Abstract No.: ABS3247 : Ratio of Height To ThyroMental Distance(RHTMD): A new predictor for assessment of difficult intubation in non-obese.

BACKGROUND & AIMS: The recognition of difficult intubation during preoperative checkup is very important for the anaesthesiologist. Various anatomical parameters assist in predicting difficult intubation. Till date, there are no predictors available to precisely asses the risk of difficult intubation pre-operatively. Therefore, we aimed to identify the adequacy of predictors for pre-operative assessment of difficult intubation. METHODS: After ethical approval, a total of 200 non-obese patients (body mass index ≤30) were recruited in this prospective observational study after obtaining informed consent. mouth opening (MO), modified Mallampati grade (MMG), neck circumference (NC), thyromental distance (TM), sternomental distance (SM), neck movements (NM) and Ratio of Height To ThyroMental Distance (RHTMD) were measured preoperatively. In each patient the validated intubation difficulty score (VIDS) was assessed intraoperatively by the anaesthetist. All patients were divided into two groups on the basis of easy (IDS Score <5) or difficult intubation (IDS Score ≥5). Multivariate logistic regression analysis including all variables was used to create a predictive model. RESULTS: Laryngoscopy was difficult in 12% of the patients. The MO, MMG, NM, NC, TM, SM, NC/TM were significantly different between easy and difficult intubation. AUROC for the TM , SM , NC/TM , RHTMD and MMG were 0, 270, 0.138, 0.848 , 0.807 and 0.699, respectively. Among all indices, NC/TM and RHTMD were found to have a high sensitivity and specificity. NC/TM had the maximum AUROC followed by RHTMD. CONCLUSION: Among non-obese patients, NC/TMD ratio and RHTMD are better predictors of difficult intubation pre-operatively.