[Further examination of COPD using spirometry, respiratory function test, and impulse oscillometry].

Spirometry is essential for diagnosis and staging of chronic obstructive pulmonary disease (COPD). Characteristic of physiological change of small airways in COPD is heterogeneous distribution of small airway narrowing, resulting in air-trapping and nonhomogeneous ventilation. FEF25-75, residual volume/total lung capacity, delta N2 in phase III slope of single breath N2 washout test, closing volume, static and dynamic compliance, and carbon monoxide diffusing capacity (transfer factor) are measured for detecting small airways disease. Impulse oscillometry is also useful for assessment of small airways disease, especially indices of frequent resonance (Fres) and frequent dependent of resistance change of R5-R20; resistance at 5 Hz minus resistance at 20 Hz. Impulse oscillometry seems to have a complemental role of spirometry in managing COPD.