The influence of morbid obesity on difficult intubation and difficult mask ventilation

To determine the influence of morbid obesity on the incidence of difficult mask ventilation and difficult intubation.

Over a 6-year period, all tracheal intubations in the operating room of a large tertiary teaching hospital were analyzed. A modified version of the intubation difficulty scale (mIDS) was used to define easy versus difficult intubation, where a score of two or greater was defined as difficult intubation. Difficult mask ventilation was defined as the use of one or more adjuncts to achieve successful mask ventilation.

Of 45,447 analyzed cases, 1893 (4.2%) were classified as difficult intubations. Morbidly obese patients were not more likely to have difficult intubation [Odds Ratio (OR) = 1.131, 95% confidence interval (CI): 0.958, 1.334, p = 0.146]. Factors that were associated with difficult intubation included patient age > 46 years, male sex, Mallampati 3-4, thyromental distance < 6 cm, and the presence of intact dentition. Of 37,016 cases in which mask ventilation was attempted, 1069 (2.9%) were difficult. Morbidly obese patients were more likely to have difficult mask ventilation (OR = 3.785, 95% CI: 3.188, 4.493, p < 0.0001). Other factors associated with difficult mask ventilation included patient age > 46 years, male sex, Mallampati 3-4, and a history of obstructive sleep apnea. Having intact dentition decreased the likelihood of difficult mask ventilation.

Morbidly obese patients do not have a higher incidence of difficult intubation compared to non-morbidly obese patients. However, they have a significantly higher incidence of difficult mask ventilation. Other factors that are predictive of both difficult mask ventilation and difficult intubation include age > 46 years, male sex, and Mallampati 3-4.