Ratio of Height to Thyromental Distance And Ratio of Height to Sternomental Distance As Predictors of Difficult Airway in Adult Patients Undergoing Endotracheal Intubation.

Abstract

Background and objectives Failure to secure airway can lead to morbidity and mortality. In the present study, preoperative assessment of 131 patients posted for surgery under general anaesthesia was carried out to evaluate the usefulness of two predictive tests Ratio of Height to Thyro-mental distance (RHTMD) and Ratio of Height to Stern-omental distance (RHSMD) in predicting the ease or difficulty of tracheal intubation. Methods The study was a prospective single blinded observational study conducted in adult participants aged between 18 to 60 years scheduled for elective surgery under general anaesthesia. The preoperative airway assessment was conducted using two predictive tests Ratio of Height to Thyro-mental distance and Ratio of Height to Sterno-mental distance. Following induction of Anaesthesia laryngoscopy was performed and Cormack lehane laryngoscopy grade was noted. Intubation was considered difficult if the view on laryngoscopy was Cormack and Lehane grade III or IV, more than three attempts at tracheal intubation, duration of intubation longer than 10 minutes, failure to intubate or if special maneuvers were required to facilitate intubation. Sensitivity, specificity, Receiver operating Characteristic (ROC) curve analysis was performed using RHTMD and RHSMD for predicting difficult intubation. Results RHTMD has a Sn of 85.25%, Sp of 100% with 95% CI of 0.730 – 1.00 and a P value < 0.001 which is statistically significant. On ROC curve analysis the area under the curve for RHTMD is found to be 0.875. The optimal cut off value derived from ROC curve for RHTMD is 21.50cms. DocuSign Envelope ID: 0FC035C27409BE20-BEE96EE5-4402878-A95ADF9C--8A99960058B526E9976E7BD6 XV RHSMD has a Sn of 84.21%, Sp of 96.42% with 95% CI of 0.777 – 1.00 and a P value < 0.001 which is statistically significant. On ROC curve analysis the area under the curve for RHSMD is found to be 0.890. The optimal cut off value derived from ROC curve for RHSMD is 10.50cms. Conclusion • RHTMD is found to be a better predictor of difficult intubation and restricted laryngoscopic view as it is highly sensitive and 100% specific than RHSMD. On ROC curve analysis both RHTMD and RHSMD are found to be statistically significant without much difference in AUC. • The recommended cut off established by the study for RHTMD is 21.50cms and RHSMD is 10.50cms.