Forced Expiratory Flow (FEF)

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Forced expiratory Flow measures the total flow rate during a forced vital capacity maneuver. The flow/volume curve is divided into quarters that are expressed as FEF25%, FEF50%, and FEF75% of FVC.


FEF25% - This measurement describes the amount of air that was forcibly expelled in the first 25% of the total forced vital capacity test.


FEF50% - This measurement describes the amount of air expelled from the lungs during the first half (50%) of the forced vital capacity test.


FEF25%-75% - This measurement describes the amount of air expelled from the lungs during the middle half of the forced vital capacity test.