Hydrogen Sulfide and Pulmonary Vascular Remodeling on HRCT in Patients With COPD

Inclusion Criteria: * Patients meet the GOLD 2016 guidelines for diagnostic criteria of COPD: dyspnea, chronic cough and/or sputum symptoms, exposure to risk factors, and pulmonary function after inhalation of bronchodilator with forced expiratory volume (FEV1)/forced vital capacity (FVC) \< 70%. Exclusion Criteria: \- 1. Other lung diseases such as pneumonia, lung cancer, tuberculosis, pulmonary embolism, heart diseases such as heart failure, ventricular septal defect, patent ductus arteriosus, thoracic deformity and pleural diseases. 2\. Patients who are unable to understand and/or complete questionnaire.