Effect of stylet angulation and endotracheal tube camber on time to intubation with the GlideScope®

Purpose: The GlideScope (R) videolaryngoscope usually provides excellent glottic visualization, but directing an endotracheal tube (ETT) through the vocal cords is sometimes difficult. The goal of the study was to determine which of two ETT angles (60 degrees vs 90 degrees) and cambers (forward vs reverse) was better, as determined by time to intubation (TTI). Methods: Two hundred patients requiring orotracheal intubation for elective surgery were randomly allocated to one of four groups: A) 90 degrees angle, forward camber; B) 90 degrees angle, reverse camber; C) 60 degrees angle, forward camber; D) 60 degrees angle, reverse camber. Time to intubation was assessed by a blinded observer. Operators were blinded until the point of intubation. A visual analogue scale (VAS) assessed the ease of intubation. The number of intubation attempts, number of failures, glottic grades, and use of external laryngeal manipulation were recorded. Results: The angle of the ETT had an impact on TTI but camber did not. The 90 degrees angle demonstrated a 13% faster 171 than the 60 degrees angle (47.1 +/- 21.2 sec vs 54.4 +/- 28.2 sec, P = 0.042), and it resulted in easier intubation (VAS 16.4 +/- 14.2 mm vs 27.3 +/- 23.5 mm, P = 0.0001). The overall incidence of a grade 1 or 2 Cormack-Lehane glottic view was 99%. Conclusions: In a heterogeneous group of operators and patients intubated with the GlideScope (R), a 90 degrees ETT angle provided the best result and should be the initial configuration. The camber of the ETT does not affect the time to intubation.