Clinical Study on the Efficacy of Subglottic Suction in Mechanically Ventilated Patients Guided by Bedside Ultrasound

Inclusion Criteria: * 1\. Patients admitted to the ICU with the patient or their legal representative having signed an informed consent form; 2. Patients expected to have an oral artificial airway in place for ≥72 hours; 3. Patients using tracheostomy tubes with subglottic suctioning Exclusion Criteria: * 1\) Severe cervical deformity, extensive subcutaneous emphysema, thick dressing coverage, or severe obesity that prevents clear visualization of the subglottic region by ultrasound. 2\) Coagulopathy (platelets \<50×10⁹/L) or active bleeding tendency, which may induce airway bleeding due to suctioning procedures. 3\) Presence of organic airway disease or previous cervical surgery history, affecting assessment of the subglottic region. 4\) Tracheostomy patients. 5) Patients allergic to ultrasound coupling agents, or those unable to cooperate with cervical ultrasound examination due to severe agitation. 6\) Patients with existing pulmonary infection upon admission. 7) Patients intubated for treatment of known aspiration. 8) History of lung cancer or head and neck cancer that may produce alpha-amylase in the lungs. 9\) History of conditions affecting salivary secretion (e.g., Sjögren's syndrome).