Discussion

 

 

In this clinical investigation, we evaluated the GlideScope Ranger Video Laryngoscope (GRVL) for laryngoscopy and orotracheal intubation in 108 adult patients with a wide range of conventional laryngoscopic views requiring orotracheal intubation for elective thyroid surgery. Compared to the Lo Pro Adult GlideScope Video Laryngoscope (LGVL), the GRVL blade was significantly modified and released with a minituarized monitor. The operators were experienced with the use of the LGVL and readily obtained laryngeal views with adequate image quality of at least parts of the laryngeal aperture with the GRVL, despite laryngeal views at conventional laryngosopy (CL) with visualization of only the epiglottis or the soft palate, regarded as difficult CL, in 20 patients, intended by the study design. In the previous study with the LGVL (3), laryngeal views of at least parts of the laryngeal aperture were obtained in 99 of 105 patients with difficult CL. It should be noted that external laryngeal manipulation during laryngoscopy, not performed in both studies, might have improved the laryngeal views of at least one grade when optimum visualization of laryngeal structures not obtained. GRVL-assisted tracheal intubation was successful at the first atttempt; with the LGVL, the first-attempt success of tracheal intubation was 99 percent (437/442 patients) with successful tracheal intubation after a maximum of two attempts in all patients. These favorable results may not be obtained with CL techniques and limited tracheal intubation attempts.

 

In both studies, there were no problems and difficulties with blade insertion due to limited mouth opening and/or restricted pharyngeal space and poor visibility due to fogging of the camera system and/or the presence of secretion. The GRVL and the LGVL blade have a low profile with a maximum thickness of 16.5 and 14 mm, respectively, making blade insertion easy. The camera system of both laryngoscopes is resistant to fogging by warming-up the system slightly above body temperature within a short period of time as special feature; also secretions did not appear to interfere with the laryngeal view because the video camera is protected and remote from the tip of the blades.

 

Nevertheless, there were minor problems and difficulties with impeded advancement of the tracheal tube (TT) during oropharyngeal, laryngeal, and tracheal passage in both studies: in 8, 6, and 6 percent with the GRVL and in 2, 5, and 9 percent with the LGVL, respectively. The LGVL blade probably provided more space for oropharyngeal TT advancement than the GRVL blade. The shape of the TT is an important part of tracheal intubation with both video laryngoscopes; despite the routine use of the Schroeder directional tube stylet (DS) to remotely adjust the curvature of the TT during the tracheal intubation process, we again observed minor problems and difficulties with TT advancement through the laryngeal aperture, frequently associated with this technique of tracheal intubation. Impeded TT advancement into a midtracheal position might have been due to impingement of the TT on the anterior wall of the thyroid cartilage or the anterior trachea, but also due to tracheal deviation and/or compression by enlarged thyroid glands.

 

Severe complaints and injuries associated with airway management were not observed; this may be due to vizualization of at least parts of the laryngeal aperture during laryngoscopy and controlled TT advancement into a midtracheal position. In patients with difficult CL, conventional tracheal intubation, particulary after multiple attempts, may not provide these favorable results.

 

Performed by experienced LGVL users, the success of GRVL-assisted tracheal intubation was not affected by conventional laryngoscopic view grading as observed in the study with the LGVL. The GRLV together with the DS proved to be uniquely useful for routine and difficult laryngoscopy and tracheal intubation.

 

 

References