Disease stage Main characteristics
1: Mild COPD FEV1/FVC < 70%
FEV1 ≥ 80% predicted
With or without symptoms
2: Moderate COPD FEV1/FVC < 70%
50% ≤ FEV1 < 80% predicted
With or without symptoms
3: Severe COPD FEV1/FVC < 70%
30% ≤ FEV1 < 50% predicted
With or without symptoms
4: Very severe COPD FEV1/FVC < 70%
FEV1 < 30% predicted or < 50% predicted plus presence of
chronic respiratory failure (PaO2 < 60 mm Hg while breathing
room air at sea level)
Table 1: Classification of COPD stages based on spirometry [9]. FEV1 = Forced Expiratory Volume in 1 sec; FVC = Forced Vital Capacity; PaO2 = Arterial Partial Pressure of Oxygen.
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