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

Abstract

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.