Explanation of common test values in spirometric tests

Explanation of common test values in spirometric tests[1] Abbreviation Name Description

FVC Forced Vital Capacity This is the volume of air that can forcibly be blown out after full inspiration, measured in liters.

FEV1 Forced Expiratory Volume in 1 Second This is the maximum volume of air that can forcibly blow out in the first second during the FVC manoeuvre, measured in liters. Along with FVC it is considered one of the primary indicators of lung function.

FEV1/FVC FEV1% This is the ratio of FEV1 to FVC. In healthy adults this should be approximately 75–80%. In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV1 is diminished because of increased airway resistance to expiratory flow and the FVC may be increased (for instance by air trapping in emphysema). This generates a reduced value (<80%, often ~45%). In restrictive diseases (such as pulmonary fibrosis) the FEV1 and FVC are both reduced proportionally and the value may be normal or even increased as a result of decreased lung compliance.

PEF Peak Expiratory Flow This is the maximal flow (or speed) achieved during the maximally forced expiration initiated at full inspiration, measured in liters per second.

FEF 25–75% or 25–50% Forced Expiratory Flow 25–75% or 25–50% This is the average flow (or speed) of air coming out of the lung during the middle portion of the expiration (also sometimes referred to as the MMEF, for maximal mid-expiratory flow). In small airway diseases such as asthma this value will be reduced, perhaps <65% of expected value. This may be the first sign of small airway disease detectable.

FIF 25–75% or 25–50% Forced Inspiratory Flow 25–75% or 25–50% This is similar to FEF 25–75% or 25–50% except the measurement is taken during inspiration.

FET Forced Expiratory Time This measures the length of the expiration in seconds.
SVC Slow Vital capacity Maximum volume of air that can be exhaled slowly after slow maximum inhalation.

TV Tidal volume During the normal, tidal breathing a specific volume of air is drawn into and then expired out of the lungs. This volume is tidal volume.

TLC Total Lung Capacity Maximum volume of air present in the lungs. Effectively the Vital Capacity plus residual volume.

DLCO Diffusing Capacity The carbon monoxide uptake from a single inspiration in a standard time (usually 10 sec). This will pick up diffusion impairments, for instance in pulmonary fibrosis. This must be corrected for anemia (because rapid CO diffusion is dependent on hemoglobin in RBC's a low hemoglobin concentration, anemia, will reduce DLCO) and pulmonary hemorrhage (excess RBC's in the interstitium or alveoli can absorb CO and artificially increase the DLCO capacity).
MVV Maximum Voluntary Ventilation A measure of the maximum amount of air that can be inhaled and exhaled in one minute, measured in liters/minute