Which finding is characteristic of restrictive lung disease?

• A. Decreased total lung capacity with a normal FEV1/FVC ratio
• B. Increased FEV1/FVC ratio with increased FVC
• C. Decreased FEV1/FVC ratio with normal TLC
• D. Normal lung volumes with decreased DLCO

Answer: (A)

Restrictive lung disease lowers the amount the lungs can hold, so total lung capacity is reduced. Because the limitation affects the lung’s volume rather than airflow during exhalation, FEV1 and FVC fall together in parallel, so the FEV1/FVC ratio stays normal or may even be higher. This pattern—decreased total lung capacity with a normal (or increased) FEV1/FVC ratio—is the classic clue of restriction.

The other patterns don’t fit as well: a scenario with an increased FEV1/FVC ratio and increased FVC isn’t typical of restriction and suggests an unusual or mixed pattern; a decreased FEV1/FVC ratio with normal TLC points more to obstructive disease; normal lung volumes with decreased DLCO suggests a diffusion problem without necessarily reduced volumes.