ABSTRACT
BACKGROUND: The role of obesity as a risk factor for difficult intubation remains controversial. We primarily assessed the association between body mass index (BMI) and difficult tracheal intubation. METHODS: We analysed electronic records of more than 67 000 adults having elective non-cardiac surgery requiring tracheal intubation at the Cleveland Clinic between 2011 and 2015. The association between BMI and difficult intubation, defined as more than one intubation attempt, was assessed using multivariable logistic regression adjusting for pre-specified confounders. RESULTS: Amongst 40 183 patients with BMI <30 kg m-2 and 27 519 with BMI ≥30 kg m-2, 9% required more than one intubation attempt. Increasing BMI up to 30 kg m-2 was significantly associated with increased odds of more than one intubation attempt [odds ratio (OR): 1.03; 97.5% confidence interval (CI): 1.02, 1.04] per unit increase in BMI, P < 0.001. However, the odds of difficult intubation remained unchanged once BMI exceeded 30 kg m-2 (P = 0.08). The results were similar when analysis was restricted to patients without history of airway abnormalities in whom intubation was attempted using a standard direct laryngoscope (OR: 1.03; 99.4% CI: 1.01, 1.04) per kg m-2 increase in BMI <30 kg m-2). CONCLUSIONS: Increasing BMI was associated with increasing odds of difficult intubation in the lean range. At higher BMI, the odds of difficult intubation remain elevated, but there is no additional increase in odds with further increase in BMI. Obese patients were thus harder to intubate than lean ones, but difficult intubation was no more likely in morbidly obese patients than in those who were only slightly obese.