Long-term change in reactance by forced oscillation technique correlates with FEV1 decline in moderate COPD patients

Since the landmark study of the natural history of chronic obstructive pulmonary disease (COPD) by Fletcher and Peto [1], lung function decline has been an issue of great concern and an important therapeutic target. The annual decline in forced expiratory volume in 1 s (FEV1) is generally used as a marker of disease progression. A review of large longitudinal studies found that the mean rate of FEV1 decline was highest at Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage II (47–79 mL·year−1), indicating the need for treatment at earlier stages of the disease [2].