Sleep Disorders Glossary O

Sleep Disorders Glossary - O

Obesity-Hypoventilation Syndrome/Pickwickian Syndrome

Obesity-Hypoventilation Syndrome is a distinctive form of obstructive sleep apnea associated with being overweight, having a large neck, fat buildup around the soft tissues of the neck, and loss of muscle tone with aging

It is the combination of severe obesity, suffering from obstructive sleep apnea causing hypoxia and hypercapnia resulting in marked daytime somnolence . It is also known as Pickwickian Syndrome.

Obstructive Hypopnea

Obstructive Hypopnea is the episodic, partial closure of the throat during sleep, which results in reduced air exchange. The medical consequences of this partial closure can be as severe as sleep apnea.

Obstructive Sleep Apnea /OSA/ Obstructive Apnea

Obstructive sleep apnea (syndrome) is the most common form of sleep apnea characterized by repeated episodes of upper airway obstruction during sleep. It is also called as OSA.

Ondine's Curse

Ondine's Curse is a respiratory disorder that is fatal if untreated. Persons afflicted with Ondine's curse are unable to breathe without conscious intervention . It is also called as central alveolar hypoventilation syndrome, or primary alveolar hypoventilation.


Opiate any of a group of drugs derived from opium. Used medicinally to relieve pain and induce sleep, they include codeine, morphine, the morphine derivative heroin, and, formerly, laudanum.

Sometimes included in the group are certain synthetic drugs that have morphinelike pharmacological action. It is used to manage severe cases of Restless Legs Syndrome and Periodic Limb Movement Disorder.

Optimum Sleep

Optimum Sleep is the average amount of sleep needed for an individual. Most adults require about 7 to 8.5 hours per night, although this number is subjective, and may vary from person to person.


Oscillograph is a device that displays ongoing physiological patterns (EEG) or other variables usually tracing on moving paper or a CRT screen.


Orexin is another name for hypocretin, a chemical secreted in the hypothalmus that regulates the sleep/wake cycle. Narcolepsy is sometimes described as an orexin deficiency syndrome.


Otolaryngology is the branch of medicine that deals with diagnosis and treatment of diseases of the ear, nose, and throat.

Over-the-counter medications/ OTCs

Over-the-counter medications are the drugs that are available to the general public without any prescription. They are also called as OTCs.


Oximeter is a device for measuring the oxygen saturation of arterial blood .


Oximetry is a procedure for measuring the concentration of oxygen in the blood .

Oxygen Desaturation

Oxygen Desaturation is referred to as hemoglobin in the blood carries less than normal amount of oxygen. A value below 90% is considered abnormal.

Oxygen Saturation

Oxygen Saturation (SaO 2) measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. At low partial pressures of oxygen, most hemoglobin is deoxygenated.

At around 90%, oxygen saturation increases according to an S curve and approaches 100% at partial oxygen pressures of >10 kPa. A pulse oximeter relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation.

A SaO 2 value below 90% is termed hypoxemia. This may be due to various medical conditions.


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