Factors influencing time of intubation with a lightwand device in patients without known airway abnormality

Abstract

Study objective: To evaluate the correlation between accepted screening tests for difficult tracheal intubation and ease of intubation with a lightwand blind technique.

Design: Prospective study.

Setting: Anesthetic rooms of a university hospital.

Patients: 122 female, ASA physical status I, II, and III patients requiring tracheal intubation for elective surgery.

Interventions: After receiving a standardized anesthetic induction, patients first underwent direct laryngoscopy to determine Cormack laryngoscopy grade, then tracheal intubation was performed using a transillumination method.

Measurements and main results: Patient demographics, Mallampati class (MC), mouth opening (MO; cm), and thyromental distance (TMD; cm) were all measured and the values recorded. Body mass index (BMI; kg/m2) was calculated for each patient. Laryngoscopy grades obtained by laryngoscopy were also recorded. Times to intubation were measured by a chronometer and failures were recorded. Patients were then allocated to groups according to the measured parameters: BMI > or = 30 kg/m2, BMI < 30 kg/m2; TMD > or = 6 cm, TMD < 6 cm; MO > or = 3, MO < 3; MC I, MC II, MC III, MC IV, and Laryngoscopy Grade (LG) 1, LG 2, LG 3, LG 4. Intubation times at the first attempt were compared within the groups for each variable. The total results of 119 patients were studied; overall success was 99%, and mean time to intubation at the first attempt was 9.2 +/- 4.9 seconds. Although time to intubation was prolonged with increasing Mallampati and laryngoscopy scores, and in the TMD < 6 cm and BMI > or = 30 kg/m2 groups, only the MC III and BMI > or = 30 kg/m2 groups represented a statistically significant difference of prolongation. Mean time to intubation in the MC III and BMI > or = 30 kg/m2 groups were 13.2 +/- 5.4 (p = 0.011) and 14.8 +/- 1.7 (p < or = 0.001), respectively.

Conclusion: Mallampati class III airway significantly increases time to intubation when the transillumination technique is used. BMI > or = 30 kg/m2 is another factor that interferes with the ease and success of intubation with this technique.