Predictors of the need for airway adjuncts during mask ventilation in Thai adult patients undergoing general anesthesia: A prospective observational study

Background Mask ventilation is a cornerstone of airway management during general anesthesia, yet the need for airway adjuncts during mask ventilation remains poorly predicted by current preoperative assessments. We aimed to identify independent clinical predictors of this outcome in Thai adults undergoing elective surgery. Methods This single-center prospective observational study included 266 adults undergoing elective general anesthesia at a university hospital in Thailand between September 2018 and October 2019. Preoperative airway assessment included Mallampati classification, dentition status, neck circumference, history of snoring or obstructive sleep apnea (OSA), and other standard variables. The primary outcome was the need for airway adjuncts or optimization during mask ventilation, defined as Han grade ≥2. Han grade ≥2 was selected because only 10 grade-3 events occurred, yielding an events-per-variable ratio of 2.5 under the grade ≥3 definition — insufficient for reliable multivariable regression. Independent predictors were identified using multivariable logistic regression with backward stepwise elimination. Discriminative ability was evaluated using receiver operating characteristic (ROC) analysis and area under the curve (AUC) for both neck circumference alone and the complete four-variable model. Bootstrap internal validation (1,000 resamples) was performed by repeating the model-building procedure, including univariable screening and backward stepwise elimination, within each resample. Results The need for airway adjuncts (Han grade ≥2) occurred in 48 patients (18.0%); 38 (14.3%) had Han grade 2 and 10 (3.8%) had Han grade 3. Four variables were independently associated with the need for airway adjuncts in the multivariable logistic regression analysis: snoring or OSA (aOR 5.27, 95% CI 1.94–14.35), absence of ≥2 upper incisors (aOR 2.30, 95% CI 1.08–4.89), neck circumference ≥35 cm (aOR 3.02, 95% CI 1.42–6.44), and Mallampati class III–IV (aOR 2.47, 95% CI 1.22–4.97). The final four-variable model had an apparent AUC of 0.804 (95% CI 0.745–0.862). Bootstrap internal validation with 1,000 resamples, repeating the model-building procedure within each resample, yielded a mean optimism of 0.040 and an optimism-corrected AUC of 0.764 (95% bootstrap interval 0.708–0.820). The Hosmer–Lemeshow goodness-of-fit test showed no evidence of poor model fit (P = 0.077). A simple bedside integer risk score (0–5 points) had an AUC of 0.801. At an exploratory cutoff of ≥3, the sensitivity was 0.85, specificity 0.63, PPV 0.34, and NPV 0.95. Conclusion Snoring or OSA, neck circumference ≥35 cm, Mallampati class III–IV, and absence of ≥2 upper incisors were independently associated with the need for airway adjuncts during mask ventilation in Thai adult patients. All four predictors can be assessed at the bedside without additional equipment, suggesting their integration into routine preoperative airway evaluation. As a single-center derivation study, these findings are hypothesis-generating and require external validation in independent Southeast Asian cohorts before clinical adoption.