The measurement of markers in the expired breath condensate has proven to be a useful method for assessing and monitoring airway inflammation. The aim of this study is to determine the amounts of pH in the expired breath condensate of patients with bronchiectasis, and the relationship between pH and the severity of bronchiectasis.

The aim of this study is to determine the amounts of pH in the expired breath condensate of patients with bronchiectasis, and the relationship between pH and the severity of bronchiectasis. Further clarify the link between EBC pH and the risk of future acute exacerbations, mortality and lung function decline through a one-year follow-up. Hoping to explore new validated biomarkers of the disease severity and progression in bronchiectasis. During the observation, EBC pH and other valid indicators will be measured when patients were enrolled.

Inclusion Criteria:Each subject must meet all of the following criteria to be included in this study:

1. Willing to join in and sign the informed consent form.
2. Age>18 years, the diagnosis of bronchiectasis need reference to the definition of "non-cystic fibrosis bronchiectasis guideline" published by British Thoracic Society in 2010 or 2012 China bronchiectasis expert consensus, clinical symptoms of cough and expectoration, with or without intermittent hemoptysis, and chest CT showed bronchiectasis there.
3. All patients were clinically stable and had no evidence of infection or acute infective exacerbation (lower or upper respiratory tract) for at least 4 weeks before the study.
4. Patients with good compliance: the subject must be willing to follow the test plan requirements in the research center to complete all the assessment of the visit.

Control Subjects:

1. All normal subjects had a negative history of allergy (negative skin prick tests to common allergens);
2. Normal lung function, and normal bronchial reactivity.
3. No history of any lung disease (except for the history of pneumonia in the past time and small pulmonary nodules).

Exclusion Criteria:Subjects who meet any of the following criteria should be excluded from this study:

1. Patients with a history of other respiratory diseases (cystic fibrosis, allergic bronchopulmonary aspergillosis, asthma, 1-antitrypsin deficiency, pulmonary tuberculosis, COPD, lung cancer, interstitial lung disease)and atopic diseases were excluded；
2. Serious comorbidities (chronic renal failure, hepatic disease, etc.) ;
3. Patients were on inhaled or oral mucolytics, or were receiving oxygen therapy or long-term oral antibiotics；
4. Poor compliance or cannot cooperate judged by doctors;
5. Participated in other clinical trials for nearly three months;

The age of all subjects are older than 18 . The diagnosis of bronchiectasis need reference to the guideline published by BTS in 2010 or 2012 China bronchiectasis expert consensus, clinical symptoms of cough and expectoration, with or without intermittent hemoptysis, and chest CT showed bronchiectasis there.All patients were clinically stable and had no evidence of exacerbation for at least 4 weeks before the study and had a negative history of allergy. None of patients had reversibility with inhaled salbutamol of 12% or more of predicted FEV1; All normal subjects had a negative history of allergy and normal lung function, they have no history of any lung disease (except for the history of pneumonia in the past time and small pulmonary nodules).