Severity of COPD

Diagnosis criteria

Stage I: Mild airflow obstruction

FEV₁% < 70%

FEV₁ > 80% of Standard FEV₁

Stage II: Moderate airflow obstruction

FEV₁% < 70%

FEV₁ < 80% of Standard FEV₁

Stage III: Advanced airflow obstruction

FEV₁% < 70%

FEV₁ < 50% of Standard FEV₁

stage IV: Extremely advanced airflow obstruction

FEV₁% < 70%

FEV₁ < 30% of Standard FEV₁