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Acute Lung Injury
A precursor to ARDS, lesser level of injury, severe oxygenation abnormality presence of diffuse parenchymal infiltrates on chest x-ray (three or four quadrants), hypoxemia as manifested by a PaO2/FiO2 (fraction of inspired oxygen) ratio of <300 torr, and a pulmonary capillary wedge pressure of <18 mmHg, or no clinical evidence of elevated left-sided heart filling pressure.

Adult or Acute Respiratory Distress Syndrome
Same criteria as acute lung injury (ALI) except more profound severe oxygenation abnormality with a PaO2/FiO2 ratio of <200 torr.  The pathophysiology of ARDS is characterized by a cascading effect in a proinflammatory response by the body.  For more information and discussion see FAQs (Frequently Asked Questions), Articles and Information in Learn About ARDS Section 1, and brief overview in What Is? Section.

Affection
Feeling or emotion, one of the three aspects of the mind, the others being conation (willing or desiring), and cognition (awareness). They may work as a whole, but any one may dominate any mental process.

Air bed
A specially designed air–filled floating mattress bed designed to prevent development and/or alleviate and facilitate healing of bed sores and certain physical problems associated with long term restriction to bed, especially in a paralyzed and/or coma state.

Air leak syndromes
A spectrum of diseases with the same underlying pathophysiology. Air leaks involve overdistension of the alveolar sacs or terminal airways, leading to disruption of airway integrity and dissection of air into the surrounding spaces. The pulmonary air leak syndromes include pneumomediastinum, pneumothorax, pulmonary interstitial emphysema, and pneumopericardium.

Alveolar-arterial oxygen gradient (A-a DO2)
The difference between the amount of oxygen in the arterial blood and the amount of oxygen actually delivered to the lungs. Normally this value is less than 100 Hg but in the context of severe respiratory disease it may exceed 600 mm Hg.

Alveolitis
Inflammation of the alveoli.

Alveolus (sg.), Alveoli (pl.)
The tiny spherical air exchange sacs in the lung, located at the ends of your smallest airways (bronchiole). The alveoli are surrounded by capillaries (small blood vessels), which are the blood vessels bringing blood into interior of the lung that is depleted in oxygen. The exchange of oxygen and carbon dioxide takes place through a membrane separating the alveoli and capillaries.  The alveoli are lined with and supported by tissue called the interstitium.

Amnesia
Partial or complete memory loss due to some precursor event.   anterograde amnesia–loss of memory of recent events after the event; retrograde amnesia–loss of memory for past events before the event.

Ante or antero
Prefix meaning before or in front of, e.g. anterior (in front of, the front surface of)

Aplasia
Incomplete development of tissue, absence of growth.

Aplastic
Incapable of growing new tissue.

Arterial Blood Gas Test
The test that tells the health professional how your lungs are working. It is very sensitive to changes in breathing patterns and is used to establish treatment for your condition and qualify for home oxygen therapy.  The main function of the lung is to bring fresh oxygen to the body tissues and get rid of carbon dioxide.  The arterial oxygen and carbon dioxide pressure levels are measured in millimeters of mercury.  The percent of oxygen that is carried in the blood is also measured. The pH tells us if the blood has too much of the acid component (carbon dioxide) or too much base (bicarbonate).

Arterial oxygen tension (PaO2)
The partial pressure of arterial oxygen.

Aspiration
Generally, the act of drawing in air/to breathe (inspiration); often more specifically means inhaling (inspiration) of stomach contents which have been projected back up through the esophagus and into the mouth and/or throat, or other foreign substances (smoke inhalation particulate matter). Aspiration is one of the three leading precipitating factors in ARDS cases.

Asthma
An obstructive lung disease that is characterized by airway narrowing and spasm. Wheezing is often heard as the air tries to move through constricted airways.   In between asthma attacks, a person may have perfectly normal lung function values. Once an attack starts, flow rate values (speed at which air moves through the lung) will be greatly reduced. Peak flow meters can monitor your flow rate daily so you will be warned of any decrease in flow rates before you feel symptoms. Your airways are very sensitive and many things can bring on an attack, such as irritants in the air, allergies and emotions. Once you can identify those things that will trigger your airways to go into spasm, you will be able to avoid them!

Atelectasis
No air in the alveoli, lung solid.

Atonic
Without tone; weak (atonia, atony, atonicity).


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