Sleep Disorders Glossary U, V, W AND Z

Sleep Disorders Glossary - U, V, W AND Z

Ultradian Rhythm

Ultradian rhythm is a periodicity of less than 24 hours.

Unattended CPAP Titration Study

Unattended CPAP Titration Study is sleep study that is usually performed in the home, after determining that a patient has a sleep related breathing disorder such as OSA or Upper Airway Resistance Syndrome, and is likely to benefit from CPAP therapy .

Unihemispheric Sleep

unihemispheric sleep a type of sleep in which one side of the brain is asleep while the other is awake. This phenomenon is observed most notably in birds and aquatic mammals.

Unintended Sleep Episode

Unintended Sleep Episode is a sleep period that is not planned and may happen during an activity in which such an episode is dangerous, such as when driving a car or working with machinery.

Upper Airway

Upper airway is portion of the respiratory tract that extends from the nostrils or mouth through the larynx .

Upper Airway Resistance Syndrome / UARS

Upper Airway Resistance Syndrome is a condition in which patients complain about excessive daytime sleepiness and there are symptoms of airway resistance. However, patients do not meet the criteria for sleep apnea and they do not show reduction in oxygen levels in the blood. Unlike apnea, it is more likely to occur in women than in men.


Urotoxins is a term he used to describe toxic agents excreted in the urine during sleep. It was coined by Abel Bouchard in 1886


Uvula is the small, conical, fleshy mass of tissue suspended from the center of the soft palate.

Uvulopalatopharyngoplasty [UPPP]

Uvulopalatopharyngoplasty (UPPP) is a procedure used to decrease or remove the sound of snoring in human beings during sleep. The procedure involves removing excess tissue in the throat, widening the airway. More air is then able to pass through the airway, and snoring is usually decreased.

The procedure is used to "cure" snoring for the benefit of other people who are affected by the loud snoring of the patient. Loud snoring can cause a loss of sleep in those that hear it. This procedure is also used to treat obstructive sleep apnea.

Vigilance Testing

Vigilance testing is the procedure of evaluating the level of alertness during wakefulness in a clinical or research setting. It may include a series of tests such as the Epworth Sleepiness scale, pupillometry, reaction time tests, a MLST, or MWT.


Wakefulness is a state of brain that occurs when a healthy individual is not asleep.

Wake Time

Wake Time is the total time scored as wakefulness in a polysomnogram occurring between sleep onset and final awakening.

White Noise

White noise is the heterogeneous mixture of sound waves expanding over a wide frequency range that may be used to mask unnecessary noise that may obstruct with sleep

Wilkinson Addition Test

Wilkinson Addition Test is a performance test in which the subjects add numbers for one hour. Often included in a battery of tests to measure the impact of acute or chronic sleep loss.


Withdrawal is the negative effects experienced when a patient stops taking sleeping pills .


Zeitgeber are environmental cues that usually help keep circadian rhythms entrained. They reset the internal clocks that generate endogenous rhythms. Zeitgebers include sunlight, noise, social interactions, and alarm clocks.


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