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Glossary of Terms and Acronyms

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A

Air spaces: All alveolar ducts, alveolar sacs, and alveoli. To be contrasted with AIRWAYS.

Airways: All passageways of the respiratory tract from mouth or nose down to and including respiratory bronchioles. To be contrasted with AIR SPACES.

Allergen: A material that, as a result of coming into contact with appropriate tissues of an animal body, induces a state of allergy or hypersensitivity; generally associated with idiosyncratic hypersensitivities.

Alveolus: Hexagonal or spherical air cells of the lungs. The majority of alveoli arise from the alveolar ducts that are lined with the alveoli. An alveolus is an ultimate respiratory unit where the gas exchange takes place.

Asthma: A disease characterized by an increased responsiveness of the airways to various stimuli and manifested by slowing of forced expiration which changes in severity either spontaneously or as a result of therapy. The term asthma may be modified by words or phrases indicating its etiology, factors provoking attacks, or its duration.

Atropine: A poisonous white crystalline alkaloid, C17H23NO3, from belladonna and related plants, used to relieve spasms of smooth muscles. It is an anticholinergic agent.

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B

BAL: Bronchoalveolar lavage.

Beta-adrenergic agonist medication: A bronchodilator medicine that opens the airways by relaxing the muscles around the airways that may tighten during an asthma attack or in COPD (chronic obstructive pulmonary disease). Opening (dilating) airways helps to relieve shortness of breath. Beta-agonists can be administered by inhalers or orally. Albuterol is an example of a beta-agonist.

Breathing pattern: A general term designating the characteristics of the ventilatory activity, e.g., tidal volume, frequency of breathing, and shape of the volume time curve.

Bronchiole: One of the finer subdivisions of the airways, less than 1 mm in diameter, and having no cartilage in its wall.

Bronchiolitis: Inflammation of the bronchioles that may be acute or chronic. If the etiology is known, it should be stated. If permanent occlusion of the lumens is present, the term bronchiolotis obliterans may be used.

Bronchitis: A non-neoplastic disorder of structure or function of the bronchi resulting from infectious or noninfectious irritation. The term bronchitis should be modified by appropriate words or phrases to indicate its etiology, its chronicity, the presence of associated airways dysfunction, or type of anatomic change. The term chronic bronchitis, when unqualified, refers to a condition associated with prolonged exposure to nonspecific bronchial irritants and accompanied by mucous hypersecretion and certain structural alterations in the bronchi. Anatomic changes may include hypertrophy of the mucous-secreting apparatus and epithelial metaplasia, as well as more classic evidences of inflammation. In epidemiologic studies, the presence of cough or sputum production on most days for at least three months of the year has sometimes been accepted as a criterion for the diagnosis.

Bronchoalveolar lavage (BAL)): A clinical technique which removes cell samples from the lower lungs to allow assessment of inflammation and other respiratory conditions.

Bronchoconstrictor: An agent that causes a reduction in the caliber (diameter) of airways.

Bronchodilator: An agent that causes an increase in the caliber (diameter) of airways.

Bronchus: One of the subdivisions of the trachea serving to convey air to and from the lungs. The trachea divides into right and left main bronchi, which in turn form lobar, segmental, and subsegmental bronchi.

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C

Chronic obstructive pulmonary disease (COPD)): This term refers to chronic lung disorders that result in blocked air flow in the lungs. The two main COPD disorders are emphysema and chronic bronchitis, the most common causes of respiratory failure. Emphysema occurs when the walls between the lung's air sacs become weakened and collapse. Damage from COPD is usually permanent and irreversible.

COPD: Chronic obstructive pulmonary disease.

Cytoplasm: The organized complex of inorganic and organic substances external to the nucleus of a cell including fluid and organelles (specialized parts of the cell that are analogous to organs, e.g., mitochondria or ribosomes).

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D

Daily Mortality: Deaths on any one day.

Decrements in lung function: Decreases in lung function that can be measured by spirometry.

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E

ELF: Epithelial lining fluid.

Epithelium: A membranous cellular tissue that covers a free surface or lines a tube or cavity of an animal body and serves especially to enclose and protect the other parts of the body, to produce secretions and excretions, and to function in assimilation.

Epidemiology: A branch of medical science that deals with the incidence, distribution, and control of disease in a population.

Eosinophil: A white blood cell that contains intracytoplasmic granules that are readily stained by eosin, a red fluorescent dye.

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F

FEFx: Forced expiratory flow.

FEV: Forced expiratory volume.

FEVt /FVC: A ratio of timed (t = 0.5, 1, 2, 3 s) forced expiratory volume (FEVt) to forced vital capacity (FVC). The ratio is often expressed in percent 100 x FEVt /FVC. It is an index of airway obstruction.

