Prediction of prolonged laryngoscopy

Duration of laryngoscopy must be kept as short as possible to prevent disturbances of oxygenation and ventilation. Because the factors associated with prolonged laryngoscopy are not well known, we studied 1000 patients undergoing tracheal intubation under general anaesthesia to determine the possible effects of their characteristics on the incidence of prolonged laryngoscopy (defined as lasting longer than 15 s). Multiple logistic regression analysis was performed to determine the odds ratio for significant factors. Prolonged laryngoscopy occurred in 158 patients (15.8%). Six characteristics were determined as risk factors for a prolonged laryngoscopy: weight > 80 kg [OR 3.7 (95% CI 1.9-7.1)]; tongue protrusion < 3.2 cm [OR 2.0 (1.0-4.2)]; mouth opening < 5 cm [OR 4.3 (2.1-8.9)]; upper incisor length > 1.5 cm [OR 4.2 (2.0-8.6)]; Mallampati class > 1 [OR 10.0 (7.1-14.6)]; and head extension < 70 degrees [OR 7.1 (3.8-13.6)]. The presence of three of these factors predicted prolonged laryngoscopy with a sensitivity of 0.72 and a specificity of 0.91