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Acidosis
A pathologic condition resulting in the accumulation of acid or loss of base in the body; Respiratory acidosis is the state of excess retention of carbon dioxide

Actigraph
An instrument for the measurement of body movement

Adult Respiratory Distress Syndrome (ARDS)
Indicates respiratory failure with life threatening distress and hypoxemia, associated with acute pulmonary injuries

Aerophagia
The swallowing of air

Aerosol
Tiny solid or liquid particles floating in air like a gas

Airway Resistance (RAW)
A measure of the impedance to ventilation caused by the movement of gas through the airways; Abbreviated as RAW, airway resistance is computed as a change in pressure along a tube divided by flow

Alkalosis
A condition in which the alkaline content in the blood increases above normal limits

Allergen
Any substance that causes an allergy; A substance capable of producing an immediate hypersensitive (allergic) reaction

Allergy
An acquired, abnormal immune response to a substance (allergen) that does not normally cause a reaction; Contact with the allergen results in a broad range of inflammatory responses

Alpha Activity
Rhythm at 8-13 Hz, characteristic of relaxed wakefulness with eyes closed

Alpha-delta Sleep
Sleep in which alpha activity occurs during slow-wave sleep

Alveolar Hypoventilation
The inability to exchange sufficient amounts of air between the room and the lung to allow for gas exchange that produces normal gas concentrations of oxygen and carbon dioxide in the blood

Alveoli
Microscopic air sacs located at the end of the respiratory tract; Grape-like clusters of sacs that allow inhaled oxygen to enter the bloodstream and carbon dioxide to leave the bloodstream

Apnea
An absence of breathing (respirations); See also Pathological Apnea, Central Apnea, Obstructive Apnea, Mixed Apnea

Apnea Index
The number of apneic episodes (obstructive, central, and mixed) per hour of sleep

Apnea of Infancy (AOI)
An unexplained episode of cessation of breathing for 20 seconds or longer, or a shorter respiratory pause associated with bradycardia, cyanosis, pallor, and/or hypotonia; AOI refers to infants who are greater than 37 weeks gestational age at onset of pathological apnea

Apnea of Prematurity (AOP)
Periodic breathing with pathologic apnea in a premature infant; AOP usually ceases by 37 weeks gestation, but occasionally persists to several weeks past term

Apnea-hypopnea Index (A/HI)
The number of apneic episodes (obstructive, central, and mixed) plus hypopneas per hour of sleep; Synonymous with respiratory disturbance index

Apparent Life Threatening Event (ALTE)
An episode that is frightening to the observer and that is characterized by some combination of apnea, color change, marked change in muscle tone, choking or gagging

Arousal
An abrupt change from a deeper sleep stage to a lighter sleep stage, with the possibility of awakening as a final outcome; Arousal may be accompanied by increased muscle tone and heart rate as well as body movement

Arrhythmia
Abnormal rhythm of the heart, which could be an abnormality of rate, regularity, presence of extra beats or missing beats

Arterial Blood Gas (ABG)
A term used to describe the assessment of arterial blood gas levels of oxygen (Pa02) and carbon dioxide (PaC02)

Aspiration
Inhalation of any foreign matter, such as food, saliva or stomach contents into the airway

Assist/Control (A/C, CMV, AC)
Continuous mandatory ventilation (CMV) in which the minimum breathing rate is predetermined by the ventilator controls, but the patient can initiate ventilation at a faster rate

Asthma
A chronic disease characterized by attacks of breathlessness, accompanied by wheezing, coughing and chest tightness; An obstructive inflammatory disease that affects the airways, sometimes making it difficult to breathe

Asthma Action Plan
A treatment plan and instructions prescribed by a healthcare provider, which will teach patients to take medications and adjust them accordingly as asthma conditions change in order to keep asthma under control

Atelectasis
A shrunken and airless state of part or the entire lung; the disorder may be chronic or acute; May be caused by secretions, obstruction by foreign bodies or compression

Auto-PEEP
Abnormal and usually undetected residual pressure above atmospheric remaining in the alveoli at end-exhalation due to dynamic air-trapping

Awakening
The return to the awake state from any non-REM or REM sleep stage.

