Article - Diagnosing Sleep DIsorder using a polysomnogram

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A consists of a simultaneous recording of multiple physiologic parameters

related to sleep and wakefulness. The interaction of various organ systems

during sleep and wakefulness also is evaluated.

Polysomnography (PSG) is used to evaluate abnormalities of sleep and/or

wakefulness and other physiologic disorders that have an impact on or are

related to sleep and/or wakefulness.

By international standards, a polysomnogram must have a minimum of 4

neurophysiologic channels.

a.. One electroencephalography (EEG) channel (central with an ear reference

provides the best amplitude) to monitor sleep stage

a.. Two electrooculogram (EOG) channels to monitor both horizontal and vertical

eye movements (electrodes are placed at the right and left outer canthi, 1 above

and 1 below the horizontal eye axis)

a.. One electromyography (EMG) channel (usually chin or mentalis and/or

submentalis) to record atonia of rapid eye movement (REM) sleep

Other parameters often monitored include the following:

a.. Additional EEG channels, particularly in patients with sleep-related

epilepsy

a.. Additional EMG channels, particularly anterior tibialis, to detect periodic

limb movements of sleep

a.. Airflow

a.. Electrocardiogram

a.. Pulse oximetry

a.. Respiratory effort

a.. Sound recordings to measure snoring

Optional parameters include the following:

a.. Continuous video monitoring of body positions

a.. Core body temperature

a.. Incident light intensity

a.. Penile tumescence

a.. Pressure and pH at various esophageal levels

In 1992, the Office of Technology Assessment of the Agency of Health Care Policy

and Research recommended, in an evidence-based assessment, 2 tests as having

been studied sufficiently. Both tests are performed in a sleep laboratory.

a.. Overnight polysomnography (oPSG) is an overnight recording of the patient's

sleep.

a.. Multiple sleep latency testing (MSLT) records multiple naps throughout a

day.

Standard sleep studies usually include both tests, oPSG (may be performed over

several nights) followed by MSLT the next day. Limitations usually stem from the

fact that recording conditions may not reflect what happens during a regular

night in the patient's home.

Although diagnosing a sleep problem on the basis of a recording over a single

night is common practice, some authorities caution that more than 1 night of

recording may be necessary, so the patient may become comfortable with

unfamiliar surroundings and sleep more naturally. This effect is greatest on the

first night in the sleep laboratory ( " first night effect " ).

Sporadic events may be missed on a 1-night PSG. External factors that disturb

the subject's sleep may be present in the home but absent from the controlled

environment of the sleep lab.

Patient preparation is important so that the patient sleeps naturally. Patient

instructions include the following:

a.. Maintain regular sleep-wake rhythm

a.. Avoid sleeping pills

a.. Avoid alcohol

a.. Avoid stimulants, including medications for narcolepsy

a.. Avoid strenuous exercise on the day of PSG testing

High costs and long waiting lists have prompted the exploration of alternative

methods of evaluation. Although the following studies may have usefulness in

specific clinical situations, Bloch concludes that their role compared to

conventional sleep studies remains controversial.

a.. Ambulatory monitoring with portable equipment

a.. Daytime PSG

a.. Simplified sleep studies with limited subsets of monitored parameters

Automatic, computer-based systems often are employed in clinical and research

settings. However, standard analysis still consists of tedious and

time-consuming review and scoring of either paper tracings or recordings

projected on a computer monitor.

Overnight parameters (eg, times of lights on/off, total time in bed, total sleep

time) are collected. The overnight recording is divided into epochs of

approximately 30 seconds. The standard EEG, EMG, and EOG recordings are

evaluated, and the predominant stage of sleep (according to the manual of

Rechtschaffen and Kales) then is assigned to the entire epoch.

Total time and relative proportion of the night spent in each of the 6 stages

and in REM and non-REM sleep are calculated. Latencies to REM and slow-wave

sleep (SWS) are reported.

Special neurophysiologic events (eg, epileptic events, intrusion of alpha into

sleep, periodic activity of tibialis anterior) are reported. Respiratory

activity (eg, apneic or hypopneic episodes, oxygen saturation) is correlated

with sleep stages. Other parameters such as body position, gastroesophageal

reflux, bruxism, and penile tumescence are recorded.

If a sleep apnea syndrome is diagnosed, a trial and titration of continuous

positive airway pressure or a trial of an oral appliance may be undertaken,

either in a partial-night or second-night PSG recording.

Dyssomnias (disorders of initiating or maintaining sleep)

a.. Circadian rhythm disorders

a.. Narcolepsy

a.. Idiopathic hypersomnia

a.. Inadequate sleep hygiene

a.. Sleep-related respiratory disorders

a.. Sleep apnea syndrome

b.. Upper airway resistance syndrome

Parasomnias

a.. Disorders of arousal

a.. Disorders of sleep-wake transition

a.. Disorders that occur during REM sleep

a.. Nightmares

b.. REM behavior disorder

a.. Medical-psychiatric sleep disorders

a.. Medical - Sleep-related asthma

b.. Psychiatric

a.. Depression

b.. Panic disorder

c.. Neurologic - Sleep-related epilepsy

a.. Others

a.. Bruxism

b.. Restless legs syndrome and periodic limb movement disorder