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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.
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.)
Measurement of maximal inspiratory and expiratory pressures is indicated whenever there is an unexplained decrease in vital capacity or respiratory muscle weakness is suspected clinically. Maximal inspiratory pressure (MIP) is the maximal pressure that can be produced by the patient trying to inhale through a blocked mouthpiece.
The tidal volume, vital capacity, inspiratory capacity and expiratory reserve volume can be measured directly with a spirometer. These are the basic elements of a ventilatory pulmonary function test. Determination of the residual volume is more difficult as it is impossible to "completely" breathe out.
He also completed accurate measures of other volume parameters by using his "Expirator". Some of the parameters he described are used today, including residual volume and vital capacity. 1846 The water spirometer measuring vital capacity was developed by a surgeon named John Hutchinson. He invented a calibrated bell inverted in water, which was ...
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.)
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]
The helium dilution technique is the way of measuring the functional residual capacity of the lungs (the volume left in the lungs after normal expiration). This technique is a closed-circuit system where a spirometer is filled with a mixture of helium (He) and oxygen. The amount of He in the spirometer is known at the beginning of the test ...