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Anesthesiology. 2009 Feb;110(2):266-74. doi: 10.1097/ALN.0b013e318194cac8.

High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database.

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  • 1Department of Anesthesia and Intensive Care Herlev, and Copenhagen Trial Unit, Centre of Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. lars_hyldborg@hotmail.com



Previous studies have failed to detect high body mass index (BMI) as a risk factor for difficult tracheal intubation (DTI). BMI was investigated as a risk factor for DTI in patients planned for direct laryngoscopy.


A cohort of 91,332 consecutive patients planned for intubation by direct laryngoscopy was retrieved from the Danish Anesthesia Database. A four-point scale to grade the tracheal intubation was used. Age, sex, American Society of Anesthesiologists physical status classification, priority of surgery, history of previous DTI, modified Mallampati-score, use of neuromuscular blocker, and BMI were retrieved. Logistic regression to assess whether BMI was associated with DTI was performed.


The frequency of DTI was 5.2% (95% confidence interval [CI] 5.0-5.3). In multivariate analyses adjusted for other significant covariates, BMI of 35 or more was a risk for DTI with an odds ratio of 1.34 (95% CI 1.19-1.51, P < 0.0001). As a stand alone test, BMI of 35 or more predicted DTI with a sensitivity of 7.5% (95% CI 7.3-7.7%) and with a predictive value of a positive test of 6.4% (95% CI 6.3-6.6%). BMI as a continuous covariate was a risk for failed intubation with an odds ratio of 1.031 (95% CI 1.002-1.061, P < 0.04).


High BMI is a weak but statistically significant predictor of difficult and failed intubation and may be more appropriate than weight in multivariate models of prediction of DTI.

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