Exactly how is Forced expiratory volume after one second measured?!
Question:
Exactly how is Forced expiratory volume after one second measured?
Answers:
The FEV1 is the volume exhaled during the first second of a forced expiratory maneuver started from the level of total lung capacity.
report the largest value of three technically satisfactory maneuvers.
the start of the forced expiration is obtained by linear extrapolation of the steepest part of the volume-time diagram.
the extrapolated volume should not be more than 5% of the FVC or 150 mL, whichever is greater.
the FEV1 reported should not differ by more than 150 mL from the next largest FEV1, or 100 mL if the FVC is 1.0 L or less (procedures, ref. 3) If the difference is larger up to 8 maneuvers (ref. 1) should be performed.
if more than 8 maneuvers would be required to satisfy the criteria, then report the largest FEV1 with a note that reproducible measurements could not be obtained.
FEV1 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. In adults, but not in children and adolescent, FEV1%VC declines with age and height.