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Spirometry Definitions

The below is a list of all the definitions / acronyms used for evaluating spirometry results.


Forced Expiratory Volume in 1 Second. FEV1 is the amount of air which can be exhaled from the lungs in 1 second


Forced Vital Capacity. FVC is the total amount of air which can be exhaled from the lungs forcibly.

FEV1/FVC Ratio

FEV1/FVC ratio is a useful index of airflow limitation or obstruction. In the healthy lung 75- 85% of FVC is expired in one second.


Forced Expiratory Time. Time required to perform the FVC manoeuvre. In normal healthy adults it usually takes about 6 seconds but can take up to 15 seconds in patients suffering from obstructive diseases such as COPD.


Forced Expiratory Volume in 6 seconds. Maximum volume of air that can be expired with maximally forced effort in 6 seconds.


Peak Expiratory Flow. Largest expiratory flow achieved during the forced expiratory manoeuvre initiated at full inspiration.

Flows within the small airways

  • FEF25–75% – forced expiratory flow between 25% and 75% of FVC
  • FEF50% – forced expiratory flow at 50% of FVC
  • FEF75% – forced expiratory flow at 75% of FVC
Updated on March 2, 2021

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