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Sleep Apnea Definitions – I To Q

August 29th, 2009


Sleep Apnea Definitions – I To Q

These are a list of common definitions from I to Q as used in discussions about Sleep Apnea.

Imidazopyridines – New class of compounds inducing sleepiness. (Zolpidem, trade name Ambien, is in this class).

Inappropriate Sleep Episodes – unplanned sleep periods often occuring in an unsafe situation (i.e., while driving). These episodes are always due to sleep deprivation.

Insomnia – complaint describing difficulty in sleeping

Inspiratory Phase – part of the breathing cycle in which air is inhaled.

Invasive – referring to a medical procedure in which a bodily orifice or the skin must be penetrated for the purpose of collecting data, or for diagnosing or treating a disorder

IPAP – Inspiratory Positive Airway Pressure.  Physician prescribed pressure for the inspiratory phase on a Bi-level CPAP device, used in the treatment of OSA.

Jet Lag – disturbance induced by a major rapid shift in environmental time during travel to a new time zone

K-Alpha – type of microarousal;  K complex followed by several seconds of alpha rhythm.

K complex – sharp, negative, high-voltage EEG wave, followed by a slower, positive component. K complex, occurring spontaneously during NREM sleep, beginning in (and defining) stage 2.  K complexes can be elicited during sleep by external (particularly auditory) stimuli as well.

Laser assisted uvulopalatoplasty (LAUP) – can eliminate or decrease snoring but has not been shown to be effective in the treatment of sleep apnea.

Leg Movement – Leg movements are recorded in both diagnostic sleep studies and titration studies.

Letter of Medical Necessity (LMN) – certification by a physician that the prescribed item(s) is/are medically indicated, reasonable and necessary with reference to the standards of medical practice and treatment of a patient’s condition

Light-Dark Cycle – periodic pattern of light (artificial or natural) alternating with darkness

Light Sleep – term used to describe non-REM sleep stage 1, and sometimes, stage 2.

Light Therapy – used in the treatment of SAD (Seasonal Affective Disorder) and other conditions. Exposes the eyes to light of appropriate intensity and duration and at the appropriate time of day to effect the timing, duration and quality of sleep.

Limit-Setting Sleep Disorder – disorder due to child’s difficulty in falling asleep by delaying and refusing to go to bed

Linear Sleepiness Rating Scale – measure of subjective sleepiness.  The scale contains a horizontal line, 100 mm in length –the right extreme is labeled “Very Sleepy” and the left extreme is labeled “Very Wide Awake.”

Macroglossia – large tongue; usually a congenital disorder (present at birth)

Maxillofacial – pertaining to the jaws and face.

Mandibular Maxillary Osteotomy and Advancement (MMOA) – procedure developed for patients with retrolingual obstruction, patients with retropalatal and retrolingual obstruction who have not responded to CPAP and uvulopalatopharyngoplasty (UPPP).

Melatonin – hormone secreted by the brain’s pineal gland

Micro-arousal – partial awakening from sleep

Micro-sleep – period lasting up to a few seconds during which the polysomnogram suddenly shifts from waking characteristics to sleep.

Mixed (sleep) apnea – interruption in breathing during sleep beginning as a central apnea then becoming an obstructive apnea.

Monocyclic – a single major sleep period and a single major wake period in a 24-hour day.

Motor Activity in Sleep – any muscular movement during sleep

Motor Atonia – the absence of muscle activity during sleep

Movement arousal – body movement associated with arousal or awakening; a sleep scoring variable.

Movement time – term used in sleep record scoring to denote when EEG and EOG tracings are obscured for more than 15 seconds due to movement.

Multiple sleep latency test (MSLT) – a series “nap tests” utilized in the assessment of excessive daytime sleepiness.

Muscle Tone – amount of tension in a muscle.

Myoclonus – muscle contractions in the form of “jerks” or twitches.

Nap – short period of planned sleep generally obtained at a time separate from the major sleep period.

Narcolepsy – sleep disorder characterized by excessive sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, and an abnormal tendency to pass directly from wakefulness into REM sleep

Nasal Airflow/Nasal Ventilation – recording of the complete respiratory cycle by measuring inspiratory and expiratory airflow

National Commission on Sleep Disorders Research (NCSDR) – the commission (created by the U.S. Congress in 1990) conducted a comprehensive study of the social and economic impact of sleep disorders in America and made recommendations based on its findings to the Congress in January 1993

Neurology – branch of medicine that referring to the nervous system and its diseases

Neurotransmitters – endogenuous chemical components that are released from axon terminals of one neuron and transmit the signal to the next neuron by combining with its receptor molecules.  Neurotransmitters important in the control of sleep and wakefulness include: norepinephrine, serotonin, acetylcholine, dopamine, adrenaline and histamine.

Nightmare – unpleasant and/or frightening dream occurring in REM sleep (different from a night terror)

Night Terrors – also known as sleep terrors, or pavor nocturnus.  Night terrors are characterized by an incomplete arousal from slow wave sleep.  If, the individual is awakened during a night terror, he/she is usually confused and does not remember details of the event. Night terrors are different from nightmares; if an individual is awakened during a nightmare, he/she functions well and may have some recall of the nightmare.

Nocturia – excessive, often frequent, urination during the night

Nocturnal – “Of the night;” pertaining to events happening during sleep or the hours of darkness.

Nocturnal Confusion – episodes of delirium and/or disorientation near or during nighttime sleep; often seen in victims of Alzheimers Disease and more common in the elderly

Nocturnal sleep-related eating disorder (NS-RED)– Getting up during the night and eating while sleepwalking. No recall in the morning.

Nocturnal Enuresis (Bedwetting) – urinating while asleep

Non-Invasive – Medical procedure not penetrating the skin or a body cavity.

