Exhaled Breathing Condensate (EBC) Features and Lung Function Decline in Chinese Adults

Inclusion criteria

1. age from 40 to 75 year olds; gender is not limited.
2. Stable COPD
3. Sign the informed consent with willingness of obeying the protocol. Exclusion criteria

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1. with known other chronic respiratory diseases except COPD (such as asthma, tuberculosis, bronchiectasis, interstitial lung disease, occupational lung diseases, sarcoidosis, lung cancer, et al);
2. had been accepted lung lobectomy or transplantation;
3. be ill with severe, or uncontrolled systemic diseases other than COPD (such as psychiatry diseases, chronic liver diseases, heart failure, auto-immunity diseases, chronic renal diseases, et al );
4. Alcoholism, drug or solvents addition;
5. Acute exacerbation COPD patients (AECOPD)

2. Control group:

Inclusion criteria According to age (+ / - 5 years), gender and smoking, to match healthy volunteers as the control group.

1. age from 40 to 75 year olds; gender is not limited.
2. FEV1 /forced vital capacity (FVC)> 70% after inhaling bronchodilators;
3. Sign the informed consent with willingness of obeying the protocol. Exclusion criteria

a. with known other chronic respiratory diseases except COPD (such as asthma, tuberculosis, bronchiectasis, interstitial lung disease, occupational lung diseases, sarcoidosis, lung cancer, et al); b. had been accepted lung lobectomy or transplantation; c. be ill with severe, or uncontrolled systemic diseases other than COPD (such as psychiatry diseases, chronic liver diseases, heart failure, auto-immunity diseases, chronic renal diseases, et al ); d. Alcoholism, drug or solvents addition; e. Acute respiratory infection in 4 weeks (rhinitis, pharyngitis, acute tracheobronchitis, pneumonia, etc.)

2.SECOND STEP: nested case-control study Inclusion criteria

1. age from 40 to 75 year olds; gender is not limited.
2. have been living in the community for more than 1 years and no plan to move in the near 3 years
3. FEV1 / FVC > 70% after inhaling bronchodilators;
4. Sign the informed consent with willingness of obeying the protocol.

Exclusion criteria

1. with known other chronic respiratory diseases except COPD (such as asthma, tuberculosis, bronchiectasis, interstitial lung disease, occupational lung diseases, sarcoidosis, lung cancer, et al);
2. had been accepted lung lobectomy or transplantation;
3. be ill with severe, or uncontrolled systemic diseases other than COPD (such as psychiatry diseases, chronic liver diseases, heart failure, auto-immunity diseases, chronic renal diseases, et al );
4. Alcoholism, drug or solvents addition;