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

Abstract

CAN J ANESTH 54: 1 www.cja-jca.org Januar y, 2007Purpose: The GlideScope® 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° vs 90°) 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° angle, forward camber; B) 90° angle, reverse camber; C) 60° angle, forward camber; D) 60° 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° angle demonstrated a 13% faster TTI than the 60° 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®, a 90° ETT angle provided the best result and should be the initial configuration. The camber of the ETT does not affect the time to intubation. 'avec une angulation de 60° (47,1 ± 21,2 sec vs 54,4 ± 28,2 sec, P = 0,042), et l' intubation était plus facile (VAS 16,4 ± 14,2 mm vs 27,3 ± 23,5 mm, P = 0,0001

The GlideScope®-specific rigid stylet and standard malleable stylet are equally effective for GlideScope® use

“…[1][2][3]8 This study confirms the excellent glottic view that one regularly obtains with the GVL (Table II); 98% of patients had a grade I or II glottic view, 12 in agreement with previous work. 1,10,15 In this group of experienced GVL operators, there was no significant difference between the GRS and a standard malleable stylet for TTI or perceived ease of intubation. Although there was a trend towards shorter TTI with the malleable stylet, a larger trial would be required to reach statistical significance if the calculated point estimates are accurate, and the clinical relevance of a three-second shorter duration of intubation is debatable.…”

“…The endpoint of TTI was observation of end-tidal CO 2 on the anesthesia monitor, similar to other trials investigating intubation techniques. 10,15,16 This was done to be clinically meaningful and to provide an objective blinded endpoint. If the TTI had ended at ETT cuff inflation or GVL blade removal, the observer could have become unblinded watching stylet removal, which could have biased observations.…”

“…All operators were encouraged to practice with the GRS on mannequins and patients prior to study participation, but the malleable stylet with a 90° bend had the benefit of greater experience since it had become the local standard of care. 10 It is noteworthy that the GlideScope® is now available in a second-generation colour model with a slightly smaller blade profile, ~14 mm vs 18 mm, but similar shape and radius of curvature (GlideScope® Lo Pro Adult, Verathon Medical Inc., Bothell, WA, USA). During this trial, the first-generation GVL was used, and although it is unlikely that using the newer blade would result in clinically relevant differences in the results, the conclusions of this trial might not be applicable to the more recent design.…”

“…Each ETT was concealed so that the GVL operator would remain blinded until after GVL laryngoscopy had been completed, to avoid any potential bias during induction, GVL laryngoscopy or glottic view scoring. 10 Induction and maintenance of anesthesia were not standardized, but pre-oxygenation was mandated to an end-tidal oxygen concentration of ≥ 80% and all patients were paralyzed. The dosing of rocuronium or succinylcholine was at the discretion of the operator.…”

“…8 "Reverse loading" of the ETT on the stylet has also been proposed. 9 A randomized controlled trial involving malleable stylets showed that a stylet with a 90° bend resulted in faster intubation and perceived easier use than matching the GVL blade's 60° angle, 10 with no benefit from reverse loading.…”