Is RHTMD a New Predictor for Assessment of Difficult Intubation in Non-Obese Patients?

Abstract

BACKGROUND The recognition of difficult intubation during pre-operative check-up is very important for the anaesthesiologist. Various anatomical parameters assist in predicting difficult intubation. Till date, there are no predictors available to precisely assess the risk of difficult intubation, pre-operatively.Therefore, we aim to identify the adequacy of predictors for preoperative assessment of difficult intubation. MATERIALS AND METHODSAfter ethical approval of Institutional Ethics Committee, a total of 200 non-obese patients (Body mass index less than or equal to 30) were recruited in this prospective observational study after obtaining informed consent. Mouth Opening (MO), Modified Mallampati Grading (MMG), neck circumference (cm), Thyromental Distance (TM), Sternomental Distance (SM), Neck Movement (NM), Neck Circumference (NC) and Ratio of Height to Thyromental Distance (RHTMD) were measured pre-operatively. In each patient, validated Intubation Difficulty Score (IDS score) was assessed intraoperatively by the anaesthetist. All patients were divided into two groups on the basis of easy (IDS score < 5) and difficult intubation (IDS score ≥ 5). Multivariate logistic regression analysis including all variables was used to create a predictive model. RESULTSLaryngoscopy was difficult in 12.0% of the patients. The MO, MMG, NM, NC, TM, SM, NC/TM were significantly different in between easy and difficult intubation. The Area Under Curve (AUC) in ROC for the TM, SM, NC/TM, RHTMD and MPC were 0, 270, 0.138, 0.848, 0.807 and 0.699, respectively. Among all indices, NC/TM and RHTMD were found to have high sensitivity and specificity. NC/TM was showing maximum area under the curve on ROC curve (AUC) followed by RHTMD. CONCLUSIONAmong non-obese patients, NC/TMD ratio and RHTMD can be used for better predictor of difficult intubation, pre-operatively.

2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway *

“…Observational studies reported comparative findings for facial and jaw features and anatomical measurement for difficult versus nondifficult airway patients as well as sensitivity, specificity, positive predictive, negative predictive, and accuracy values for difficult laryngoscopy and intubation. Findings for facial and jaw features, 7–11,13,14,18,27,33,38–40,42,43,45–47,49,51–54,57,58,64,68,123–159 anatomical measurements, 7–11,13–15,18,22,23,27–30,33,35,37–40,45–47,49,51–54,57,58,60, 64,65,68,70,123–132,134–154,156,158–203 and ultrasound anatomical measurements 69,139,162,170,194,196,203–213 were shown to have very high predictive and comparative variability, with sensitivity, specificity, and significance values ranging from low to very high across all patient measures (Category B2-E evidence). No single characteristic was identified as consistently being more predictive than another, and multivariate measures intended to predict difficult airways were too few and diverse among the studies to determine a common set of predictors.…”

Validation of Modified Mallampati Test with Addition of Thyromental Distance and Sternomental Distance to Predict Difficult Endotracheal Intubation in Adults Presenting in Surgical Emergency

“…Numerous airway assessment methods are in practice like Wilson risk score, head and neck movement, mouth opening or inter-incisor gap, thyromental distance, horizontal length of mandible, sternomental distance and mallampati test but sensitivities ranges upto 33% 7 . Few studies are available on combination of these methods to assess the predictive values like upper lip bite and thyromental distance [8][9][10] . This study aims to evaluate validation of MMT by adding SMD and TMD in prediction of difficult intubation or laryngoscopy in surgical patients.…”