forced vital capacity

Last reviewed 01/2018

This is the volume of air expelled by a forced maximal expiration from a position of full inspiration. The value for FVC may be slightly less than for VC.

The FVC is:

  • usually 3-6 litres, varying with age, gender and height
  • reduced in obstructive and restrictive defects
  • correlated with disability in chronic respiratory disaese

The FVC is reduced in both obstructive and restrictive respiratory disease:

  • in patients with airways obstruction the FEV1 is disproportionately reduced as compared to the FVC, resulting in a low FEV1/FVC ratio

  • in patients with restrictive pulmonary disease the FEV1 and FVC fall proportionately, resulting in normal values for FEV1/FVC