Bacterial Pneumonia
An inflammation and infection caused by bacteria

Barotrauma
Injury resulting from high levels of pressure differential in the lungs

Baseline
The typical or normal state of an individual or of a parameter before change

Beta Activity
EEG rhythm in the range of 13-35 Hz, is usually associated with alert wakefulness or vigilance

Bi-Level or BiPAPTM(BiPAP)
Bi-level Positive Airway Pressure; Used to treat sleep apnea, and other sleep related breathing disorders; Delivers alternating levels of inspiratory pressure (IPAP), or higher pressure, to keep the airway open as a patient breathes in, and the expiratory pressure (EPAP) is lower to reduce the work of exhaling; the BiPAP can be set to drop the level at specific intervals, or upon demand

Bilirubin
A yellow compound produced by the breakdown of hemoglobin from red blood cells

Bradycardia
Slowing of the heart rate below the age specified rate for 5 seconds or greater

Bronchodilator
Any number of drugs that enlarge the bronchial air passage either by shrinking the mucus membranes or by relaxing the smooth muscles that constrict the air passages

Bronchospasm
An abnormal contraction of the smooth muscle of the bronchi, resulting in acute narrowing and obstruction

Bruxism
The habit of unconsciously gritting or grinding the teeth especially in situations of stress or during sleep

Cataplexy
A sudden decrement in muscle tone and loss of deep tendon reflexes leading to muscle weakness, paralysis, or postural collapse; One of the symptom tetrad of narcolepsy

Central Apnea
No respiratory effort, caused when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations

Cheyne-Stokes Respiration
A pattern of breathing with a gradual increase in the depth of respiration to a maximum, followed by a progressive decrease in the depth of respiration resulting in apnea, characteristically seen in heart failure patients

Chronic
Lasting a long time or recurring; Having an ailment for a long time

Chronic Obstructive Pulmonary Disease (COPD)
A progressive disease process that most commonly results from smoking; COPD is characterized by difficulty breathing, wheezing and a chronic cough

Circadian Rhythm
An innate, daily fluctuation of physiologic or behavioral functions, including sleep-wake states generally tied to the 24-hour clock

Colonization
The process in which microorganisms establish a presence and grow in or on the human body; Does not necessarily indicate a pathological response

Compliance (CHF)
Compliance is the consistency and accuracy with which a patient follows the regimen prescribed by a physician or other health professional; The relative ease with which a body stretches or deforms; In pulmonary physiology, a measure of volume change per unit pressure under static conditions; The reciprocal of elastance (i.e., L/cmH20)

Continuous Mandatory Ventilation (CMV)
An abbreviation for continuous mandatory ventilation; The application of pressure greater than atmospheric at the airway opening during every inspiration, used to support ventilation

Continuous Positive Airway Pressure (CPAP)

Medical device that delivers a steady, gentle flow of air delivered through a soft, pliable nasal mask Medical device that delivers a steady, gentle flow of air delivered through a soft, pliable nasal mask worn over the nose; Used to 'splint' open a person's airway during sleep; CPAP is the most effective treatment available for Obstructive Sleep Apnea

Cyanosis
Bluish coloration of the skin caused by deficient oxygenation of the blood

Cycle
The complete series of potential changes undergone by a wave before the same series is repeated; Such as the REM cycle

Deadspace
Respired gas volume that does not participate in gas exchange; May be anatomic, alveolar or mechanical

Deep Sleep Stage
Common term for NREM stages 3 and 4 sleep; In deep sleep, a person is very difficult to arouse; Mostly occurs at the beginning of the night

Delayed Sleep Phase
A condition that occurs when the clock hour at which sleep normally occurs is moved ahead in time within a 24-hour sleep-wake cycle; Commonly known as Delayed Sleep Phase Syndrome

Delta Activity
EEG activity of 75 uV amplitude (peak-to-peak) and 0.5 seconds’ duration (2Hz) or less

Delta Sleep Stage
The stage of sleep in which EEG delta waves are prevalent or predominant- Sleep stages III and IV

