FEV1/FVC ratio

Overview
The FEV1/FVC ratio is a calculated ratio used in the diagnosis of obstructive and restrictive lung disease.

It represents the proportion of the forced vital capacity exhaled in the first second.

Disease States
In obstructive lung disease, the FEV1 is reduced due to obstruction to air escape. Thus, the FEV1/FVC ratio will be reduced.

In restrictive lung disease, the FEV1 and FVC are equally reduced due to fibrosis or other lung pathology (not obstructive pathology). Thus, the FEV1/FVC ratio should be approximately normal.