DOI: https://doi.org/10.53350/pjmhs22161612 ORIGINAL ARTICLE 612 P J M H S Vol. 16, No.01, JAN 2022 Diagnostic Accuracy of Neck Circumference and Thyromental Distance Ratio for Assessing Difficult Intubation in Obese Patients: a Validation Study SANA IMTIAZ 1 , MADIHA ZAFAR 2 , MARIAM WAHEED 3 , LALA RUKH BANGASH 4 VARDA BALOCH 5 , MUBASHRA HAMZA 6 1 Senior Registrar, Lahore general hospital 2 Assistant professor, Department of Anesthesia, Mayo hospital, Lahore 3 Senior registrar, Department of Anesthesia Mayo hospital, Lahore 4 Assistant professor, Jinnah burn and reconstructive surgery center 5 Assist. Professor Anesthesiology, Pakistan Ordanance Factories Hospital, Wah medical college. 6 Consultant Anesthetist, DHQ nankana Correspondence to: Madiha Zafar, Email: dr.madihazafar@hotmail.com, Cell: 03017794663 ABSTRACT Various tools for airway assessment are include Mallampati score, upper lip bite test, Wilson scoring and extent of mouth opening; none have high investigative precision especially in obese patients. Objectives: To assess the diagnostic accuracy of neck circumference and thyromental distance ratio for assessing difficult intubation in obese patients using intubation difficulty score as gold standard. Setting: Department of Anesthesiology in East and West operation theatres of Mayo hospital Lahore. Duration: 12 months (From Oct 2015 – Oct 2016) Sample Size: 220 obese patients Methods: Patients undergoing elective surgery were enrolled. Height, weight and body mass index was documented. At the cricoid cartilage level, the neck circumference was measured. All tracheal intubations were conducted by a three-year-experienced anaesthesiologist who was unaware of the study's findings. Cormack and Lehane's grading system was used to rate the laryngoscopy image. Difficult intubation was assessed according to intubation difficulty scoring. Results: The diagnostic accuracy of neck circumference and thyromental distance ratio in assessment of difficulty intubation (DI) among obese patients was 47%, sensitivity 85% and specificity of 37%. Conclusion: NC/TM ratio was a good interpreter in assessing difficult intubation in obese patients. This variable can be incorporated in our preoperative assessment for difficult intubation (DI). It is simple, requires very less time and is economical. Keywords: Airway management, obese, difficult intubation, neck circumference, laryngoscopy, tracheal intubation. INTRODUCTION It is the responsibility of anesthesiologist to maintain airway and ensure adequate ventilation during the course of general anaesthesia. 1 Maintaining ventilation with facemask or artificial airway device can be tough especially in patients with atypical facial features. Difficult intubation or ventilation is usually seen in patients with abnormal facial features like receding mandible, sunken cheeks, edentulous buck teeth, large bull neck, narrow mouth opening, obesity or facial or neck pathology. 2 An intubation is considered hard if it takes more than three tries or more than ten minutes for a normally trained anesthesiologist to achieve a fruitful endotracheal intubation. Restricted laryngoscopic view of vocal cords is presented according to Cormack-Lehane’s scoring. Various alternative techniques and adjuncts are required for this intubation. 2 Unable to intubate and ventilate can result in inadequate oxygen delivery to brain resulting in hypoxic brain injury or even brain death. 3 Maintenance of airway in obese patients is demanding. Obese individuals are more prone to have short, swollen necks, making mask ventilation and direct laryngoscopy more difficult. Partially obstructed airways are more likely due to the greater volume of soft tissues in the upper airway. 4 Adequate preoperative assessment and planning regarding airway management is necessary. Various tools for airway assessment have been devised which include Mallampati score. 2,3 History of obstructive sleep apnea syndrome (OSAS) 4 , short neck, improved age, male sex and high BMI 5 (˃30kg/m 2 ) are contributory factors in airway difficulty. 6 But none have high diagnostic accuracy especially in obese patients. 5 The purpose of the study was to establish a predictor which is easy to perform and has high sensitivity and specificity especially in obese patients. This would establish a predictor which was easy to perform, had few predictors and had high sensitivity and specificity. So far no study has been conducted in Pakistan regarding this topic so I tested its accuracy in my population. Studies are available in the literature on neck circumference and thyromental distance separately but I could find only one study based on this ratio. So my study added bulk to the already existing literature. MATERIALS AND METHODS In this cross sectional validation study designed to assess the diagnostic accuracy of neck circumference and thyromental-distance ratio in predicting difficult intubation in obese patients using intubation difficulty score, patients of age 18-60 years of either gender and of ASA class 1 or 2