Multicenter Study of Impulse Oscillometry in Chinese

Inclusion Criteria for healthy subjects: * life-long non-smokers * no symptoms and history of chronic cardiopulmonary diseases (chronic bronchitis, asthma, lung cancer, pulmonary fibrosis, pulmonary tuberculosis, chronic heart diseases, etc.) * no abnormal findings on physical examination * written informed consent was obtained Inclusion Criteria for COPD: * Diagnosis of chronic obstructive pulmonary disease (COPD), as classified by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines and post-bronchodilator FEV1/FVC (forced vital capacity) \< 70%. Inclusion Criteria for asthma: * Diagnosis of asthma, as classified by national and international asthma guidelines. Inclusion Criteria for ILD: * ILD diagnosis confirmed by lung biopsy, X ray or BALF analysis. Inclusion Criteria for UAO: * Diagnosis of UAO. Exclusion Criteria for healthy subjects: * upper or lower respiratory infection within 4 weeks * long-term exposure to harmful gas or particles * using β-blocker for treatment * pregnant women, epileptic * other diseases or surgeries potentially affecting lung function