FIVC: Forced inspiratory vital capacity.

Flow volume curve: Graph of instantaneous forced expiratory flow recorded at the mouth, against corresponding lung volume. When recorded over the full vital capacity, the curve includes maximum expiratory flow rates at all lung volumes in the VC range and is called a maximum expiratory flow-volume curve (MEFV). A partial expiratory flow-volume curve (PEFV) is one which describes maximum expiratory flow rate over a portion of the vital capacity only.

Forced expiratory flow (FEFx)): Related to some portion of the FVC curve. Modifiers refer to the amount of the FVC already exhaled when the measurement is made. For example:

FEF75% = instantaneous forced expiratory flow after 75% of the FVC has been exhaled.

FEF200-1200 = mean forced expiratory flow between 200 ml and 1200 ml of the FVC (formerly called the maximum expiratory flow rate (MEFR).

FEF25-75% = mean forced expiratory flow during the middle half of the FVC [formerly called the maximum mid-expiratory flow rate (MMFR)].

FEFmax = the maximum forced expiratory flow achieved during an FVC.

Forced expiratory volume (FEV): Denotes the volume of gas that is exhaled in a given time interval during the execution of a forced vital capacity. Conventionally, the times used are 0.5, 0.75, or 1 sec, symbolized FEV0.5, FEV0.75, FEV1. These values are often expressed as a percent of the forced vital capacity, e.g. (FEV1 /VC) x 100.

Forced inspiratory vital capacity (FIVC): The maximal volume of air inspired with a maximally forced effort from a position of maximal expiration.

Forced vital capacity (FVC): Vital capacity performed with a maximally forced expiratory effort.

FRC: Functional residual capacity.

Functional residual capacity (FRC): The sum of RV and ERV (the volume of air remaining in the lungs at the end-expiratory position). The method of measurement should be indicated as with RV.

FVC: Forced vital capacity.

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G

Gas exchange:Movement of oxygen from the alveoli into the pulmonary capillary blood as carbon dioxide enters the alveoli from the blood. In broader terms, the exchange of gases between alveoli and lung capillaries.

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H

HDM: House dust mite.

Histamine: Derived from the amino acid histidine and found in all body tissues, with the highest concentration in the lung; a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, and a vasodilator that causes a fall in blood pressure. Histamine is stored and released from mast cells and contributes to the inflammatory response.

House dust mite (HDM): Either of two widely distributed mites of the genus Dermatophagoides (D. farinae and D. pteronyssinus) that commonly occur in house dust and often induce allergic responses, especially in children.

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I

IC: Inspiratory capacity.

Immunoglobulin: A class of proteins produced in lymph tissue in vertebrates that function as antibodies in the immune response.

Induction of asthma: The process of lung sensitization and respiratory inflammation resulting in increased difficulty with breathing; it can be caused by a variety of external stimuli (e.g., pollens, air pollutants, viruses, animal hair, mites, and roach feces).

Inspiratory capacity (IC): The sum of IRV and TV.

Inspiratory reserve volume (IRV): The maximal volume of air inhaled from the end-inspiratory level.

Inspiratory vital capacity (IVC): The maximum volume of air inhaled from the point of maximum expiration.

Interstitium: A small area, space, or gap in the substance of an organ or tissue.

IRV: Inspiratory reserve volume.

IVC: Inspiratory vital capacity.

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J

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K

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L

Lung volume (VL): Actual volume of the lung, including the volume of the conducting airways.

Lymphocyte: A variety of white blood cell produced in lymphoid tissues and lymphatic glands of the body. Lymphocytes have a number of very important roles in the immune system including the production of antibodies and other substances that fight infection and disease.

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M

Maximal aerobic capacity (max VO2)): The rate of oxygen uptake by the body during repetitive maximal respiratory effort. Synonymous with maximal oxygen consumption.

Maximum breathing capacity (MBC): Maximal volume of air that can be breathed per minute by a subject breathing as quickly and as deeply as possible. This tiring lung function test is usually limited to 12-20 sec, but given in liters (BTPS)/min. Synonymous with maximum voluntary ventilation (MVV).

Maximum expiratory flow (Vmax x): Forced expiratory flow, related to the total lung capacity or the actual volume of the lung at which the measurement is made. Modifiers refer to the amount of lung volume remaining when the measurement is made. For example:

Vmax 75% = instantaneous forced expiratory flow when the lung is at 75% of its TLC.

Vmax 3.0 = instantaneous forced expiratory flow when the lung volume is 3.0 liters.

Maximum expiratory flow rate (MEFR): Synonymous with FEF200-1200.

Maximum mid-expiratory flow rate (MMFR or MMEF): Synonymous with FEF25-75%.