Diagnostic Criteria
Specific criteria established in the International Classification of Sleep Disorders to aid in determining the unequivocal presence of a particular sleep disorder

Disorganized Breathing
A breathing pattern consisting of irregular breathing with short periods of apnea, usually accompanied by heart rate decelerations and/or bradycardia; Can be a signal that the patient being monitored is awake

Drowsiness
A stage of quiet wakefulness that typically occurs before sleep onset; If the eyes are closed, diffuse slowed alpha activity usually is present, which then gives way to early features of Sleep stage I

Dynamic Compliance
A measure of distensibility of the lungs during breathing (i.e., the pressure required to obtain a given volume of inflation)

Dyspnea
Shortness of breath

Dysynchrony
Pertaining to ventilatory support, a situation in which interaction between the patient and machine is poorly coordinated, causing extra patient effort and discomfort

Ear, Nose and Throat (ENT)
Used to refer to a physician that specializes in disorders of that region; Technically known as an Otorhinolaryngologist

Edema
A local or generalized condition due to the build-up of excessive amounts of extra-cellular fluid and characterized by swelling

Electro-encephalogram (EEG)
A recording of the electrical activity of the brain by means of electrodes placed on the surface of the head

Electro-oculogram (EOG)
A recording of the electrical activity of the eyes; Used to verify sleep changes including REM

Electromyogram (EMG)
A recording of electrical activity from the muscular system/muscle activity; Used to assist in the scoring of sleep stages such as REM; Also used to measure muscle activity to help diagnose PLMS

Epoch
A measure of duration of the sleep recording typically 20-30 seconds; An epoch corresponds to one page of the polysomnogram

Exacerbation
A worsening of a condition, usually acutely

Excessive Daytime Sleepiness or Somnolence (EDS)
A subjective report of difficulty in maintaining the awake state, accompanied by a ready entrance into sleep when the individual is sedentary; May be quantitatively measured by use of subjectively defined rating scales of sleepiness

Expiratory Phase (Exhalation)
The part of the ventilatory cycle from the beginning of expiratory flow to the beginning of inspiratory flow

Expiratory Positive Airway Pressure (EPAP)
The lower pressure used in BiPAP; Helps maintain airway patency and oxygenation

Extubation
The removal of a tube that has been inserted into the airway

FI02
The fraction of inhaled oxygen expressed as a percent; Room air has an FI02 of 21%

Final Awakening
The duration of wakefulness after the final wake-up time until the arise time (lights on)

First-night Effect
The effect of the environment and polysomnographic recording apparatus on the quality of the subject's sleep during the first night of recording

Flare-up
Commonly known as an asthma attack; When asthma condition is out of control

Flow Trigger
Initiation of inspiration when the patient's inspiratory effort exceeds the flow sensitivity setting (threshold)

Fragmentation (of sleep architecture)
Connotes repetitive interruptions of sleep by arousals and awakening

Free-running
A chronobiological term that refers to a person that has an impaired ability to entrain sleep or is without time cues

Functional Residual Capacity(FRC)
The total amount of gas left in the lungs after a resting expiration

Gastroesophageal Reflux (GER)
The regurgitation of stomach contents back into the esophagus

Heart Rate
The number of heart beats per minute

Heel Stick
A procedure in which a newborn's heel is pricked so that a small amount of blood can be collected in order to be used to do newborn screening tests

Humidity
Water in molecular vapor form; Absolute humidity is a measure of the actual content or weight of water present in a given volume of air; Relative humidity is the ratio of actual water vapor present in a gas to the capacity of the gas to hold the vapor at a given temperature

Hyperbilirubinemia
A high level of bilirubin in the blood

Hypercapnea
An elevated level of carbon dioxide in the blood; PaC02 typically over 45 mmHg

Hypersomnia
Excessively deep or prolonged sleep period; Symptom is described as excess sleepiness

Hypnogogic Startle
A "sleep start" or sudden body jerk (hypnic jerk, observed normally just at sleep onset)

Hypopnea
Breathing that is shallower or slower than normal during sleep

Hypotonia
Decreased muscle tone (temporary paralysis); Usually present during REM to prevent sleepers form acting out dreams

