How do obstructive and restrictive patterns differ on spirometry?

• A. Obstructive: reduced FEV1 and reduced FEV1/FVC; Restrictive: reduced FVC with normal or elevated FEV1/FVC
• B. Obstructive: reduced FVC; Restrictive: reduced FEV1
• C. Obstructive and Restrictive both show reduced FEV1/FVC
• D. Obstructive: increased FEV1; Restrictive: increased FVC

Answer: (A)

On spirometry, what matters is how FEV1 and FVC change relative to each other, which is summarized by the FEV1/FVC ratio. In obstructive patterns, airway resistance makes expiratory flow drop FEV1 disproportionately, so both FEV1 and the ratio fall below normal. In restrictive patterns, lung volumes are reduced but expiratory flow relative to volume stays proportional, so FVC drops while the FEV1/FVC ratio remains normal or even higher. Therefore, the best description is that obstructive disease shows reduced FEV1 and a reduced FEV1/FVC ratio, whereas restrictive disease shows reduced FVC with a normal or elevated FEV1/FVC ratio. (Note: real-life patterns can vary and total lung capacity helps confirm restriction.)