Discussion

 

 

In this clinical investigation, novice users of the GlideScope Video Laryngoscope (GVL) successfully managed 334 adult patients with a wide range of conventional laryngeal views requiring orotracheal intubation for elective thyroid surgery. The operators first received formal hands-on training on a suitable airway model (5) for acquisition of sufficient skills in handling with the GVL and the Schroeder directional tracheal tube stylet (DS) for adjusting the curvature of the tracheal tube (TT) during the tracheal intubation process and were then instructed during the early series of performance on patients by an experienced user of the GVL. The operators found the transition to the GVL relatively seamless; laryngoscopy with the GVL closely resembles direct laryngoscopy with the Macintosh laryngoscope, so that the barriers associated with other advanced techniques of tracheal intubation did not exist.

 

The introduction of a new technique for airway management (AM) into clinical practice requires some time and preparatory steps: acquisition of available information about the technique, validation of the information, and most important, formal instruction before use in patients. We followed the educational concept initiated by Ovassapian (4) two decades before, that no operator should perform a new technical task for AM on patients without studying and developing the required base of knowledge involved in its performance on an airway model; this is due for established, for example, flexible bronchoscopes, and in particular, for newly introduced AM devices. The results of our study strongly support the initial use of an airway model for formal hands-on training. When the novice users of the GVL performed the first series of laryngoscopy and tracheal intubation attempts on patients, they were already familiar and confident with the technique.

 

The operators were very successful at visualizing the laryngeal aperture or at least the arytenoids with the GVL, despite conventional laryngoscopic views with visualization of only the epiglottis or just the soft palate encountered in altogether 76 patients, intended by the study design. It should be noted that external laryngeal manipulation during laryngoscopy, not performed in this study, might have improved the laryngeal views by at least one grade when optimum visualization of laryngeal structures not obtained. In 97 percent, GVL-assisted tracheal intubation was successful at the first attempt and performed in a timely fashion. The failure rate of laryngoscopy and tracheal intubation with the GVL in our study (only 10 of 334 patients required a second attempt for successful tracheal intubation) was much lower than in other studies evaluating the GVL (2, 6, 7). This may have resulted from prior hands-on training on an airway model, instruction during the early series of performance on patients, and the routine use of the DS. Simultaneous viewing of the entire laryngoscopy and tracheal intubation process by the operator and the instructor obviously accelerated the instruction. The number for obtaining acceptable clinical performance and competence with the GVL, estimated by the instructor, remained within 10 applications for all operators.

 

The shape of the TT is an important part of tracheal intubation with the GVL and determines the success or failure. Using TTs with prebended malleable stylets, the 60-degree curvature recommended by the manufacturer must be often increased. Inappropriate preshaping of the TT was the most frequent cause of difficulties with laryngeal TT passage in a recently published study evaluating the GVL on an airway model simulating easy and difficult laryngoscopy (3). Therefore, the DS with the advantage of adjusting the curvature as needed was routinely used in this study.

 

The unfamiliar technique of manipulating the TT while viewing the procedure on the monitor is easy to learn, but some training and practice is required to manipulate and direct the TT toward and through the laryngeal aperture into a midtracheal position. The relatively bulky GVL blade impeded TT advancement during oropharyngeal passage in 6 percent, as guidance of the TT through the oropharyngeal cavity requires an additional space. Impeded TT advancement through the laryngeal aperture (encountered in 15 percent) is adherent to this technique of tracheal intubation; distortion of the laryngeal aperture in the patient population investigated obviously contributed to this high incidence. Impeded TT advancement during tracheal passage (encountered in up to 11 percent) 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; compleate withdrawal of the DS and rotation of the TT 90 degree or more to the right usually enabled easy TT passage into the proper position.     

 

Frequent problems with fogging of the optical system usually encountered with rigid fiberoptic laryngoscopes (9, 10) were not evident. The camera system of the GVL is resistent to fogging by warming-up the system slightly above normal body temperature within a short period of time, a special feature of this device. Excessive secretions in the hypopharynx, also a major problem with the use of rigid fiberoptic laryngoscopes, may obscure the view with the GVL but does not reduce the success rate of tracheal intubation as the video camera is protected and remote from the tip of the blade.

 

With the GVL, tissues need not to be compressed and distracted with force and less traction on the temporomandibular joints is required in order to achieve a line-of-sight as frequently required with conventional laryngoscopy (CL). Therefore, less trauma may be expected and less stress is placed to the patient, particularly when CL and tracheal intubation are considered difficult. Severe complaints and injuries associated with AM were not observed; this may be due to vizualization of the laryngeal aperture or at least the arytenoids during successful laryngoscopy and controlled TT advancement into a midtracheal position.

 

Although flexible bronchoscopes are essential in difficult AM, they require different skills and an experienced assistance. The GVL is easy to use and the obscured view by soft tissue is usually controlled by the operator due to the blade design. Provided hands-on training on an airway model and instruction during the early series of performance on patients, novice users attained proficiency with GVL-assisted tracheal intubation within a short period of time.

 

 

References