[Direct laryngoscopy or C-MAC video laryngoscopy? Routine tracheal intubation in patients undergoing ENT surgery].Anaesthesist. 2010 Sep; 59(9):806-11.A
Previous studies have shown that video laryngoscopy enhances laryngeal view in patients with apparently normal and difficult airways. The utility of the novel, portable, battery-powered C-MAC video laryngoscope is as yet unproven. It was hypothesized that in routine patients undergoing ENT surgery, the rate of glottic views considered unsatisfactory, i.e. Cormack and Lehane grades IIb, III, and IV, could be significantly reduced with the C-MAC video laryngoscope compared to direct laryngoscopy.
Following ethical approval and sample size estimates 108 consecutive patients undergoing ENT surgery under general anesthesia were studied. First, direct laryngoscopy was performed with the naked eye. The best view obtained was graded by the first anesthesiologist without looking at the video monitor. A second anesthesiologist blinded to the laryngeal view obtained under direct laryngoscopy graded the laryngeal view on the video monitor. Endotracheal intubation using Ring-Adair-Elwyn (RAE) tracheal tubes was then attempted under video-aided visualization. The tubes were not reinforced with a stylet. The C-MAC video laryngoscopy system (Karl Storz, Tuttlingen, Germany) is a novel device that can be used with Macintosh laryngoscope blades in different sizes. A camera and light source are located recessed from the tip of the blade. The camera unit sits in a handle attached to the laryngoscope blade and is connected by a wire to a TFT video monitor. It allows for both direct and indirect laryngoscopy and the low profile of the original British Macintosh blades may prove advantageous in patients with limited mouth opening.
A total of 108 patients were enrolled in the study but for various reasons only 94 completed the study (post hoc power 97%). In 89 patients a size 3 Macintosh laryngoscope was used while a size 4 blade was used in the remaining 5 patients. With direct laryngoscopy the glottic view was considered unsatisfactory in 40 patients (42%), but this was the case in only 15 patients (16%) when video laryngoscopy was used (p<0.0001). Endotracheal tube placement was successful in all but one patient where the Bonfils intubation fiberscope needed to be employed. No complications related to the C-MAC system were observed.
Compared to direct laryngoscopy with a Macintosh laryngoscope blade in unselected patients undergoing ENT surgery and thus patients more susceptible to an unexpected difficult airway than a general patient population, the mobile C-MAC video laryngoscope significantly enhanced laryngeal view. Using RAE tracheal tubes seems to compensate the unfavorable deviation of optical and anatomical axes when indirect laryngoscopy is performed with the C-MAC system.