Forced expiratory volume in 1 second (FEV1)

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. FEV1%VC declines with age and height.
As IVC > EVC > FVC in patients with obstructive lung disease, the VC should be specified when using the FEV1/VC ratio, hence FEV1%FVC (forced expiratory ratio, FER) or FEV1%IVC. The Tiffeneau-index is FEV1%IVC (ref. 2).

Ref. 1 - If 8 maneuvers have not led to a FVC or FEV1 meeting the above requirements for reproducibility, then further attempts are useless:

1. Ferris BG Jr, Speizer FE, Bishop Y, Prang G, Weener J. Spirometry for an epidemiologic study: deriving optimum summary statistics for each subject. Bull Europ Physiopathol Respir 1978; 14: 145-166.
2. Kanner RE,Schenker MB, Munoz A, Speizer FE. Spirometry in children: methodology for obtaining optimal results for clinical and epidemiological studies. Am Rev Respir Dis 1983; 127: 720-724.

Ref. 2 - Tiffeneau index:

1. Tiffeneau R, Pinelli A. Air circulant et air captif dans l’exploration de la fonction ventilatoire pulmonaire. Paris Med 1947; 133: 624-631.>

Recommended procedures:

1. Quanjer PhH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes and forced ventilatory flows. Official Statement of the European Respiratory Society. Eur Respir J 1993; 6 suppl. 16: 5-40. Erratum Eur Respir J 1995; 8: 1629.
2. American Thoracic Society. Standardization of spirometry: 1994 update. Am J Respir Crit C>Miller MR et al. Standardisation of spirometry. ATS/ERS task force: standardisation of lung function testing. Eur Respir J 2005; 26: 319-338.