Inspiratory Capacity: The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration. It is the sum of the TIDAL VOLUME and the INSPIRATORY RESERVE VOLUME. Common abbreviation is IC.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.Dyspnea: Difficult or labored breathing.Lung Volume Measurements: Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.Bronchodilator Agents: Agents that cause an increase in the expansion of a bronchus or bronchial tubes.Pulmonary Disease, Chronic Obstructive: A disease of chronic diffuse irreversible airflow obstruction. Subcategories of COPD include CHRONIC BRONCHITIS and PULMONARY EMPHYSEMA.Vital Capacity: The volume of air that is exhaled by a maximal expiration following a maximal inspiration.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.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.Scopolamine Derivatives: Analogs or derivatives of scopolamine.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.Functional Residual Capacity: The volume of air remaining in the LUNGS at the end of a normal, quiet expiration. It is the sum of the RESIDUAL VOLUME and the EXPIRATORY RESERVE VOLUME. Common abbreviation is FRC.Spirometry: Measurement of volume of air inhaled or exhaled by the lung.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.Exercise Tolerance: The exercise capacity of an individual as measured by endurance (maximal exercise duration and/or maximal attained work load) during an EXERCISE TEST.Pulmonary Ventilation: The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.Tidal Volume: The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are TV or V with subscript T.Exercise Test: Controlled physical activity which is performed in order to allow assessment of physiological functions, particularly cardiovascular and pulmonary, but also aerobic capacity. Maximal (most intense) exercise is usually required but submaximal exercise is also used.Plethysmography: Recording of change in the size of a part as modified by the circulation in it.Diaphragm: The musculofibrous partition that separates the THORACIC CAVITY from the ABDOMINAL CAVITY. Contraction of the diaphragm increases the volume of the thoracic cavity aiding INHALATION.Ethanolamines: AMINO ALCOHOLS containing the ETHANOLAMINE; (-NH2CH2CHOH) group and its derivatives.Respiratory Muscles: These include the muscles of the DIAPHRAGM and the INTERCOSTAL MUSCLES.Administration, Inhalation: The administration of drugs by the respiratory route. It includes insufflation into the respiratory tract.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Cross-Over Studies: Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)Exercise: Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure.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.