Forced Vital Capacity (FVC) - The volume of air
expelled by a forced maximal expiration from a position of maximal
Forced Expiratory Volume in the first second
(FEV1) - The maximal volume of air expelled
during the first second of the FVC maneuver.
FEV1/FVC - The ratio of FEV1
to FVC, which in healthy subjects is generally 75-80%.
Forced Expiratory Flow (FEF) - The flow of air
expelled from the lungs at specific intervals during the FVC
maneuver. FEF25-75% represents the flow of air from the
small airways and is measured during the middle portion of the
Residual Volume (RV) - The volume of air that
remains in the lungs after maximal exhalation.
Total Lung Capacity (TLC) - The total amount of air
in the lungs at maximal inspiration or the sum of all lung volumes
(IRV + Vt + ERV + RV)
Flow-Volume Loop - A graphic illustration of the
patients' spirometric effort. Flow is plotted against volume to
display a continuous loop from inspiration to expiration. The
overall shape of the graphic loop plays an important role in the
interpretation of pulmonary function.
Obstructive lung disease - A disease characterized
by a decrease in exhaled air flow, caused by a narrowing or
blocking of the airway.
Restrictive lung disease - A disease characterized
by a decrease in the total volume of air in a patient's lungs,
often due to a decrease in elasticity of the lung tissue or by
limited expansion of the chest wall during inhalation (chest
wall/thoracic/spinal deformity, neuromuscular weakness).