Comparison of the variability of the annual rates of change in FEV₁ determined from serial measurements of the pre- versus post-bronchodilator FEV₁ over 5 years in mild to moderate COPD: results of the lung health study.

Comparison of the variability of the annual rates of change in FEV₁ determined from serial measurements of the pre- versus post-bronchodilator FEV₁ over 5 years in mild to moderate COPD: results of the lung health study.