Maximum ventilation (max VE): The volume of air breathed in one minute during repetitive maximal respiratory effort. Synonymous with maximum ventilatory minute volume.

Maximum voluntary ventilation (MVV): The volume of air breathed by a subject during voluntary maximum hyperventilation lasting a specific period of time. Synonymous with maximum breathing capacity (MBC).

Max VE: Maximum ventilation.

Max VO2: Maximal aerobic capacity.

MBC: Maximum breathing capacity.

MEFR: Maximum expiratory flow rate.

Minute ventilation (VE): Volume of air breathed in one minute. It is a product of tidal volume (VT) and breathing frequency (fB). See VENTILATION.

Minute volume: Synonymous with minute ventilation.

MMFR or MMEF: Maximum mid-expiratory flow rate.

Mucociliary transport: The process by which mucus is transported, by ciliary action, from the lungs.

Mucus: The clear, viscid secretion of mucous membranes, consisting of mucin, epithelial cells, leukocytes, and various inorganic salts suspended in water.

MVV: Maximum voluntary ventilation.

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N

Nasopharyneal: Relating to the nose or the nasal cavity and the pharynx (throat).

Nitrogen oxides (NOx): Compounds of nitrogen (N) and oxygen (O) in ambient air; i.e., nitric oxide (NO) and others with a higher oxidation state of N, of which NO2 is the most important toxicologically.

NOx: Nitrogen oxides.

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O

Oxidant: A chemical compound that has the ability to remove, accept, or share electrons from another chemical species, thereby oxidizing it.

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P

PAN: Peroxyacetyl nitrate.

Particle pollution: Particle pollution (also known as “particulate matter”) consists of a mixture of solids and liquid droplets. Some particles are emitted directly; others form when pollutants emitted by various sources react in the atmosphere.

Particles: Fine solids such as dust, smoke, fumes, or smog, found in the air or in emissions.

Parts per billion (ppb): A unit commonly used to express a concentration ratio (proportion) equal to 10-9 As an example, 60 ppb is equal to 0.06 ppm.

Parts per million (ppm): A unit commonly used to express a concentration ratio (proportion) equal to 10-6. As an example, 0.06 ppm is equal to 60 ppb.

Pathogen: Any virus, microorganism, or etiologic agent causing disease.

Peak expiratory flow (PEF): The highest forced expiratory flow measured with a peak flow meter.

PEF: Peak expiratory flow.

Peroxyacetyl nitrate (PAN): Pollutant created by action of UV component of sunlight on hydrocarbons and NOx in the air; an ingredient of photochemical smog.

Plethysmograph: A rigid chamber placed around a living structure for the purpose of measuring changes in the volume of the structure. In respiratory measurements, the entire body is ordinarily enclosed ("body plethysmograph") and the plethysmograph is used to measure changes in volume of gas in the system produced 1) by solution and volatilization (e.g., uptake of foreign gases into the blood), 2) by changes in pressure or temperature (e.g., gas compression in the lungs, expansion of gas upon passing into the warm, moist lungs), or 3) by breathing through a tube to the outside. Three types of plethysmograph are used: a) pressure, b) volume, and c) pressure-volume. In type a, the body chambers have fixed volumes and volume changes are measured in terms of pressure change secondary to gas compression (inside the chamber, outside the body). In type b, the body chambers serve essentially as conduits between the body surface and devices (spirometers or integrating flowmeters) which measure gas displacements. Type c combines a and b by appropriate summing of chamber pressure and volume displacements.

PMN: Polymorphonuclear leukocyte.

PPB: Parts per billion.

PPM: Parts per million.

Polymorphonuclear leukocyte (PMN): One of several types of white blood cells that is involved in the inflammatory response following ozone-induced cell damage.

Pulmonary edema: An accumulation of excessive amounts of fluid in the lung extravascular tissue and air spaces.

Pulmonary emphysema: An abnormal, permanent enlargement of the air spaces distal to the terminal nonrespiratory bronchiole, accompanied by destructive changes of the alveolar walls and without obvious fibrosis. The term emphysema may be modified by words or phrases to indicate its etiology, its anatomic subtype, or any associated airways dysfunction.

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Q

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R

R: Resistance flow.

Residual volume (RV): That volume of air remaining in the lungs after maximal exhalation. The method of measurement should be indicated in the text or, when necessary, by appropriate qualifying symbols.

Resistance flow (R): The ratio of the flow-resistive components of pressure to simultaneous flow, in cm H2O/liter per sec. Flow-resistive components of pressure are obtained by subtracting any elastic or inertial components, proportional respectively to volume and volume acceleration. Most flow resistances in the respiratory system are nonlinear, varying with the magnitude and direction of flow, with lung volume and lung volume history, and possibly with volume acceleration. Accordingly, careful specification of the conditions of measurement is necessary.

