What do pulmonary function tests (PFTs) typically reveal in restrictive pulmonary disease?

In restrictive pulmonary disease, pulmonary function tests (PFTs) typically demonstrate an increase in the FEV1/FVC ratio alongside a decrease in total lung capacity (TLC). This occurs because both the forced expiratory volume in 1 second (FEV1) and the forced vital capacity (FVC) decrease, but the FEV1 does not decrease as much as the FVC, resulting in a relatively preserved or increased FEV1/FVC ratio.

Restrictive lung diseases, such as pulmonary fibrosis and sarcoidosis, limit lung expansion, leading to decreased volumes in total lung capacity. While FEV1 and FVC are both reduced, the ratio can remain normal or slightly increase. This contrasts with obstructive lung diseases, where the FEV1 is disproportionately reduced relative to FVC, leading to a decreased FEV1/FVC ratio. Thus, the findings of increased FEV1/FVC and decreased TLC clearly align with the physiological changes seen in restrictive pulmonary disease.