Hypoxemia( )
A reduced level of oxygen in the blood

Hypoxia
An abnormal condition in which the oxygen available to the body cells is inadequate to meet their metabolic needs

:E Ratio
The ratio of inspiratory to expiratory time during mechanical ventilation

Inhaler
A device for administering medicines by inhalation

Inspiratory Pause
Inspiratory pause is a brief pause (0.1 to 2 seconds) at end-inspiration during which pressure is held constant and flow is zero; The purpose of the pause is to improve gas distribution throughout the lungs; Same as plateau pressure

Inspiratory Phase
The part of the ventilatory cycle from the beginning of the inspiratory flow to the beginning of the expiratory flow; Any inspiratory pause (plateau) is included in the inspiratory phase
Inspiratory Positive Airway Pressure (IPAP)
The higher pressure used in BiPAP; Helps to assist ventilation

Inspiratory Time
The inspiratory time (expressed in seconds) is the duration of inspiration during mechanical ventilation; As inspiratory time increases, mean airway pressure increases and the I:E ratio becomes higher

Intermittent Mandatory Ventilation (IMV)
Periodic ventilation with positive pressure, with the patient breathing spontaneously between breaths

Intubation
The insertion of a tube into the patient's airway to allow mechanical ventilation

Invasive
Procedure in which the body cavity is entered by use of a tube, needle or device

Jaundice
A yellow discoloration of the skin caused by a build up of bilirubin

K Complex
A sharp, negative EEG wave followed by a high-voltage slow wave, lasting at least 0.5 second; One marker to define stage II sleep

Length of Stay (LOS)
The number of days a patient stays in the hospital; The number of days is used as a measure of cost effectiveness

Maintenance of Wakefulness Test (MWT)
Used in the assessment in the ability to remain awake; Subjects are instructed to remain awake in a darkened room in a semi-reclined position

Mandatory Breath
A breath whose inspiratory flow and/or pressure is under the control of the ventilator

Manual Breath
A breath initiated by the patient

Mean Airway Pressure (MAP)
The average pressure over one inspiration/exhalation cycle; the value displayed on a ventilator is the average of this calculation over one minute; The display is updated after each exhalation

Microsleep(s)
A period lasting up to a few seconds during which the polysomnogram suddenly shifts from waking characteristics to sleep and external stimuli are not perceived; Associated with excessive daytime sleepiness and automatic behavior

Minute Ventilation (VE)
The volume of gas that moves in and out of the lungs in one minute; It is calculated by multiplying the exhaled tidal volume by the respiratory rate

Mixed Apnea
Typically a central apnea followed by an obstructive apnea

Montage
The particular arrangement by which a number of derivations are displayed simultaneously in a polysomnogram

Multiple Sleep Latency Test (MSLT)
Test that consists of a series of short naps during the daytime, done in the sleep lab, to measure daytime sleepiness and how fast you fall asleep; Usually given to assist in diagnosing or ruling out the possibility of Narcolepsy

Muscle Tone
A term sometimes used for resting muscle potential or resting muscle activity

Myocolnus
Muscle contractions in the form of abrupt jerks or twitches generally lasting less than 100msec.

Narcolepsy
Intrusion of REM sleep into wakefulness; Onset of deepest sleep in a rapid, overwhelming fashion; The prevalence of narcolepsy has been calculated at about 0.03% of the general population

Nasal Irrigation
The process of cleaning nasal and sinus passages with saline solution (sterile salt water); Helps keep nasal and sinus passages open so they drain properly and breathing through nose is easier (i.e. RinoFlow system)

Nebulizer
A machine that makes medicine into a fine spray or aerosol so that it can be breathed into the lungs

Negative End Expiratory Pressure (NEEP)
The application of sub-atmospheric pressure to the airway during the expiratory phase of positive pressure ventilation

Negative Inspiratory Force (NIF)
The negative pressure generated during a maximally forced inspiratory effort against an obstruction to flow

Nocturnal Sleep
Indicative of the typical "nighttime," or major, sleep period dictated by one's circadian rhythm of sleep and wakefulness; The conventional time for sleeping