Respiratory cycle: A respiratory cycle is constituted by the inspiration followed by the expiration of a given volume of gas, called tidal volume. The duration of the respiratory cycle is the respiratory or ventilatory period, whose reciprocal is the ventilatory frequency.

Respiratory frequency (fR): The number of breathing cycles per unit of time. Synonymous with breathing frequency (fB).

RV: Residual volume.

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S

SEM: Standard error of the mean.

Shunt: Vascular connection between circulatory pathways so that venous blood is diverted into vessels containing arterialized blood (right-to-left shunt, venous admixture) or vice versa (left-to-right shunt). Right-to-left shunt within the lung, heart, or large vessels due to malformations are more important in respiratory physiology. Flow from left to right through a shunt should be marked with a negative sign.

Specific airway conductance (Sgaw): Airway conductance divided by the lung volume at which it was measured, i.e., normalized airway conductance. SGaw = Gaw/TGV.

Specific airway resistance (SRaw): Airway resistance multiplied by the volume at which it was measured. SRaw = Raw x TGV.

Spirometry: A medical test that measures how well the lungs exhale. The information gathered during this test is useful in diagnosing certain types of lung disorders, but it is most useful when assessing for obstructive lung diseases (especially asthma and chronic obstructive pulmonary disease (COPD)). In a spirometry test, a person breathes into a mouthpiece that is connected to an instrument called a spirometer. The spirometer records the amount and the rate of air that is breathed in and out over a specified time. Some of the test measurements are obtained by normal, quiet breathing, and other tests require forced inhalation or exhalation after a deep breath.

Sputum: Expectorated matter; saliva mixed with discharges from the respiratory passages.

Standard error of the mean (SEM): An estimate of the standard deviation of the sampling distribution of means, based on the data from one or more random samples.

Stratosphere: The portion of the atmosphere approximately 6 to 30 miles above the earth's surface.

Sulfur dioxide (SO2): Colorless gas with pungent odor, released primarily from burning of fossil fuels, such as coal, containing sulfur.

Synergism: A relationship in which the combined action or effect of two or more components is greater than the sum of effects when the components act separately.

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T

Tidal volume (TV): That volume of air inhaled or exhaled with each breath during quiet breathing, used only to indicate a subdivision of lung volume. When tidal volume is used in gas exchange formulations, the symbol VT should be used.

TLC: Total lung capacity.

Total lung capacity (TLC): The sum of all volume compartments or the volume of air in the lungs after maximal inspiration. The method of measurement should be indicated, as with RV.

Trachea: Commonly known as the windpipe, a cartilaginous air tube extending from the larynx (voice box) into the thorax (chest) where it divides into left and right branches.

Troposphere: The layer of the atmosphere closest to the earth's surface.

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U

Ultraviolet (UV) radiation: A portion of the electromagnetic spectrum with wavelengths shorter than visible light. The sun produces UV, which is commonly split into three bands: UVA, UVB, and UVC. UVA is not absorbed by ozone. UVB is mostly absorbed by ozone, although some reaches the Earth. UVC is completely absorbed by ozone and normal oxygen.

UV: Ultraviolet radiation.

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V

VA: Ventilation, alveolar.

VC: Vital capacity.

Ventilation: Physiological process by which gas is renewed in the lungs. The word ventilation sometimes designates ventilatory flow rate (or ventilatory minute volume) which is the product of the tidal volume by the ventilatory frequency. Conditions are usually indicated as modifiers; i.e.,

VE = Expired volume per minute (BTPS),
     and
VI = Inspired volume per minute (BTPS).

Ventilation is often referred to as "total ventilation" to distinguish it from "alveolar ventilation" (see VENTILATION, ALVEOLAR).

Ventilation, alveolar (VA): Physiological process by which alveolar gas is completely removed and replaced with fresh gas. Alveolar ventilation is less than total ventilation because when a tidal volume of gas leaves the alveolar spaces, the last part does not get expelled from the body but occupies the dead space, to be reinspired with the next inspiration. Thus the volume of alveolar gas actually expelled completely is equal to the tidal volume minus the volume of the dead space. This truly complete expiration volume times the ventilatory frequency constitutes the alveolar ventilation.

Vital capacity (VC): The maximum volume of air exhaled from the point of maximum inspiration.

VL: Lung volume.

Vmax x: Maximum expiratory flow.

VOC: Volatile organic compound.

Volatile organic compound (VOC): Any organic compound that participates in atmospheric photochemical reactions except those designated by EPA as having negligible photochemical reactivity.

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W

Wood Smoke: Smoke is made up of a complex mixture of gases and fine, microscopic particles produced when wood and other organic matter burn. The biggest health threat from wood smoke comes from fine particles (also called particulate matter).

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