A total of 103 elective surgery patients who met the inclusion criteria were selected. After screening for eligibility according to the inclusion and exclusion criteria and signing informed consent, they were randomly divided into two groups. Upon entering the operating room, routine ECG monitoring was initiated, and a peripheral vein was opened. Ultrasound was used to measure the baseline cross-sectional area (CSA) of the gastric antrum in the supine position. After general anesthesia induction, positive pressure ventilation was applied via face mask. Group A received no external compression, while Group B underwent esophageal compression under ultrasound guidance.

Upon entering the operating room, intravenous access is established, and oxygen is administered. Standard vital sign monitoring is initiated, including heart rate, non-invasive blood pressure, peripheral oxygen saturation, temperature monitoring, and BIS monitoring. Ultrasound is used to measure the cross-sectional area (CSA) of the gastric antrum before the onset of FMV.

Oxygen is administered via face mask for denitrogenation, with 100% pure oxygen (6 L/min flow rate). Intravenous medications are sequentially administered: midazolam 0.03 mg/kg, propofol 1-2 mg/kg, sufentanil 0.5 μg/kg, remifentanil 1 μg/kg, and rocuronium bromide 0.6 mg/kg. After the patient loses consciousness and the eyelash reflex is absent, FMV is initiated. The trial employs a pressure-controlled ventilation (PCV) mode with a pressure of 18 cmH2O, a level sufficient to provide adequate alveolar ventilation while staying below the threshold for significant gastroesophageal regurgitation. The respiratory rate is set at 14 breaths per minute with an inspiration-to-expiration ratio of 1:2.

After three minutes of FMV, the gastric antrum CSA is measured again in supine, semi-recumbent, and right lateral decubitus positions. Video laryngoscopy is used to record POGO scores before and after ultrasound-guided esophageal compression, and after 4 minutes of ventilation, tracheal intubation is performed. Grouping:

Group A (Control Group): No esophageal compression is applied, and FMV is performed for 4 minutes.

Group B (Intervention Group): Ultrasound-guided esophageal compression plus FMV: before the start of FMV, ultrasound is used to locate the esophagus, and pressure is applied to the esophagus at the cricoid level to collapse the esophageal lumen. Esophageal pressure is released just before tracheal intubation following 4 minutes of ventilation.

Inclusion Criteria:

• Age 18 to 65 years
• American Society of Anesthesiologists (ASA) Physical Status Classification I-II.
• Body Mass Index (BMI) between 18 and 28 kg/m².
• Patients undergoing elective tracheal intubation for general anesthesia.
• Patients scheduled for laparoscopic surgery.
• Fasting for ≥8 hours and abstaining from liquids for ≥2 hours before surgery, with low risk of gastroesophageal regurgitation and aspiration.

Exclusion Criteria:

• Suspected difficult FMV (e.g., age >55 years, BMI >26 kg/m², edentulous, history of snoring, and long beard; presence of two or more factors).
• Pre-existing respiratory, pharyngeal, laryngeal, facial, or neck pathology.
• History of gastrointestinal surgery, gastroesophageal reflux disease (GERD), or high risk of aspiration.
• Severe cardiac, cerebral, pulmonary, hepatic, or renal diseases.
• Patients requiring non-invasive ventilation prior to surgery.
• Patients currently participating in other clinical trials or who refuse to participate.