Non-Rapid Eye Movement Sleep (NREMS)
NREMS, also written as non-REMS made up of stages 1, 2, 3 and 4

Noninvasive
Treatment or therapy provided to patient without entering the body in any way; For example, in Noninvasive Ventilation, breathing assistance is provided by a comfortable mask, used mostly during sleep, avoiding the use of a breathing tube inserted into the throat

Noninvasive Positive Pressure Ventilation (NPPV)
Positive pressure ventilation provided without endotracheal tube intubation or tracheostomy, usually via a form fitting nasal mask
Nosocomial Pneumonia
An inflammation of the lungs from an infection acquired in the hospital

Obesity-hypoventilation Syndrome
by severe OSA and daytime hypoventilation (hypercapnia) despite relatively normal pulmonary function; Also known as Pickwickian syndrome

Obstructive Apnea
Cessation of airflow into or out of the mouth or nose although efforts to breathe continue

Obstructive Sleep Apnea (OSA)
A life threatening and life altering condition that causes a person to stop breathing repeatedly during sleep due to obstruction of the airway by excess tissue in the back of the throat; 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 amount of tissue in the uvula area

P0.1
Occlusion pressure at 0.1 second

Pallor
Having a pale color

Parasomnia
Disorder of arousal, partial arousal, or sleep stage transition such as sleepwalking

Pathological Apnea
A respiratory pause (for 10 seconds or longer in adults) that is abnormal if it is prolonged or associated with cyanosis, abrupt pallor, hypotonia or bradycardia

Peak End Expiratory Pressure(PEEP)
The application of positive pressure to the airways and alveoli during expiration when the patient is breathing with a mechanical ventilator; Maintains a small amount of air in the lungs, preventing complete emptying on exhalation to avoid airway collapse
Peak Expiratory Flow Rate(PEFR)
Also known as peak flow value; A measurement of the maximum speed with which a person can blow air out of their lungs

Peak Flow Meter
A simple, hand-held device that measures maximum expiratory breathing effort, or peak flow value

Peak Inspiratory Pressure(PIP)
The greatest airway pressure during an inspiratory cycle no matter what the breath type; The pressure is measured at the exhalation valve and the new data displayed at the beginning of exhalation

Periodic Breathing
Three or more apneic pauses of 3 or more seconds (but less than 20 seconds) in duration within periods of normal respiration of 20 seconds or less

Periodic Limb Movement Disorder(PLMS)
PLMS are characterized by leg movements or jerks which typically occur every 20 to 40 seconds during sleep, causing sleep to be disrupted and leaving the person with excessive daytime sleepiness; In most cases, the bed partner typically reports these movements; Related to Restless Leg Syndrome

Personal Best
The highest peak flow measurement you can reach consistently when your asthma is under control

Phase Advance
The shift of sleep or wake to an earlier position in the 24-hour sleep-wake cycle

Phase Delay
A shift of sleep or wake to a later time of the 24-hour sleep-wake cycle

Pickwickian
Descriptor for an obese person who snores, is sleepy, and has alveolar hypoventilation

Pneumonia
An inflammation of the lungs from an infection

Polysomnograph or Polysomnogram
A mechanical recording of a person's sleep, using many criteria such as the amount of oxygen in bloodstream, pulse, brain waves and eye movement; The continuous and simultaneous recording of physiological variables during sleep, i.e., EEG, EOG, EMG (these are the three basic stage scoring parameters), EKG, respiratory air flow, respiratory excursions, lower limb movement, and other electrophysiological variables

Pressure Control Ventilation (PCV)
Equivalent to time-triggered, pressure-limited, and time cycled ventilation

Pressure Support Ventilation (PSV)
Pressure limited assist ventilation designed to augment a spontaneously generated breath; The patient has primary control over the frequency of the breathing, the inspiratory time, and the inspiratory flow

Pressure Trigger
Initiation of inspiration when the patient's inspiratory effort exceeds the pressure sensitivity (threshold)

Proportional Assist Ventilation (PAV)
A mode of ventilatory support in which the level of mechanical assistance varies with patient demand

