Chronic obstructive pulmonary disease (COPD) is a preventable and treatable disease characterized by airflow limitation. Airflow limitation is not fully reversible, progresses progressively, and is associated with an abnormal inflammatory response of the lungs to harmful gases such as cigarette smoke or harmful particles. COPD primarily involves the lungs, but can also cause systemic (or extrapulmonary) adverse effects. However, some of them are reversible. There is an acute exacerbation phase and a stable phase. COPD is graded according to the decline in FEV1. Grading criteria Recommended treatment measures Grade I: Mild ≥80% of expected value Add short-acting bronchodilators as needed Grade II: Moderate ≤FEV1<80% of expected value Add: Regular use of one or more long-acting bronchodilators Grade III: Severe ≤FEV1<50% of expected value Add: Regular use Grade IV: Very severe Expected value or FEV1<50% of expected value, with chronic respiratory failure Add: According to Long-term home oxygen therapy according to arterial oxygen status; consider surgical treatment