The FEV1/FVC ratio (FEV1%), also known as the Tiffeneau-Pinelli index, is a spirometric parameter and refers to a calculated ratio which represents the proportion of a patients vital capacity that they are able to expire in the first second of forced expiration.
FEV1% is used in the diagnosis and assessment of obstructive (e.g. COPD) and restrictive lung disease. It is by far the most frequently used index for assessing airway obstruction, bronchoconstriction or bronchodilatation; FEV1 expressed as a percentage of the VC is the standard index for assessing and quantifying airflow limitation. The ratio declines with age and height.
Interpretation
Normal FEV1% values are approximately 70-80%. Predicted normal values can be calculated on graphs and various online tools are available.
They depend on age, sex, height, mass and ethnicity as well as the research study that they are based upon.
Another value derived from FEV1% is FEV1% predicted, which is defined as FEV1% of the patient divided by the average FEV1% in the population for any person of similar age, sex, and body composition.
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