What is the typical spirometry finding for restrictive lung disease in terms of FEV1/FVC ratio?

• A. Less than 70%
• B. Greater than 90%
• C. Normal variability
• D. Less than predicted values

Answer: (B)

In restrictive lung disease, the spirometry findings typically show a preserved or elevated FEV1/FVC ratio. This occurs because both the forced vital capacity (FVC) and the forced expiratory volume in 1 second (FEV1) are reduced proportionately. However, since the FEV1 and FVC decrease at similar rates, the ratio remains relatively normal or even greater than 70%. Specifically, it can often be greater than 90%, which is indicative of the restrictive process where the lung volumes are reduced due to stiffness in the lung tissue or complications related to the pleura or chest wall.

This is distinct from obstructive lung disease, where the FEV1 is disproportionately reduced compared to the FVC, leading to a low FEV1/FVC ratio. Hence, a finding greater than 90% confirms the presence of a restrictive pattern in spirometry results, aligning with the characteristics of restrictive lung diseases.