Neck Circumference Is An Effective Tool For Predicting Difficult Intubation In Obese Patients

Background: The risk of difficult intubation in obese patients and preoperative prediction is fundamental to safe anaesthesia. Neck circumference is documented to be an important and reliable predictor in obese patients.Objective: To compare the effectiveness of neck circumference (NC), modified Mallampati test (MMT), thyromental distance (TMD), sternomental distance (SMD) and inter-incisor gap (IIG) in predicting difficult intubation between obese and non-obese patients.Patients and methods: One hundred and fifty six healthy patients; obese (Group OB n=78), body mass index (BMI)>30kg/m2 and non-obese (Group NO, n=78) aged 18-60years scheduled for elective surgical procedures under general anaesthesia, had their height, weight, NC, MMT, TMD, SMD and IIG measured. Intubation difficulty scale (IDS) >5 was categorized as difficult intubation and =5 categorized as easy intubation.Results: In the obese patients NC =40cm (OR-5.9, 95% CI:1.18–29,4) and MMT=3 (OR-18.7, 95% CI:3.56-97.1) were the most effective predictors of  difficult intubation. In non-obese patients MMT=3 (OR - 8.0, 95% CI:1.38-46.5) and IIG=4cm (OR 35.5, 95% CI:2.62-479.0) were the most effective predictors of difficult intubation. Neck circumference was the only predictor that was significantly different between both groups (p<0.05). The risk of difficult intubation in obese patients with NC =40cm was 50 times higher compared to non-obese patients (p=0.011). Neck Circumference had a moderate correlation (r-0.409, p<0.001), BMI a weak correlation (r-0.240 p=0.034) and weight a very poor correlation (r-0.092 p=0.421) with difficult intubation.Conclusion: Neck circumference is a better predictor and tool for assessing obesity as a risk factor for difficult intubation. Keywords: Difficult intubation, Obese, Non-obese, Airway assessment, Neck circumference