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Tachycardia
Rapid heart rate, usually defined by a pulse rate of over 100 beats per minute (bpm).
Thermocouples
Small devices placed near the nostrils or mouth to measure air flow by sensing temperature changes; expired air is warmer than inspired air.
Thermoregulation
Regulation of body temperature in mammals.
Theta waves
EEG activity with a frequency of 4-8 Hz
Thoracic Excursion
Thoracic (chest) movement, indicating respiratory effort. Usually measured by the placement of a sensor band, which includes a strain gauge around the chest. The sensor band records chest wall movement associated with respirations..
Tidal Volume
Amount of air that passes in and out of the lungs in an ordinary breath; usually expressed in liters
Titration
Progressive, stepwise increase in CPAP pressure applied during a polysomnogram to establish the optimal treatment pressure
Tolerance
In pharmacology, refers to the reduced responsiveness to a drug's action as the result of previous continued and/or multiple exposure
Tonic (Event/Activity)
Brain, muscle, or autonomic events, which are continuous. Usually refers to continuous activity (e.g. muscle atonia) during REM sleep.
Tonsillectomy
Surgical removal of the tonsils
Tonsils
Pair of prominent masses of lymphoid tissue that are located opposite each other in the throat between the anterior and posterior pillars of the fauces (the narrow passage from the mouth to the pharynx situated between the soft palate and the base of the tongue). Composed of lymph follicles grouped around one or more deep crypts.
Total Recording Time
Duration of time from sleep onset to final awakening. I n addition to total sleep time, it is comprised of the time taken up by wake periods and movement time until wake-up.
Total sleep period
Period of time measured from sleep onset to final awakening. In addition to total sleep time, it is comprised of the time taken up by arousals and movement time until wake-up
Total sleep time (TST)
Amount of actual sleep time in a sleep period; equal to total sleep period less movement and awake time. Total sleep time is the total of all REMS and NREMS in a sleep period.
Tracheostomy
Refers to the opening in the trachea. As a treatment for severe obstructive sleep apnea, a tube to assist oxygenation and ventilation and/or to overcome an obstruction in the airway located superiorly.
Tracheotomy
Surgical procedure to create an opening in the trachea (windpipe) so that one can breathe
Transducer
Device designed to convert energy from one form to another
Transient Arousals
Brief awakenings from sleep
Transient Insomnia
Difficulty sleeping for only a few nights
Tricyclic Antidepressants
Medication for depression. Most tricyclic antidepressants also reduce REM sleep; also used to control cataplectic attacks, hypnogogic hallucinations, and sleep paralysis.
Tumescence (penile)
Hardening and expansion of the penis: penile erection. Commonly referred to as nocturnal penile tumescence (NPT) in sleep recordings.
Turbinate
Small, shelf-like, cartilaginous structures covered by mucous membranes, which protrude into the nasal airway to help warm, humidify, and cleanse inhaled air on its way to the lungs.
Twilight Zone
Slang popular term to describe the waking state of individuals whose MSLT scores are 5 minutes or less. Such individuals are usually sleep deprived or suffer from a sleep disorder.
Twitch (Body Twitch)
Very small body movement such as a local foot or finger jerk which is not usually associated with an arousal.
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