This randomized crossover study evaluates the effects of left paratracheal pressure, cricoid pressure, and no pressure on glottic visualization during videolaryngoscopy in adult surgical patients. The primary endpoint is the Percentage of Glottic Opening (POGO) score assessed by blinded video review. Secondary endpoints include anatomical measures (glottic surface area, vertical and horizontal displacement of the glottic plane) and clinical outcomes (first-pass success, first-pass success without desaturation <90%, intubation time, Intubation Difficulty Scale, hypoxemia, hemodynamic events, airway trauma, and postoperative sore throat or dysphonia). All outcomes are collected from routine anesthetic practice and video analysis, with no additional procedures.

This randomized crossover trial will compare three laryngoscopy conditions (no pressure, cricoid pressure, left paratracheal pressure) in adult surgical patients requiring general anesthesia with tracheal intubation. Each patient undergoes all three conditions in random order, with the intubation performed using the maneuver chosen by the operator. Anatomical outcomes (POGO, glottic surface area, vertical and horizontal displacement of the glottic plane) will be assessed from video recordings by blinded evaluators. Clinical outcomes (first-pass success, composite success without desaturation <90%, intubation time, IDS, hypoxemia, hemodynamic changes, airway trauma, sore throat, dysphonia) will be collected from routine anesthetic records and PACU assessments.

Statistical Analysis Plan:

POGO: mixed-effects repeated measures model with patient as random effect, maneuver as fixed effect, adjusted for operator, BMI, and Mallampati.

Anatomical outcomes: analyzed similarly with mixed models and planned contrasts (LPP vs CP).

Clinical outcomes: analyzed as-treated, using logistic or linear regression with adjustments for baseline factors and operator as random effect.

Mediation analysis will evaluate whether improvements in POGO explain clinical benefits (first-pass success, intubation time).

Significance level set at α=0.05 (two-sided), with exploratory outcomes interpreted without multiplicity correction.

Missing data (e.g., unusable videos, missing sore throat scores) will be reported; complete-case analysis will be primary, sensitivity analysis considered if >5% missing.

Inclusion Criteria:

• Age ≥ 18 years
• Scheduled for elective surgery under general anesthesia requiring endotracheal intubation
• ASA physical status I or II
• Normal airway anatomy as assessed by the anesthesiologist (Mallampati I-II, no known or anticipated difficult airway)
• Written informed consent obtained prior to inclusion

Exclusion Criteria:

• History of difficult intubation or anticipated difficult airway
• Known upper airway anatomical abnormalities (e.g., tumors, tracheal deviation, cervical spine instability)
• BMI > 35 kg/m²
• Gastroesophageal reflux disease or increased aspiration risk
• Pregnancy
• Emergency surgery
• Allergy or contraindication to any anesthetic drugs used
• Inability to provide informed consent

What: de-identified outcome data (clinical and imaging) and analysis code; selected de-identified video frames. When: after publication. How: upon reasonable request to the sponsor/PI with data-use agreement.