Which pattern is characteristic of restrictive lung disease on pulmonary function tests?

Which pattern is characteristic of restrictive lung disease on pulmonary function tests?

• A. Decreased TLC with normal or increased FEV1/FVC
• B. Increased TLC with decreased FEV1/FVC
• C. Decreased FEV1 with decreased FVC and decreased ratio
• D. Normal TLC with decreased FEV1/FVC

Answer: (A)

Restrictive lung disease limits how much the lungs can expand, so the total lung capacity (TLC) is reduced. On pulmonary function tests, this shows up as a lower TLC, and FVC tends to decrease as well. However, FEV1 and FVC drop in parallel enough that the FEV1/FVC ratio stays normal or can be increased. That combination—decreased TLC with a normal or increased FEV1/FVC—is the hallmark pattern of restriction. In contrast, a pattern with increased TLC and a reduced FEV1/FVC suggests obstruction with hyperinflation; a decreased FEV1 with both FEV1 and FVC falling and a reduced ratio points to obstructive disease; and a normal TLC with decreased FEV1/FVC also fits obstruction rather than restriction.

Restrictive lung disease limits how much the lungs can expand, so the total lung capacity (TLC) is reduced. On pulmonary function tests, this shows up as a lower TLC, and FVC tends to decrease as well. However, FEV1 and FVC drop in parallel enough that the FEV1/FVC ratio stays normal or can be increased. That combination—decreased TLC with a normal or increased FEV1/FVC—is the hallmark pattern of restriction.

In contrast, a pattern with increased TLC and a reduced FEV1/FVC suggests obstruction with hyperinflation; a decreased FEV1 with both FEV1 and FVC falling and a reduced ratio points to obstructive disease; and a normal TLC with decreased FEV1/FVC also fits obstruction rather than restriction.