Practical challenges of diagnosing obstruction in the presence of restriction

The role of the pulmonary function laboratory to assist in disease management: interstitial lung disease

“…As this pattern is not always related to restriction, confirmation with measurements of lung volumes is usually required (i.e., TLC < lower limit of normal). 2 A common mistake is the assumption that a preserved FVC rules out restriction: a sizeable fraction of patients with early/mild ILD-as in the present case-shows low TLC but preserved (F)VC, provided RV decreases in tandem with TLC. 3 Not infrequently in mild disease, FVC is still preserved, but the mid-expiratory flows are supranormal, indicating increased lung elastic recoil.…”