Pulmonary function testing in restrictive lung disease typically shows which combination?

• A. Decreased DLCO
• B. Increased TLC
• C. Normal or increased FEV1/FVC, decreased TLC
• D. Decreased FEV1/FVC

Answer: (C)

In restrictive lung disease, the primary issue is reduced lung volumes, especially total lung capacity. On pulmonary function tests, this shows up as a decreased TLC, while the proportion of air exhaled in the first fraction of the breath (FEV1) relative to the total exhaled volume (FVC) is preserved or even increased, so the FEV1/FVC ratio is normal or higher. Diffusion capacity (DLCO) can be normal or reduced depending on the underlying cause (e.g., interstitial fibrosis often lowers DLCO, while chest wall or neuromuscular restriction may not). Therefore the best combination that reflects typical restrictive physiology is decreased TLC with a normal or increased FEV1/FVC.