Pulmonary Testing Basic Terminology for PFT's

Forced Vital Capacity (FVC) - The volume of air expelled by a forced maximal expiration from a position of maximal inspiration.

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 FVC.

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).

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