Early chronic obstructive pulmonary disease: Beyond spirometry

Figure 2 Lung function decline in chronic obstructive pulmonary disease. Forced expiratory volume in 1 second (FEV₁) declines at a rate of about 40 mL/year when FEV₁ is 80% or more; in some at risk populations such as those with AATD it may be much higher. When FEV₁ is between 50%-80% FEV₁ declines fastest, ranging 50-80 mL/year, then declines to a rate of 35 mL/year or less once FEV₁ reaches 30% predicted.