VC, IVC, EVC, FVC, FIVC

VC - vital capacity

Vital capacity (VC): the volume change of the lung between a full inspiration and a maximal expiration. The maneuver may be performed in different ways:

In healthy subjects the vital capacities measured according to these different procedures are nearly the same. In patient with obstructive lung disease, however, the vital capacity obtained during expiratory maneuvers is smaller than when obtained upon inspiration:

IVC > EVC > FVC.

You should therefore always note which VC has been assessed.

IVC - inspiratory vital capacity

The volume change of the lung between a maximal expiration to residual volume and a full inspiration to total lung capacity. The inspiratory vital capacity is assessed during an inspiratory maneuver, which is not performed forcefully.

The largest of 3 technically satisfactory maneuvers, which differ by no more than 5% or 150 mL (the larger of the two) from the next largest IVC, should be reported. If the difference is larger, then perform up to 8 measurements; if the repeatability criterion is still not met then report the largest IVC with a note that reproducible measurements could not be obtained.

EVC - expiratory vital capacity / SVC - slow vital capacity

The volume change of the lung between a full inspiration to total lung capacity and a maximal expiration to residual volume.

The expiratory vital capacity is assessed during an expiratory maneuver, which is not performed forcefully. This index is called the ‘slow vital capacity’ in Anglo-American literature. The selection criteria are the same as for the IVC.

FVC - forced expiratory vital capacity

The volume change of the lung between a full inspiration to total lung capacity and a maximal expiration to residual volume. The measurement is performed during forceful exhalation; the preceding maximal inhalation need not be performed forcefully. The volume assessed is the forced expiratory vital capacity (FEVC), commonly called forced vital capacity (FVC). The maneuver is almost invariably performed in conjunction with the assessment of the FEV1 and of maximum expiratory flow-volume curves. In patients with obstructive lung disease FVC < EVC < IVC.

• report the largest value of three technically satisfactory maneuvers.
• the FVC reported should not differ by more than 150 mL from the next largest FVC, 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 are required to satisfy the criteria, then report the largest FVC with a note that reproducible measurements could not be obtained.

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.

FIVC - forced inspiratory vital capacity

The volume change of the lung between a maximal expiration to residual volume and a full inspiration to total lung capacity. The measurement is performed during forceful inhalation; the preceding maximal exhalation need not be performed forcefully. The volume assessed is the forced inspiratory vital capacity (FIVC).

At the present time forceful exhalations and inspirations are often performed in immediate succession, so that maximal expiratory and inspiratory flow-volume curves can be recorded. It matters in which order the maneuvers are performed. In a patient with pronounced airway obstruction an FIVC performed after an FVC maneuver almost invariably leads to the FIVC being larger than the FVC. If the order is reversed the FIVC and FVC are about the same: the FIVC assessed immediately after an FVC maneuver should therefore not go on record as an IVC.

• Most people find the inspiratory maneuver difficult to perform. The figure illustrates a few tidal breaths, the maximal exhalation, and then the FIVC maneuver recorded at faster paper speed.
• The measurement of the FIVC is almost invariably combined with that of the FIV1 (the volume that can be forcefully inhaled in one second starting from residual volume).
• By far the most common cause for a reduction in the FIVC is expiratory airway obstruction, occasionally restrictive lung disease.

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. Miller MR et al. Standardisation of spirometry. ATS/ERS task force: standardisation of lung function testing. Eur Respir J 2005; 26: 319-338. Erratum Eur Respir J 1995; 8: 1629.
3. Miller MR et al. Standardisation of spirometry. ATS/ERS task force: standardisation of lung function testing. Eur Respir J 2005; 26: 319-338.