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Vital capacity (VC) is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. It is approximately equal to Forced Vital Capacity (FVC). [1] [2] A person's vital capacity can be measured by a wet or regular spirometer.
Lung volumes and lung capacities are measures of the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air. [1] Tidal breathing is normal, resting breathing; the tidal volume is the volume of air that is inhaled or exhaled in only a single such ...
A lung's capacity consists of two or more lung volumes. The lung volumes are tidal volume (V T), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV). The four lung capacities are total lung capacity (TLC), inspiratory capacity (IC), functional residual capacity (FRC) and vital capacity (VC).
TLC: Total lung capacity: the volume in the lungs at maximal inflation, the sum of VC and RV. TV: Tidal volume: that volume of air moved into or out of the lungs in 1 breath (TV indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol TV or V T is used.)
Vital capacity: the volume of air breathed out after the deepest inhalation. V T: Tidal volume: that volume of air moved into or out of the lungs during quiet breathing (VT indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol TV or V T is used.) FRC
The FEV1/FVC ratio, also called modified Tiffeneau-Pinelli index, [1] is a calculated ratio used in the diagnosis of obstructive and restrictive lung disease. [2] [3] It represents the proportion of a person's vital capacity that they are able to expire in the first second of forced expiration to the full, forced vital capacity (). [4]
Lung volumes. Functional residual capacity (FRC) is the volume of air present in the lungs at the end of passive expiration. [1] At FRC, the opposing elastic recoil forces of the lungs and chest wall are in equilibrium and there is no exertion by the diaphragm or other respiratory muscles. [1]
Lung capacity can be increased by physical training as much as 40% but the effect may be modified by exposure to air pollution. [103] [104] Other lung function tests include spirometry, measuring the amount (volume) and flow of air that can be inhaled and exhaled. The maximum volume of breath that can be exhaled is called the vital capacity.