A type of sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine.

Polysomnography is a comprehensive recording of the biophysiological changes that occur during sleep.

Polysomnography is recommended in patients with a known or suspected history of stroke, a neuromuscular or pulmonary disorder with hypoventilation, or congestive heart failure or who are using opiates.

Usually performed at night.

Although some labs can accommodate shift workers and people with circadian rhythm sleep disorders and do the test at other times of day.

It monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG) and heart rhythm (ECG) during sleep.

Respiratory airflow and respiratory effort indicators have been added along with peripheral pulse oximetry.

Used to diagnose many types of sleep disorders including narcolepsy, idiopathic hypersomnia, periodic limb movement disorder, REM behavior disorder, parasomnias, and sleep apnea.

Indications for the test include sleep apnea, obesity, a risky neck diameter, or risky fullness in the oropharynx.

It typically records a minimum of 12 channels requiring a minimum of 22 wire attachments to the patient.

There is a minimum of three channels for the EEG, one or two measure airflow, one or two are for chin muscle tone, one or more for leg movements, two for eye movements (EOG), one or two for heart rate and rhythm, one for oxygen saturation and one each for the belts which measure chest wall movement and upper abdominal wall movement.

The electroencephalogram (EEG) provides a readout of the brain activity that can be divided into different stages of sleep (N1, N2, N3 which combined are ref2242ed to as NREM sleep, and Stage R which is rapid eye movement sleep or REM, and Wakefulness).

The electrooculogram (EOG) uses two electrodes; one that is placed 1 cm above the outer canthus of the right eye and one that is placed 1 cm below the outer canthus of the left eye.

These electrodes pick up the activity of the eyes in virtue of the electropotential difference between the cornea and the retina, and helps to determine when REM sleep occurs, of which rapid eye movements are characteristic, and also essentially aids in determining when sleep occurs.

The electromyogram (EMG) typically uses four electrodes to measure muscle tension in the body as well as to monitor for an excessive amount of leg movements during sleep.

Sleep generally includes relaxation and so a marked decrease in muscle tension occurs, but a further decrease in skeletal muscle tension occurs in REM sleep.

A person becomes partially paralyzed to make acting out of dreams impossible.

EKG electrodes and can be analyzed for any abnormalities that might be indicative of an underlying heart pathology.

Nasal and oral airflow can be measured using pressure transducers, and/or a thermocouple, to measure the rate of respiration and identify int2242uptions in breathing.

Pulse oximetry determines changes in blood oxygen levels that often occur with sleep apnea and other respiratory problems.

Snoring may be recorded with a sound probe over the neck.

Onset of sleep from time the lights are turned off, called sleep onset latency and normally is less than 20 minutes.

The determination of sleep and wake is based on the EEG, as sometimes feel they were awake when the EEG shows they were sleeping.

Sleep efficiency refers to the number of minutes of sleep divided by the number of minutes in bed.

Normal sleep efficiency is approximately 85 to 90% or higher.

4 sleep stages: 1, 2, 3, and REM or Rapid Eye Movement sleep. Stages 1–3 are together called non-REM sleep.

Within non-REM sleep, stage 3 is called slow wave sleep because of the relatively wide brain waves compared to other stages.

Another name for stage 3 is deep sleep.

Stage 1 and 2 are light sleep.

The percentage of each sleep stage varies by age.

There is decreasing amounts of REM and deep sleep in older people.

The majority of sleep at all ages, except infancy, is Stage 2.

REM normally occupies about 20-25% of sleep time.

Many factors besides age the amount and percentage of each sleep stage include: age, drugs , particularly anti-depressants and pain medication, alcohol and sleep deprivation, and breathing irregularities.

Arousals are sudden shifts in brain wave activity caused by numerous factors, including breathing abnormalities, leg movements, and environmental noises, cardiac rhythm abnormalities. leg movements, body position during sleep and oxygen saturation during sleep.

An abnormal number of arousals indicates an interrupted sleep and may explain daytime symptoms of fatigue and/or sleepiness.

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