Emphysema is a pathological change, not a respiratory disease, so there is no such thing as acute or chronic. The term here should be chronic obstructive pulmonary disease. Chronic obstructive pulmonary disease, referred to as COPD, is a common, preventable and treatable disease characterized by persistent respiratory symptoms and airflow limitation, usually associated with airway and/or alveolar abnormalities caused by significant exposure to harmful particles or gases. Pulmonary function tests are important in determining airflow limitation, and a ratio of first-second force expiratory volume (FEV₁) to forceful lung volume (FVC) (FEV₁/FVC) <70% after inhalation of bronchodilators indicates persistent airflow limitation. COPD is closely related to chronic bronchitis and emphysema. If COPD is diagnosed, early and standardized treatment is recommended to minimize the adverse effects of the disease.