Small airways obstruction syndrome.

STUDY OBJECTIVES: To clarify the significance of a functional lung pattern characterized by a decreased vital capacity (VC) and an increased residual volume (RV), but with a normal FEV1/VC ratio. SETTING: A university teaching hospital. SUBJECTS: Patients with bronchial asthma, pulmonary emphysema, and small airways disease, and older subjects. MEASUREMENTS: Measurements of static and dynamic lung volumes, diffusing capacity of the lung for carbon monoxide (as measured by the single-breath method), nitrogen slope of the alveolar plateau, and closing volume (as measured by the single-breath O2 test). CONCLUSION: A functional pattern characterized by a decreased VC and FEV1 and increased RV, but with a normal FEV1/VC ratio and total lung capacity, reflects an obstructive impairment of small airways.