In restrictive disease of lungs
FEV1 (forced expiratory volume in the first second)
The fraction of the VC expired during the first second of a forced expiration. ( FEV1 )
Forced vital capacity
The largest amount of air that can be expired after a maximal inspiratory effort. ( FVC ).
In normal healthy males FEV1/FVC is 80%
in restrictive disease of lungs, FVC is decreased but FEV1 is not. thus the ratio of FEV1/FVC increase.