1. Main objectives: ① To determine the optimal timing for bronchoscopic lung lavage in treating severe pneumonia in children, providing evidence-based guidance for the standardized clinical implementation of this technique. ② To establish a multidimensional efficacy evaluation system encompassing clinical symptoms, blood gas analysis, and inflammatory markers.
2. Secondary objectives: ① To assess the impact of different intervention timings on clinical outcomes, including the time to temperature normalization, resolution of lung rales, length of hospital stay, hospitalization costs, and mortality rate. ② To evaluate the therapeutic effects at the pathophysiological level by measuring inflammatory factors (e.g., IL-6, IL-8), epithelial/endothelial injury biomarkers (e.g., SP-D, angiopoietin-2), and indicators of pathogen clearance, thereby clarifying the treatment's effects on inflammation control, lung injury repair, and pathogen elimination. ③ To enhance the accumulation of safety data by calculating the incidence of adverse events related to bronchoscopic procedures (such as airway bleeding and hypoxemia) and further defining the safety profile of this technique in the pediatric population.

(1) Methods: This study is a multicenter, prospective, non-randomized concurrent control study. Participants were grouped based on whether the parents of the children consented to bronchoscopy intervention. Subjects were randomly assigned to the early group, the late group, or the standard treatment group in a 1:1:1 ratio. Random numbers were assigned to subjects according to their order of enrollment.

• Early BALF Group (EB): After the children were diagnosed with severe pediatric pneumonia, bronchoscopic bronchoalveolar lavage combined with standardized basic treatment was performed within 24 hours. Relevant indicators were collected on the first day of enrollment and on the seventh day after treatment.

• Late BALF Group (LB): After the children were diagnosed with severe pediatric pneumonia, bronchoscopic lung lavage combined with standardized basic treatment was performed within 72 hours. Relevant indicators were collected on the day of enrollment and on the seventh day after treatment.

• Standard Treatment Group (ST): Received only standardized basic treatment and did not undergo bronchoscopic lung lavage throughout the study. The same indicators were collected on the first day of enrollment and on the seventh day after treatment.

  (2) Subjects: This study aims to include children aged 1 to 14 years who are clinically diagnosed with severe pneumonia between December 2025 and December 2028. Patient sources include children with severe pneumonia admitted to general internal medicine departments or pediatric intensive care units (PICUs) at each research center.

  (3) Process:

  1. Pre-screening Before Enrollment: ①Collection of basic information; ② Verification of inclusion and exclusion criteria; ③Signing the informed consent form.
  2. Baseline Assessment: ①Age, gender, and weight; ②Onset time, pathogen type, hospitalization duration, hospitalization cost, and mortality rate; ③Form of respiratory support (mechanical ventilation, non-invasive ventilation, mask, or nasal cannula); ④Clinical symptoms and signs, including body temperature and pulmonary rales); ⑤Laboratory tests: blood gas analysis; complete blood count; C-reactive protein (CRP); procalcitonin (PCT); interleukins IL-6 and IL-8; tumor necrosis factor-alpha (TNF-α); surfactant protein D (SP-D); and angiopoietin-2; ⑥ Extent of pulmonary involvement on imaging (multilobar or single-lobe involvement); ⑦Complications of bronchial alveolar lavage.
  3. Intervention Measures: All children receive the standardized basic treatment recommended in the "Clinical Diagnosis and Treatment Guidelines for Community-Acquired Pneumonia in Children (2019 Edition). early group and the late group receive bronchial lung alveolar lavage therapy. The specific procedures are as follows:

• Standardized Basic Treatment: ①Anti-infection treatment: Based on pathogen detection results (such as sputum culture or nucleic acid testing) or clinical experience, select appropriate antibacterial drugs (e.g., cephalosporins, macrolides) or antiviral drugs (e.g., oseltamivir, acyclovir). Administer primarily via intravenous infusion, with dosage calculated according to the child's weight (mg/kg) and frequency following the drug's instructions. ②Respiratory support treatment: Provide nasal cannula high-flow oxygen therapy (flow rate 5-8 L/min), non-invasive ventilation (e.g., bilevel positive airway pressure, with pressure set at 8-12 cmH₂O), or invasive mechanical ventilation (tidal volume 6-8 mL/kg, respiratory rate adjusted according to age). ③Symptomatic supportive treatment: Administer ambroxol (intravenous infusion, 7.5-15 mg per dose, 2-3 times daily) for expectoration; gamma globulin (intravenous infusion, 400-800 mg/kg/day for 3-5 days) to regulate immunity; nebulization therapy (budesonide, ipratropium bromide, salbutamol hydrochloride); enteral or parenteral nutrition support (e.g., amino acids, fat emulsion); and maintain water and electrolyte balance (e.g., fluid replacement, correction of acid-base disorders). Continuously monitor heart rate, blood pressure, and SpO₂. If SpO₂ falls below 85% or arrhythmia occurs, immediately suspend the procedure, provide high-concentration oxygen therapy until vital signs stabilize, and then re-evaluate.

• Unified Standard for Alveolar Lavage Operation: All centers use commonly available pediatric electronic bronchoscopes (outer diameter 4.0-4.2 mm, operating channel 2.0 mm; or outer diameter 2.8-3.2 mm, operating channel 1.2 mm). The bronchoscope is inserted through the nasal or tracheal intubation route to locate the lesion in the lung segment under direct visualization. The lavage dose follows the "Guidelines for Pediatric flexible Bronchoscopy (2018 Edition)": after the bronchoscope is positioned in the target bronchus, 37°C normal saline (1 mL/kg per instillation, maximum 20 mL per instillation, total ≤ 5-10 mL/kg) is injected through the working channel. The lavage fluid is then aspirated using negative pressure of 100-200 mmHg (1 mmHg = 0.133 kPa). The selected negative pressure should be appropriate to avoid bronchial collapse during aspiration. The collected lavage fluid is sent to the laboratory for standardized testing. Throughout the procedure, continuous monitoring of heart rate, blood pressure, and SpO₂ is performed. If SpO₂ falls below 85% or arrhythmia occurs, the procedure should be immediately suspended, and high-concentration oxygen therapy administered until vital signs stabilize before re-evaluation.

  (4) Follow-Up Assessment:The period from enrollment to the collection of clinical data and laboratory indicators in this study was one week. After enrollment, the subjects were required to complete two visits: one at the end of the first week after discharge and another one month after discharge.

  • Visit 1: One week after discharge

    ① Assessment of clinical symptoms and signs, including body temperature, cough, wheezing, lung auscultation, SpO₂ monitoring, feeding, and mental state.

    • Complete Blood Count and C-Reactive Protein (CRP) Test

  • Visit 2: One month after discharge

    • Assessment of clinical symptoms and signs, including body temperature, cough, wheezing, lung auscultation, SpO₂ monitoring, feeding, and mental state; ② Complete blood count with CRP test and chest X-ray examination.

Inclusion Criteria:

1. According to the on Clinical Warning and Early Decision-making for Severe Pneumonia in Children, severe pneumonia is diagnosed when any of the following symptoms are present: poor general condition; refusal to eat or dehydration; altered consciousness; significantly increased respiratory rate (RR) (RR > 70 breaths per minute for infants or RR > 50 breaths per minute for older children); central cyanosis; respiratory distress (including groaning, nasal flaring, and use of accessory muscles indicated by three concave signs), involvement of multiple lung lobes or ≥ 2/3 of one lung; pleural effusion; pulse oxygen saturation ≤ 0.92 at sea level; or any extrapulmonary complications. The presence of any of these conditions qualifies as severe pneumonia.
2. The time from onset to enrollment was ≤ 72 hours, and the patient had not received bronchoscopic lavage treatment.

Exclusion Criteria:

1. Having severe underlying diseases: congenital heart disease, bronchopulmonary dysplasia, malignant tumors, severe immunodeficiency diseases, etc.
2. There are contraindications for performing a bronchoscopy examination.
3. Respiratory tract foreign bodies, airway developmental malformations, etc.

ll relevant data supporting the findings of this study can be accessed upon reasonable request from the Project Manager at zjuent@zju.edu.cn.