Pulmonary Edema
The leakage of fluid from the capillaries into the alveoli as a result of increased pressure inside the capillaries or a leaky capillary wall

REM Density
A function that expresses the frequency of eye movements per unit time during sleep stage REM

REM Sleep Latency
The interval from sleep onset to the first appearance of stage REM sleep

REM Sleep Onset

The beginning of the REM sleep episode as designated by the A Manual of Standardized Terminology; Better known as the R and K Manual

Rapid Eye Movement (REM)
A sleep state that recurs cyclically several times during a normal period of sleep; Characterized by increased neuronal activity of the forebrain and midbrain, by depressed muscle tone, and esp. in humans by dreaming, rapid eye movements, and vascular congestion of the sex organs; Also called Paradoxical Sleep or Dream Sleep

Rapid Shallow Breathing Index (f/VT)
Used to evaluate the adequacy of the patient’s spontaneous ventilation; Calculated as = f/VT = (Spont. Rate)/(Spont VE)

Resistance
Impedance to flow in a tube or a conduit; Quantified as the ratio of the difference in pressure between the two points along a tube length divided by the volumetric flow of the fluid per unit of time (cmH20/L/sec)

Respiration
The act of inhaling and exhaling air

Respiratory Disturbance Index (RDI)
The number of apneas (obstructive, central or mixed) plus hypopneas per hour of total sleep time as determined by all-night polysomnography; Synonymous with apnea-hypopnea index

Respiratory Failure, Acute
A clinical condition in which the patient’s arterial oxygen concentration drops markedly with or without an increase in carbon dioxide concentration

Respiratory Failure, Chronic
Chronic inability of the respiratory system to maintain the function of oxygenating blood and remove carbon dioxide from the lungs

Respiratory Insufficiency
Failure to adequately provide oxygen to cells of the body and to remove excess carbon dioxide from them

Response Time
A measure (usually in msec) of the speed with which a mechanical ventilator can respond to a patient’s inspiratory effort and cycle into the inspiratory phase

Restless Leg Syndrome
A discomfort in the legs which is relieved by moving or stimulating the legs; This feeling is difficult to describe and commonly referred to as a crawling, tingling or prickling sensation

Restrictive Lung Disease
A broad category of disorders with widely variable etiologies; But all resulting in a reduction in lung volumes

Rhinitis
Inflammation of the nasal mucous usually resulting in runny nose or congestion

Sawtooth Waves
A form of theta rhythm (4-7 Hz) that occurs during REM sleep and is characterized by a notched waveform

Seasonal Affective Disorder (SAD)
A seasonal disruption of mood that occurs during the winter months and ceases with the advent of spring; Symptoms usually begin in September when days begin to shorten, and last through the winter and into March when the days begin to lengthen again; Light therapy plays a big part in its origin and treatment

Sensitivity
A measure of the amount of negative pressure that must be generated by a patient in order to trigger a mechanical ventilator into the inspiratory phase

Sinusitis
An irritation or inflammation of the lining of the sinuses; When the mucous membranes lining the sinus walls become inflamed, these openings become blocked and the sinuses do not drain properly

Sleep Architecture
The NREMS/REMS stage and cycle infrastructure of sleep understood from the vantage point of the quantitative relationship of these components to each other

Sleep Cycle
Synonymous with the non-REM-REM sleep cycle

Sleep Efficiency or Sleep Efficiency Index
The proportion of sleep in the period potentially filled by sleep, that is, the ratio of total sleep time to time in bed

Sleep Hygiene
The conditions and practices that promote continuous and effective sleep; Including: Regularity of bedtime and arise time, i.e., Going to bed and getting up at the same time each day; Spend only enough time in bed to get an adequate amount of sleep, usually 8-9 hours for normal adults; Restriction of alcohol and caffeinated beverages in the period prior to bedtime; Proper exercise, nutrition, and control of environmental factors, such as noise, light and temperature so that they enhance, and not disturb, restful sleep

Sleep Latency
The period of time measured from lights out, or bedtime, to the onset of sleep

Sleep Log
A daily, written record of a person’s sleep-wake pattern, containing information such as time of retiring and arising, time in bed, etc.