NREM or non-REM sleep – characterized by slower and larger brain waves and little or no dream behavior;  quiet sleep, slow-wave sleep;  approximately 80% of sleep

NREM Sleep Intrusion – brief period of NREM sleep patterns appearing in REM sleep;  a portion of NREM sleep not appearing in its usual sleep cycle position


Obesity-Hypoventilation Syndrome – term applied to obese individuals hypoventilating during wakefulness.

Obstructive apnea – cessation of airflow (at least 10 seconds) in the presence of continued inspiratory effort;  cessation of breathing during sleep, due to a mechanical obstruction, such as a semi-collapsed trachea, tongue relaxed to back of the throat, or a large among of tissue in the uvula area.

Obstructive Hypopnea – periodic and partial closure of the throat during sleep resulting in reduced air exchange at the level of the mouth and/or nostril.

Ondine’s Curse – the respiratory center in the brain is unable to stimulate breathing in response to an increased amount of carbon dioxide in the blood.  Ondine’s Curse or central alveolar hypoventilation typically worsens during sleep.

Optimum Sleep – average amount of sleep needed every night by an individual.

Oxygen Desaturation – less than normal amount of oxygen carried by hemoglobin in the blood;  values below 90% are considered abnormal

Oxygen Saturation – measure of oxygen carried by hemoglobin in the blood. Normal values 90% – 100%.

Oximeter (Pulse) – gives estimates of arterial oxyhemoglobin saturation (SaO2) by utilizing selected wavelengths of light to non invasively determine the saturation of oxyhemoglobin (SpO2)

Oximetry (Pulse) – continuous monitoring of oxygen saturation of arterial blood from a pulse oximeter;  the sensor is usually attached to the finger.

O2 – Chemical symbol for oxygen. Criterion lowest percent O2 saturation: Greater than 85%=mild, 80% to 85%=moderate, less than 80%=severe

Parasomnia – an event happening during sleep, or induced or exacerbated by sleep, such as sleepwalking or asthma; not a dyssomnia.

Paroxysmal nocturnal dyspnea (PND) – respiratory distress and shortness of breath due to pulmonary edema, appearing suddenly and often awakening the sleeping individual.

Pathological Sleep – abnormal sleep patterns. Pavor

Nocturnus (Night Terrors) – See Night Terrors.

Perceptual Disengagement – change in consciousness at the onset of sleep when environmental stimuli are no longer perceived, and there is no longer any conscious, meaningful interaction with the environment.

Periodic Breathing – repetitive apneic pauses, common in premature infants.

Periodic Limb Movement Disorder – also known as periodic leg movements and nocturnal myoclonus. Characterized by periodic episodes of repetitive and highly stereotyped limb movements occuring during sleep. The movements are often associated with a partial arousal or awakening; however, the patient is usually unaware of the limb movements or frequent sleep disruption.  Between the episodes, the legs are still. There can be marked night-to-night variability in the number of movements or in the existence of movements.

Persistent Insomnia – continuing insomnia responding poorly to treatment.

Pharynx – area posterior to the nares and the oral cavity;  passageway for air from the nasal cavity and/or the mouth to the lungs via the larynx and the trachea, for food and liquids from the mouth to the esophagus Phase advance – movement to a position earlier in the 24 hour sleep – wake cycle of a period of sleep or wake; for example, a shift of the sleep phase from 11 p.m. – 7 a.m. to 8 p.m. – 4 a.m.

Phase delay – Phase delay is exactly the opposite of phase advance, i.e., a shift later in time.

Phasic (Event/Activity) – brain, muscle, or autonomic related event of a brief and episodic nature occurring in sleep. Usually  occur during REM sleep, such as eye movements and/or muscle twitches

Photoperiod – duration of light in a light/dark cycle.

Pickwickian Syndrome – obesity accompanied by somnolence, lethargy, chronic hypoventilation, hypoxia, and secondary polycythemia (a condition marked by an abnormal increase in the number of circulating red blood cells);  usually has severe obstructive sleep apnea

Pineal Gland – gland in the brain secreting the hormone melatonin.

PLMD-Arousal Index – number of sleep-related periodic leg movements per hour of sleep that are associated with an EEG arousal

Polycyclic – multiple sleep periods and wake periods in a 24-hour day. PO2 – partial pressure of oxygen (O2) in the blood. A value above 60 is usually considered a safe level:  lower than 60 indicated hypoxemia and potential danger for the patient.

Polysomnogram (PSG) – continuous and simultaneous recording of physiological variables during sleep, i.e., EEG, EOG, EMG (the three basic stage scoring parameters), EKG, respiratory air flow, respiratory excursion, lower limb movement, and other electrophysiological variables.

Polysomnograph – biomedical instrument for the measurement of multiple physiological variables of sleep

Polysomnographic Technologist – health care professional trained in performing diagnostic sleep studies

Post-Prandial Drowsiness – sleepiness that occurs after a meal, usually lunch

Post-Traumatic Stress Disorder – re-experiencing of a traumatic event in the form of repetitive dreams, recurrent and intrusive daytime recollections, and/or dissociative flashback episodes.

Premature morning awakening – early termination of the sleep period in a sleep maintenance DIMS due to inability to return to sleep after the last of several awakenings

Prescribed CPAP Pressure – pressure(s) or settings determined by a CPAP titration sleep study, which a physician prescribes for a patient’s CPAP therapy machine

Pulse Oximetry – non-invasive measure of oxygen saturation; that is the amount of oxygen saturated in the hemoglobin in terms of percentage;  not as accurate as the values obtained from an arterial blood gases (ABG) test and should only be used as a gauge of oxygenation. Normal ranges are between 95-100%.

Quiet Sleep – The term frequently used instead of NREM sleep to describe the sleep of infants.

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