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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:

1. The maneuver is performed rather slowly

The vital capacity is assessed during an inspiratory maneuver. Starting from end-tidal volume the subject expires maximally and subsequently makes a full inspiration. This is the inspiratory vital capacity (IVC). The vital capacity is assessed during an expiratory maneuver. Starting from end-tidal volume the subjects makes a full inspiration and subsequently exhales maximally. This represents the expiratory vital capacity (EVC), or ‘slow vital capacity’ in the Anglo-American literature. 2. The maneuver is performed with maximal force If the subject first fills the lung to the fullest (i.e. to total lung capacity), and then exhales forcefully and completely to residual volume, the volume change of the lung is the forced vital capacity (FVC); it would be more correct to speak of forced expiratory vital capacity (FEVC). If the subject first exhales fully to residual volume, and then inhales forcefully and fully to total lung capacity, the volume change of the lung is the forced inspiratory vital capacity (FIVC).

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.

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

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