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Maximal Expiratory Flow Rate: The airflow rate measured during the first liter expired after the first 200 ml have been exhausted during a FORCED VITAL CAPACITY determination. Common abbreviations are MEFR, FEF 200-1200, and FEF 0.2-1.2.Peak Expiratory Flow Rate: Measurement of the maximum rate of airflow attained during a FORCED VITAL CAPACITY determination. Common abbreviations are PEFR and PFR.Forced Expiratory Flow Rates: The rate of airflow measured during a FORCED VITAL CAPACITY determination.Maximal Expiratory Flow-Volume Curves: Curves depicting MAXIMAL EXPIRATORY FLOW RATE, in liters/second, versus lung inflation, in liters or percentage of lung capacity, during a FORCED VITAL CAPACITY determination. Common abbreviation is MEFV.Vital Capacity: The volume of air that is exhaled by a maximal expiration following a maximal inspiration.Residual Volume: The volume of air remaining in the LUNGS at the end of a maximal expiration. Common abbreviation is RV.Forced Expiratory Volume: Measure of the maximum amount of air that can be expelled in a given number of seconds during a FORCED VITAL CAPACITY determination . It is usually given as FEV followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity.Respiratory Function Tests: Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.Lung Volume Measurements: Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.Total Lung Capacity: The volume of air contained in the lungs at the end of a maximal inspiration. It is the equivalent to each of the following sums: VITAL CAPACITY plus RESIDUAL VOLUME; INSPIRATORY CAPACITY plus FUNCTIONAL RESIDUAL CAPACITY; TIDAL VOLUME plus INSPIRATORY RESERVE VOLUME plus functional residual capacity; or tidal volume plus inspiratory reserve volume plus EXPIRATORY RESERVE VOLUME plus residual volume.Spirometry: Measurement of volume of air inhaled or exhaled by the lung.Airway Obstruction: Any hindrance to the passage of air into and out of the lungs.Asthma: A form of bronchial disorder with three distinct components: airway hyper-responsiveness (RESPIRATORY HYPERSENSITIVITY), airway INFLAMMATION, and intermittent AIRWAY OBSTRUCTION. It is characterized by spasmodic contraction of airway smooth muscle, WHEEZING, and dyspnea (DYSPNEA, PAROXYSMAL).Airway Resistance: Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow.Pulmonary Ventilation: The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Respiratory Mechanics: The physical or mechanical action of the LUNGS; DIAPHRAGM; RIBS; and CHEST WALL during respiration. It includes airflow, lung volume, neural and reflex controls, mechanoreceptors, breathing patterns, etc.Albuterol: A short-acting beta-2 adrenergic agonist that is primarily used as a bronchodilator agent to treat ASTHMA. Albuterol is prepared as a racemic mixture of R(-) and S(+) stereoisomers. The stereospecific preparation of R(-) isomer of albuterol is referred to as levalbuterol.Bronchodilator Agents: Agents that cause an increase in the expansion of a bronchus or bronchial tubes.Administration, Inhalation: The administration of drugs by the respiratory route. It includes insufflation into the respiratory tract.Ipratropium: A muscarinic antagonist structurally related to ATROPINE but often considered safer and more effective for inhalation use. It is used for various bronchial disorders, in rhinitis, and as an antiarrhythmic.Beclomethasone: An anti-inflammatory, synthetic glucocorticoid. It is used topically as an anti-inflammatory agent and in aerosol form for the treatment of ASTHMA.Nebulizers and Vaporizers: Devices that cause a liquid or solid to be converted into an aerosol (spray) or a vapor. It is used in drug administration by inhalation, humidification of ambient air, and in certain analytical instruments.Lung Diseases, Obstructive: Any disorder marked by obstruction of conducting airways of the lung. AIRWAY OBSTRUCTION may be acute, chronic, intermittent, or persistent.Atropine Derivatives: Analogs and derivatives of atropine.Asthma, Exercise-Induced: Asthma attacks following a period of exercise. Usually the induced attack is short-lived and regresses spontaneously. The magnitude of postexertional airway obstruction is strongly influenced by the environment in which exercise is performed (i.e. inhalation of cold air during physical exertion markedly augments the severity of the airway obstruction; conversely, warm humid air blunts or abolishes it).Aerosols: Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents.Anti-Asthmatic Agents: Drugs that are used to treat asthma.Terbutaline: A selective beta-2 adrenergic agonist used as a bronchodilator and tocolytic.Double-Blind Method: A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment.Maximal Midexpiratory Flow Rate: Measurement of rate of airflow over the middle half of a FORCED VITAL CAPACITY determination (from the 25 percent level to the 75 percent level). Common abbreviations are MMFR and FEF 25%-75%.Bronchitis: Inflammation of the large airways in the lung including any part of the BRONCHI, from the PRIMARY BRONCHI to the TERTIARY BRONCHI.Dust: Earth or other matter in fine, dry particles. (Random House Unabridged Dictionary, 2d ed)Bronchial Provocation Tests: Tests involving inhalation of allergens (nebulized or in dust form), nebulized pharmacologically active solutions (e.g., histamine, methacholine), or control solutions, followed by assessment of respiratory function. These tests are used in the diagnosis of asthma.Respiration Disorders: Diseases of the respiratory system in general or unspecified or for a specific respiratory disease not available.Budesonide: A glucocorticoid used in the management of ASTHMA, the treatment of various skin disorders, and allergic RHINITIS.Respiratory Tract DiseasesRespiration: The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).Pregnenediones: Unsaturated pregnane derivatives containing two keto groups on side chains or ring structures.Cough: A sudden, audible expulsion of air from the lungs through a partially closed glottis, preceded by inhalation. It is a protective response that serves to clear the trachea, bronchi, and/or lungs of irritants and secretions, or to prevent aspiration of foreign materials into the lungs.Expiratory Reserve Volume: The extra volume of air that can be expired with maximum effort beyond the level reached at the end of a normal, quiet expiration. Common abbreviation is ERV.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Respiratory Sounds: Noises, normal and abnormal, heard on auscultation over any part of the RESPIRATORY TRACT.