Forced expiratory volume in one second

FEV1 is the volume of air expelled in the first second of maximal forced expiration from a position of full inspiration.

In normal subjects the fraction of the FVC which can be expelled in one second is:

• >80 % predicted value

FEV1:

• is reduced in obstructive respiratory disease e.g. asthma, mild to moderate chronic obstructive pulmonary disease (COPD)
• is reduced in restrictive respiratory disease e.g. pulmonary fibrosis
• correlates with maximal exercise capacity

Reference:

1. The Practitioner 2005; 249:180-188.