Correlation of Thyromental Distance with Cormack-Lehane Grading for PredictingDifficult Airway in Obese Adults (Code-T0316)

Introduction: Airway management is critical in anesthesia and emergency medicine, with
difficult intubation being a major cause of morbidity and mortality. Predicting a difficult airway
is essential for improving patient safety. The thyromental distance (TMD) is a commonly used
anatomical parameter, but its predictive accuracy in obese patients remains uncertain. This study
aims to assess the correlation between TMD and Cormack-Lehane (CL) grading in obese
patients to determine its reliability in predicting difficult airways.
Aims and Objectives
Aim:
To evaluate the efficacy of Thyromental distance which can predict difficult laryngoscopy and
intubation in obese patients undergoing elective surgery requiring general anesthesia, then to
compare and correlate the laryngoscopic grading obtained with the findings of airway assessment
test.
Objective:
To ascertain whether Thyromental distance measurement in obese patients correlates with
Cormack Lehane grading to predict difficult airway.
Methods: A prospective observational study was conducted on adult obese patients undergoing
elective surgery. TMD was measured preoperatively, and CL grading was recorded during
laryngoscopy. Statistical analysis was performed to assess the correlation between TMD, CL
grading, and other patient parameters, including BMI and ASA status.
Results: A moderate negative correlation was found between TMD and CL grading (r = -0.43, p
< 0.001), indicating that shorter TMD is associated with increased airway difficulty. Higher BMI
also correlated with more difficult laryngoscopy (r = 0.31, p < 0.001). TMD at a threshold of ≤5
cm showed high sensitivity (86.4%) but moderate specificity (44.4%) in predicting difficult
laryngoscopy.
Conclusion: TMD is a useful but moderate predictor of difficult airways in obese patients. A
combined approach using BMI and ASA status alongside TMD may enhance predictive accuracy
for difficult intubation.
Keywords: Thyromental distance, difficult airway, Cormack-Lehane grading, obesity,
laryngoscopy, airway assessment.