Hip to Neck Circumference Ratio as an Independent Predictor of Difficult Intubation in Obese Patients

Background: Anaesthesiologists face difficult intubation (DI) more frequently in obese patients. Thus, we aimed to test if central obesity indices including hip circumference (HC), neck circumference (NC) or waist circumference (WC) can effectively predict DI and difficult mask ventilation (DMV) in them. Methods: HC, NC, WC, mask ventilation grade, intubation difficulty scale (IDS), history of snoring and obstructive sleep apnoea (OSA) were measured in 300 patients with BMI ≥ 30 kg/m2. Receiver operating characteristic curve (ROC) and multivariate, logistic regression were employed to identify predictors of DI (IDS ≥5) and DMV define as mask ventilation grade of 3 or 4. Results: DI and DMV were, respectively, detected in 14.7% and 12.7% of subjects. According to Multiple logistic regression analysis BMI (Odds ratio (OR):1.17, 95% confidence interval (CI): 1.08-1.28, p<0.001), NC (OR: 1.26, 95% CI: 1.04-1.52, p=0.01), HC (OR:1.06, 95% CI: 1.03-1.10) and HC/NC ratio (OR: 4.9, 95% CI: 1.64-14.92, p= 0.004) considered as independent predictors of DI. The same analysis recognized BMI (OR:1.13, 95% CI: 1.03-1.24, p=0.006), WC (OR: 1.06, 95% CI:1.01-1.11, p=0.01), and HC/BMI ratio (OR=0.18, 95% CI:0.06-0.53, p=0.002) as DMV predictors. Sensitivity of BMI >35.8 kg/m2, NC >39.9 centimetres (cm), HC>118cm and HC/NC ratio >2.9 were determined as 70.5%, 68.2%, and 69.3% respectively for prediction of DI. Sensitivity of BMI >36.6 kg/m2 and WC >118 cm for predicting DMV were identified as 71.0% and 73.6%. Conclusion: This study proposes to simultaneously consider the HC/NC ratio and WC as a predictor of difficult airway in the obese.