Bronchiectasis is a clinical syndrome characterised by chronic cough, profuse sputum and/or intermittent haemoptysis, with or without shortness of breath and respiratory failure of varying severity, and abnormal thickening and dilatation of the bronchial walls as seen on lung imaging. Nebulised inhalation of N-acetylcysteine has been shown to significantly improve symptoms, shorten the length of hospital stay, reduce the rate of re-hospitalisation within six months, and improve lung function in patients with bronchiectasis with a high degree of safety. There have been no studies on the efficacy and safety of bronchoscopic irrigation with N-acetylcysteine solution in the treatment of bronchiectasis. The aim of this study was to investigate whether bronchoscopic acetylcysteine lavage combined with conventional treatment is more beneficial to patients with bronchiectasis than conventional treatment combined with conventional bronchoalveolar lavage and conventional treatment without bronchoscopy, respectively.

All patients enrolled were patients with acute exacerbation of bronchiectasis. A total of 180 patients (1:1:1 allocation) with acute exacerbation of bronchiectasis were to be enrolled. The patients were divided into control group A (conventional clinical treatment including anti-infective and expectorant therapy), control group B (bronchoalveolar lavage with saline on the basis of conventional clinical treatment, with a volume of 90 ml per target lung lobe, up to a maximum of 2 lobes, and a total volume of up to 180 ml), and experimental group C (bronchoalveolar lavage with acetylcysteine solution in combination with saline on the basis of conventional clinical treatment, with a volume of 90 ml per target lung lobe, up to a maximum of 2 lobes, and a total volume of up to 180 ml).

Inclusion Criteria:

1. Age ≥18 years and ≤80 years;
2. Chest CT suggestive of bronchiectasis;
3. meet the criteria for an acute exacerbation of bronchiectasis with symptoms such as cough, sputum, chest tightness or wheezing, and c. Patients who meet the criteria for an acute exacerbation of bronchiectasis with symptoms of cough, sputum, chest tightness or wheezing and who consent to bronchoscopy with bronchoalveolar lavage
4. patients who agreed to participate in the study and signed an informed consent form;

Exclusion Criteria:

1. Severe cardiopulmonary diseases, coagulation disorders, poor tolerance to anaesthesia, psychiatric disorders or severe neuroses that are contraindications to bronchoscopy;
2. Intraoperative findings of decreased SPO2 or inability to tolerate bronchoscopy or inability to tolerate further bronchoalveolar lavage;
3. Inability to co-operate with the study for any reason or in the opinion of the investigator, inappropriate for inclusion in the study for other reasons;
4. Bronchoscopy of patients with significant intra-airway haemorrhage who may be at risk of exacerbation due to bronchoalveolar lavage;
5. Patients with acetylcysteine allergy;
6. Missing information;

Subjects were blinded. Study personnel responsible for assessing patients' symptom scores and recording information on acute exacerbations were blinded whenever possible. The bronchoscopy operator responsible for giving bronchoalveolar lavage treatment and the person in charge of the patient's bed were not blinded. To avoid subjective bias on the part of the assessor, non-blind people should not disclose blinded information to the assessor.