Airway-related complications are among the leading causes of anesthesia-associated morbidity and mortality. Therefore, the ability to predict difficult mask ventilation, laryngoscopy, and intubation before induction is essential to ensure proper preparation in patients at risk and avoid unnecessary airway manipulations in low-risk individuals. While numerous studies have focused on predicting difficult intubation, most have limited sample sizes and do not consider postoperative critical respiratory events.

In this prospective observational clinical study, we aim to investigate the relationship between commonly used preoperative airway assessment tools-including anthropometric measurements, Mallampati score, and the STOP-Bang questionnaire for obstructive sleep apnea-and the incidence of difficult mask ventilation, difficult laryngoscopy (Cormack-Lehane grading), difficult intubation, and critical respiratory events in the postoperative period.

The study will include adult patients (≥18 years) classified as ASA I-IV undergoing surgery under general anesthesia with endotracheal intubation. Data will be collected preoperatively, intraoperatively, and in the post-anesthesia care unit (PACU) by experienced anesthesia personnel. Postoperative critical respiratory events are defined as unexpected hypoxemia, hypoventilation, reintubation, or interventions required for upper/lower airway obstruction.

Difficult airway management remains one of the most significant challenges in clinical anesthesia, often leading to severe complications such as hypoxemia, aspiration, and even cardiac arrest. Despite various clinical predictors, no single assessment method reliably identifies all patients at risk. This prospective, observational study aims to comprehensively evaluate the association between preoperative airway assessment parameters and both intraoperative airway difficulty and postoperative critical respiratory events.

The preoperative assessment will include demographic characteristics, comorbidities, ASA classification, Mallampati score, and detailed anthropometric airway measurements (neck circumference, thyromental distance, sternomental distance, interincisor gap, head dimensions, presence of beard/dentition, and neck mobility). Additionally, the STOP-Bang questionnaire will be administered to assess the risk of obstructive sleep apnea (OSA).

During induction and airway management, mask ventilation difficulty will be graded, Cormack-Lehane score during laryngoscopy will be recorded, and intubation will be evaluated in terms of the number of attempts and need for adjunctive devices (stylet, bougie, fiberoptic bronchoscope, videolaryngoscope, etc.).

In the postoperative phase, patients will be monitored for critical respiratory events including unexpected hypoxemia (SpO₂ <90%), hypoventilation (RR <8/min or PaCO₂ >50 mmHg), reintubation, and any interventions (e.g., airway support, bronchodilators, cold mist, etc.) required for upper or lower airway obstruction.

The outcomes of this study may help refine preoperative screening protocols and contribute to the development of risk-based airway management strategies aimed at improving patient safety.

Inclusion Criteria:

• Age ≥ 18 years,
• ASA Physical Status I, II, III or IV,
• Undergoing elective surgery under general anesthesia with endotracheal intubation,
• Written informed consent provided

Exclusion Criteria:

• History of head and neck surgery or trauma causing anatomical deformity,
• Known congenital or acquired airway abnormality,
• Cervical spine surgery or instability,
• Age < 18 years

Adult patients undergoing elective surgical procedures requiring endotracheal intubation under general anesthesia at a tertiary hospital.