Sleep Onset
The transition from waking to sleep, normally into non-REM

Sleep Paralysis
Immobility of the body that occurs in the transition from sleep to wakefulness; A partial manifestation of REM sleep

Sleep Spindle
Spindle-shaped bursts waves which are one of the identifying features of Sleep stage II

Sleep Stage I
Relatively low-voltage, mixed-frequency EEG without rapid eye movements; Slow eye movements are often present; Vertex sharp waves may be seen; EMG activity is not suppressed

Sleep Stage II
12-14 cps sleep spindles and K complexes on a background of relatively low-voltage, mixed-frequency EEG activity

Sleep Stage III
Moderate amounts (20-50%) of high-amplitude (75 uV or greater) slow-wave (2 cps or slower) EEG activity

Sleep Stage IV
Predominance (greater that 50%) of high- amplitude (75 uV or greater) slow-wave (2 cps or slower) EEG activity

Sleep-onset REM Period
The beginning of sleep by entrance directly into stage REM sleep; The onset of REM occurs within 10 minutes of sleep onset

Slow-wave Sleep
Sleep characterized by EEG waves of duration slower than 4 Hz; Synonymous with Sleep stages III and IV combined (Delta sleep)

Spacer
A small device that attaches to a metered dose inhaler medication in order to help improve the delivery of drugs to the lungs and reduce unwanted side effects such as the unpleasant taste of some drugs

Static Compliance
A measure of the distensibility of the lung (i.e., the pressure required to maintain a given volume of inflation)

Sudden Infant Death Syndrome (SIDS)
The sudden and unexplained death of an infant who has no known illness, usually under one year of age, that remains unexplained after the performance of a complete postmortem investigation, including an autopsy, an examination of the scene of death and review of the case history

Synchronous Intermittent Mandatory Ventilation (SIMV)
Periodic assisted ventilation with positive pressure, with the patient breathing spontaneously between breaths

Adult Respiratory Distress Syndrome (ARDS)
Indicates respiratory failure with life threatening distress and hypoxemia, associated with acute pulmonary injuries

Tachycardia
An abnormal increase in heart rate above an age-specified rate

Tachypnea
An elevated respiratory rate

Theta Activity
EEG activity with a frequency of 4-7 Hz, generally maximal over the central and temporal cortex

Tidal Volume (VT)
The amount of air passing in and out of the lung during and normal resting breath

Time Constant
A mathematical expression describing the relative efficacy of lung unit filling and emptying, and computed as the product of compliance times resistance, with a resulting measure in seconds

Total Recording Time
The interval from the beginning of the sleep recording to the end of the sleep recording

Total Sleep Period (sleep period time)
The period of time measured from sleep onset to final awakening; In addition to the total sleep time, it is comprised of the time taken up by arousals and movement time until wake-up

Total Sleep Time (TST)
The amount of actual sleep time in a sleep period; Equal to the total sleep period less movement and awake time; Total sleep time is the total of all REMS and N-REMS in a sleep period

Tracheostomy
An artificial opening in the trachea that facilitates the passage of air or removal of secretions

Trigger
Irritants or allergens found both indoors and outdoors that make it difficult to keep asthma under control; As pertaining to mechanical ventilation; Normally a patient effort to begin inhalation

Ventilator
A mechanical device for artificial ventilation of the lungs

Vertex Sharp Wave
Sharp negative wave usually seen in later portion of Sleep Stage I

Viral Pneumonia ( )
An inflammation and infection caused by a virus

Vital Capacity (VC)
The total amount of air that can be exhaled after a maximum inspiration; The sum of the inspiratory reserve volume, the tidal volume, and the expiratory reserve volume

Volume
Space occupied by matter measured in milliliters or liters

Wake Time
The total time scored as wakefulness in a polysomnogram occurring between sleep onset and the final wake-up

Wheezing
A musical whistling sound caused by narrowing of the airway

Work of Breathing
An objective of the depth and rate of respirations

Zeitgeber
German term for an environmental time cue that usually helps entrainment to the 24-hour day, such as sunlight, noise, social interaction, etc.

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