Thyromental Height Test as a Method for Predicting Difficult Intubation in Patients with Obesity: A Prospective...

Background: Anthropometric tests and scales used to predict difficult intubation in people with obesity have limited sensitivity and specificity. A thyromental height test (TMHT) is based on the height between the anterior border of the thyroid cartilage and the anterior border of the mentum. Objectives: The aim of this study was to assess the usefulness of TMH in the prediction of difficult intubation in patients with obesity scheduled for elective surgical procedures. Methods: A prospective, observational cohort study in adult patients with BMI ≥ 30 kg⋅m^-2 scheduled for elective surgical procedures under general anesthesia, direct laryngoscopy, and intubation was conducted in a university hospital between June 2020 and June 2021. The primary outcome measure was thyromental height, and the secondary outcome measures were thyromental distance (TMD), sternomental distance (SMD), score in the modified Mallampati test (MMT), Cormack-Lehane grade (CL), neck circumference (NC), and mouth opening (MO) distance. As a secondary outcome, a composite score was developed and analyzed for its predictive performance. Results: In 77 patients (56 females, 72.7%) aged 43.21 ± 9.39 years with a mean BMI of 37.18 (34.6-42.8) kg⋅m^-2, difficult intubation was found in 18 patients (23.38%). Sleep apnea was present in 14 (23.75) patients with easy intubation vs. 9 (50%) patients with difficult intubation (p = 0.033). There were no statistically significant differences in thyromental height test, thyromental distance, neck circumference, and mouth opening scores. Male sex, TMD ≤ 175 mm, and MO ≤ 60.5 mm were predictors of difficult laryngoscopy. The OPERA Score (range 0-5) demonstrated superior predictive value (AUC = 0.8 p < 0.01), outperforming its individual components. Conclusions: Male sex, TMD ≤ 175 mm, and MO ≤ 60.5 mm are predictors for difficult laryngoscopy in patients with obesity. The results of our study indicate that TMH may not be a good predictor of difficult intubation in patients with obesity. However, when integrated into a composite score, it contributes meaningfully to a multifactorial risk assessment.