Prediction of prolonged laryngoscopy

Duration of laryngoscopy must be kept as short as possible to prevent distu rbances of oxygenation and ventilation. Because the factors associated with prolonged laryngoscopy are not well known, we studied 1000 patients underg oing tracheal intubation under general anaesthesia to determine the possibl e effects of their characteristics on the incidence of prolonged laryngosco py (defined as lasting longer than 15 s). Multiple logistic regression anal ysis was performed to determine the odds ratio for significant factors. Pro longed laryngoscopy occurred in 158 patients (15.8%). Six characteristics w ere 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 extensi on < 70<degrees> [OR 7.1 (3.8-13.6)]. The presence of three of these factor s predicted prolonged laryngoscopy with a sensitivity of 0.72 and a specifi city of 0.91.