Unanticipated difficulties during tracheal intubation are related to perioperative morbidity and mortality, but the success of direct laryngoscopic intubation depends largely on clinician's experience and the upper airway anatomy. The lightwand was introduced as alternative intubation technique, but the indicators of difficult lightwand intubation (DLWI) have not been identified. Accordingly authors conducted this study to identify subject factors that affect DLWI, and to compare these with those of difficult laryngoscopic intubation.

Seventy-three healthy subjects requiring tracheal intubation for elective surgery were enrolled. Anatomic factors, such as, body mass index (BMI), Mallampati classification (MC), inter-incisor gap, thyromental distance, neck circumference, extent of head and neck motion, and Cormack-Lehane grade (CL) were determined and evaluated in terms of their abilities to predict DLWI, which was described using intubation time and number of intubation attempts. Multiple regression analyses were performed to identify predictors using a variable selection technique.

Only MC and BMI were found to predict DLWI. The weighted sum of time and number of attempts (r² = 0.854, P = 0.000) was found to be better predictor of DLWI than their product (r² = 0.734, P = 0.000). Cormack-Lehane grade was not found to be significantly related to DLWI (P = 0.093).

Of the anatomic factors examined, only Mallampati classification and body mass index were found to predict difficult lightwand intubation.