens at 6:00 a.m. from PSG. The first nap may start anywhere from 7:30 a.m. to 9:00 a.m. If the first nap begins at 8:30 a.m., then the series of naps continues on a two hour schedule at 10:30 a.m., 12:30 p.m., 2:30 p.m. and 4:30 p.m. The standard number of naps to be performed is five. The diagnosis of nar- colepsy requires the observation of stage REM sleep in at least two of the naps. The last nap may be deleted if there have al- ready been two naps with stage REM sleep observed, or if there are no naps observed with stage REM sleep. The former is al- lowed since the diagnostic criteria for narcolepsy has already been met and the later because the diagnostic criteria cannot be met even if the patient exhibits stage REM sleep during the final nap.


The protocol requires monitoring of central and occipital


EEG, right and left EOG, chin EMG and ECG. Additional upper and lower EOG leads are optional and can be helpful in identi- fying stage REM sleep. Any additional leads normally monitored during routine PSG may be utilized, but they are optional. Pa- tients are studied lying in bed with the room darkened as com- pletely as possible. External stimuli that would compete with sleeping such as noise and temperature should be controlled to allow for a comfortable sleeping environment. Prior to each nap, physiological or patient calibrations are performed to verify the proper function of each lead. Patients should be given a subjec- tive measure of sleepiness such as the Stanford Sleepiness Scale. The patient is then instructed to try to fall asleep, lights are turned out and the official timing of the test begins. Following lights out, the technologist must observe closely for the appearance of sleep to determine when the study is to


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