The Clinical Application Value of "Showering Cells" in the Diagnosis of Aspiration Pneumonia

Inclusion Criteria: * Aged 18 to 100 years, inclusive. No absolute contraindications to bronchoscopy and consent to undergo flexible bronchoscopy. Hospitalized patients who either meet the diagnostic criteria for aspiration pneumonia or have aspiration pneumonia definitively ruled out. AP Group： 1. Imaging Findings:Newly developed dependent infiltrates on chest CT (gravity-dependent distribution of new lung infiltrates). Specifically, in the standing/sitting position, infiltrates are predominantly seen in the basal segments of the lower lobes, especially the right lower lobe. In the supine position, infiltrates are primarily located in the posterior segment of the right upper lobe and the dorsal segment of the right lower lobe. These may be accompanied by a small amount of pleural effusion or plate-like atelectasis. 2. Clinical History Characteristics:A clear history of aspiration or the presence of at least one high-risk factor for aspiration (e.g., impaired consciousness: sedated state, post-stroke, epileptic seizure; confirmed swallowing dysfunction; gastroesophageal reflux disease; abnormal gag reflex/diminished cough reflex; poor oral hygiene: periodontitis, inadequate denture cleaning; end-stage disease: advanced dementia, malignancy, etc.). 2.Meeting 2 or more of the following 3 clinical criteria:（1）.Temperature abnormality: Fever (core temperature \>38.0°C) or hypothermia (core temperature \<36.0°C, more common in elderly or immunocompromised patients).(2).Respiratory symptoms: New onset or worsening of cough, production of purulent sputum (may contain food particles or unusual odor), dyspnea, chest pain, or detection of food particles/gastric contents in tracheal secretions.(3).Abnormal peripheral inflammatory markers: White blood cell count \>10×10⁹/L or \<4×10⁹/L, or presence of a left shift (band neutrophil proportion \>5%). Non-AP Group: 1. Imaging: Chest CT reveals newly appeared or progressive pulmonary infiltrates, consolidation, or ground-glass opacities. 2. Clinical Criteria: Meeting 2 or more of the following 3 criteria: （1).Fever (core temperature \>38.0°C) or hypothermia (core temperature \<36.0°C, more common in elderly or immunocompromised patients). (2).Respiratory symptoms: Purulent or mucopurulent sputum, possibly with blood-streaked sputum; or new/worsening cough and sputum production; or accompanied by chest pain or dyspnea. (3).Abnormal peripheral white blood cell count: Total white blood cell count \>10×10⁹/L or \<4×10⁹/L, or presence of a left shift (band neutrophil proportion \>5%). 3.Exclusion: Does not meet the diagnostic criteria for aspiration pneumonia. Exclusion Criteria: 1. Younger than 18 years old or older than 100 years old. 2. Patients with absolute contraindications to performing bronchoscopy with bronchoalveolar lavage (BAL); 3. Patients who refuse to participate in the study.