A.Ⅳ級(jí)FEV₁／FVC<70%，F(xiàn)EV₁<30%預(yù)計(jì)值或FEV₁<50%預(yù)計(jì)值，伴有慢性呼吸衰竭
B.Ⅲ級(jí)FEV₁／FVC<70%，30%≤FEV₁≤50%預(yù)計(jì)值
C.Ⅱ級(jí)FEV₁/FVC<70%，50%≤FEV₁≤80%預(yù)計(jì)值
D.Ⅰ級(jí)FEV₁／FVC<70%，F(xiàn)EV₁>80%預(yù)計(jì)值
E.0級(jí)FEV₁／FVC<70%，有罹患COPD的危險(xiǎn)因素