Evaluation of neck-circumference- thyromental- distance ratio as a predictor of difficult intubation: A observational study

Abstract

Background:
Difficult intubation poses a significant challenge in anesthesia practice, potentially leading to severe complications. Traditional predictors of difficult intubation, such as the Mallampati score and thyromental distance, have limitations. This study evaluates the neck-circumference thyromental-distance (NC/TMD) ratio as a novel predictor of difficult intubation in adult patients.
Materials and Methods:
This observational study was conducted on 200 adult patients scheduled for elective surgery
requiring general anesthesia with endotracheal intubation. Patients were assessed
preoperatively for neck circumference, thyromental distance, and NC/TMD ratio. The
difficulty of intubation was determined using the Cormack-Lehane grading system. Statistical
analysis was performed to evaluate the predictive value of the NC/TMD ratio, with a threshold
ratio determined for predicting difficult intubation.
Results:
Out of 200 patients, 30 (15%) experienced difficult intubation. The mean NC/TMD ratio was
significantly higher in the difficult intubation group (3.5 ± 0.6) compared to the easy intubation
group (2.7 ± 0.4) (p < 0.01). Receiver Operating Characteristic (ROC) curve analysis revealed
an area under the curve (AUC) of 0.82, indicating good predictive value. A NC/TMD ratio
threshold of 3.0 yielded a sensitivity of 80% and specificity of 75% for predicting difficult
intubation.
Conclusion:
The NC/TMD ratio is a valuable predictor of difficult intubation, offering a simple and reliable
assessment tool that could be integrated into preoperative evaluations. Further studies are
recommended to validate these findings across diverse populations and clinical settings.