Forced Expiratory Time (FET) and Forced Expiratory Volume (FEV) are two different things.
Forced Expiratory Volume in One Second (FEV1)
The volume of air exhaled during the first second of a forced expiratory maneuver. The FEV1 is useful for detecting obstructive diseases since a person with obstructed airways will not be able to exhale as much air in the first second as a person with normal lungs. The FEV1 may also be low if the person has severe restrictive disease.
Forced Expiratory Time (FET):
The time taken to expire a given volume during measurement of forced vital capacity.
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