Predictors of difficult suspension laryngoscopy: A prospective study based on objective anthropometric measurements

The aim of this study was to investigate the predictive value of preoperatively measurable anthropometric parameters for difficult suspension laryngoscopy (DSL) and to determine objective cut-off values that may be used in clinical practice.

Between April 1, 2024, and September 1, 2024, a total of 70 patients undergoing suspension laryngoscopy were prospectively evaluated. Demographic characteristics and anthropometric measurements, including body mass index (BMI), mouth opening, hyomental, thyromental, and sternomental distances, were recorded in both neutral and extension positions. Laryngeal exposure was graded according to the classification proposed by Roh et al. Patients with Grade 1-2 exposure were classified as the easy suspension laryngoscopy (ESL) group, whereas those with Grade 3-4 exposure were classified as the difficult suspension laryngoscopy (DSL) group. Receiver operating characteristic (ROC) curve analysis and logistic regression were used to identify predictive factors and optimal cut-off values.

Easy suspension laryngoscopy was achieved in 42 patients (60%), while 28 patients (40%) were classified as DSL. Significant correlations were found between DSL and BMI, mouth opening, sternomental distance, and extension-based neck measurements. ROC analysis revealed the following cut-off values: BMI > 24.62 kg/m² (sensitivity 92.86%), mouth opening ≤ 47 mm (specificity 88.10%), sternomental distance measured in extension (ESMU) ≤ 155 mm, and vertical thyromental distance measured in extension ≤ 67 mm. Univariate logistic regression demonstrated a 9.75-fold increased risk of DSL for BMI > 24.62 kg/m² and a 5.55-fold increased risk for mouth opening ≤ 47 mm. In multivariate analysis, suspension force > 4.02 kg remained the only independent predictor of DSL (OR: 7.389, p < 0.001). A combined preoperative DSL Risk Score integrating all four objective parameters achieved an AUC of 0.789 - exceeding that of any individual predictor, including the intraoperative suspension force (AUC 0.774) - with a sensitivity of 78.6% and specificity of 64.3% at the optimal cut-off of ≥ 2.

Objective anthropometric parameters and their defined cut-off values are effective in predicting difficult suspension laryngoscopy. A simple, four-item additive DSL Risk Score combining BMI, mouth opening, and two neck measurements obtained in cervical extension provides superior predictive performance to any individual parameter and constitutes a clinically applicable preoperative risk stratification tool. External validation in larger and ethnically diverse cohorts is warranted.