Discussion

 

 

In this clinical investigation, we evaluated the performance of the McGrath Video Laryngoscope (MVL) in 120 adult patients requiring orotracheal intubation for elective thyroid surgery. The operators were experienced with the use of video laryngoscopes and regularly obtained a view of the entire laryngeal aperture with the MVL despite conventional laryngoscopic views with visualization of only the epiglottis in 16 patients, intended by the study design.

 

Four patients required a second attempt for successful MVL-assisted tracheal intubation. The acute loss of battery power during laryngoscopy encountered in one patient cannot be validated as equipment malfunction because we did not pay attention to the low-battery warning on the left lower side of the video screen. We used the Schroeder directional tracheal tube stylet (DS) for articulating and passage of the tracheal tube (TT) through the laryngeal aperture; unfortunately, the DS was recently modified incorporating now a locking mechanism which impedes adjusted preshaping of the TT. Despite positioning the members of the DS in the posterior slot of the flange without using the locking mechanism, we encountered three primary failures of tracheal intubation due to the inability to advance the TT through the laryngeal aperture and minor problems and difficulties during laryngeal TT passage at successful tracheal intubation in 10 percent, the major challenge also experienced with other video laryngoscopes. Impeded TT advancement during tracheal passage (encountered in 4 percent) might have been due to the impingment 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; complete withdrawal of the DS and rotation of the TT 90 degree or more to the right enabled TT passage into the proper position.  

 

We observed minor problems and difficulties with fogging of the camera system (encountered in 9 percent) but not with impeded view due to the presence of secretions as the camera system is remote from the tip of the blade. Fogging is usually associated with optical and video systems not incorporating a warming-up mechanism, particularly when laryngoscopy and tracheal intubation are performed in an environment with a high-level air-condition as in our study. However, fogging of the camera system did not reduce the success rate of MVL-assisted tracheal intubation.    

 

The disposable laryngoscope blade (DLB) eliminates time-consuming cleaning and disinfection of the device and possible cross contamination and means that the MVL is always ready for use in other patients. Futhermore, the DLB was particularly suitable in patients with limited mouth opening and/or restricted pharyngeal space; the low profile of the DLB made blade insertion easy and provided enough space for oropharyngeal TT passage.

 

The adjustable camera stick is suitable for use in small and large adults, giving the operator maximum flexibility and avoiding problems with the selection of the appropriate size of the laryngoscope blade. This feature also obviates the sourcing of different blade sizes for particular patients or having to change the blades due to an irregular or unexpected airway anatomy.

 

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

 

Performed by experienced users of video laryngoscopes, the success of MVL-assisted tracheal intubation was not affected by conventional laryngoscopic view grading. The camera system and the blade were regularly well aligned with the laryngeal aperture when the MVL was properly inserted. Therefore, the MVL may be useful for routine and difficult laryngoscopy and tracheal intubation; however, further studies, particularly with operators less experienced with videolaryngoscopic techniques, are required to substantiate these suggestions.

 

 

References