Predictors for Difficult Laryngeal Exposure in Suspension Laryngoscopy: A Systematic Review and Meta-Analysis.

OBJECTIVES/HYPOTHESIS: Many researchers have investigated parameters that could independently predict difficult laryngeal exposure (DLE) in suspension laryngoscopy; however, inconsistent results and conclusions have been reported in previous studies. We conducted a meta-analysis of the existing literature to determine the parameters that are significant for a standardized preoperative DLE prediction system.

METHODS: The literature was retrieved systematically from PubMed, Embase, Web of Science, China national knowledge infrastructure (CNKI), and Wangfang until October 2022. In eligible studies, data were extracted and analyzed using the R language, and effective measures were odds ratios with 95% confidence intervals (CIs) for dichotomous variables and mean differences (MD) with 95% CIs for continuous variables.

RESULTS: The search yielded 1574 studies, of which eighteen involving 2263 patients were included. Pooled analysis demonstrated that patients with DLE during microsurgery are often men (OR =1.73, 95% CI = [1.16, 2.57]); older age (MD = 5.47 years, 95% CI = [2.44, 8.51]); high body mass index (BMI; MD = 1.19Kg/m2, 95% CI = [0.33, 2.05]); bullnecked (MD =2.50cm, 95% CI = [1.56, 3.44]); limited mouth opening (MD = -0.52cm, 95% CI = [-0.88, -0.15]); limited neck flexibility (MD = -10.05cm, 95% CI = [-14.10,-6.00]); specific anatomical characteristics; and modified Mallampati's index or test (OR = 3.37, 95% CI = [2.07, 5.48]).

CONCLUSION: Our study made a comprehensive and systematic analysis of The DLE relevant factors. Gender, age, body mass index(BMI), neck circumference (NC), modified Mallampati's index(MMI), inter-incisor gap(IIG), hyoid-mental distance (HMD), thyroid-mental distance (TMD), sterno-mental distance (SMD), and flexion-extension angle were eventually identified as highly correlated factors for DLE.