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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.

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