A randomised, controlled crossover comparison of the C-MAC videolaryngoscope with direct laryngoscopy in 150 patients during routine induction of anaesthesia

Abstract

Background: The C-MAC® (Karl Storz, Tuttlingen, Germany) has recently been introduced as a new device for videolaryngoscopy guided intubation. The purpose of the present study was to compare for the first time the C-MAC with conventional direct laryngoscopy in 150 patients during routine induction of anaesthesia.

Methods: After approval of the institutional review board and written informed consent, 150 patients (ASA I-III) with general anaesthesia were enrolled. Computer-based open crossover randomisation was used to determine the sequence of the three laryngoscopies: Conventional direct laryngoscopy (HEINE Macintosh classic, Herrsching, Germany; blade sizes 3 or 4; DL group), C-MAC size 3 (C-MAC3 group) and C-MAC size 4 (C-MAC4 group) videolaryngoscopy, respectively. After 50 patients, laryngoscopy technique in the C-MAC4 group was changed to the straight blade technique described by Miller (C-MAC4/SBT).

Results: Including all 150 patients (70 male, aged (median [range]) 53 [20-82] years, 80 [48-179] kg), there was no difference of glottic view between DL, C-MAC3, C-MAC4, and C-MAC4/SBT groups; however, worst glottic view (C/L 4) was only seen with DL, but not with C-MAC videolaryngoscopy. In the subgroup of patients that had suboptimal glottic view with DL (C/L≥2a; n = 24), glottic view was improved in the C-MAC4/SBT group; C/L class improved by three classes in 5 patients, by two classes in 2 patients, by one class in 8 patients, remained unchanged in 8 patients, or decreased by two classes in 1 patient. The median (range) time taken for tracheal intubation in the DL, C-MAC3, C-MAC4 and C-MAC4/SBT groups was 8 sec (2-91 sec; n = 44), 10 sec (2-60 sec; n = 37), 8 sec (5-80 sec; n = 18) and 12 sec (2-70 sec; n = 51), respectively.

Conclusions: Combining the benefits of conventional direct laryngoscopy and videolaryngoscopy in one device, the C-MAC may serve as a standard intubation device for both routine airway management and educational purposes. However, in patients with suboptimal glottic view (C/L≥2a), the C-MAC size 4 with straight blade technique may reduce the number of C/L 3 or C/L 4 views, and therefore facilitate intubation. Further studies on patients with difficult airway should be performed to confirm these findings.

Figure 1

The portable C-MAC videolaryngoscope. The C-MAC videolaryngoscope, stored in the portable protective bag. Note the buttons for image recording on the monitor and the laryngoscope handle.

Figure 2

Comparison of C-MAC videolaryngoscopes with Macintosh laryngoscopes. Blade shapes of C-MAC videolaryngoscopes (top) and conventional Macintosh laryngoscopes (bottom) sizes 3 and 4, respectively.

Figure 3

Image capture of C-MAC laryngoscopic view. Image capture of videolaryngoscopic view with a C-MAC blade size 4 (formerly Cormack-Lehane class 3 view changed to class 1 view). Note the epiglottis that is uploaded on the blade tip (arrow; C-MAC4/SBT group).

Figure 4

Comparison of glottic visualisation between direct laryngoscopy and C-MAC videolaryngoscopy. Glottic visualisation according to Cormack-Lehane score after direct Macintosh laryngoscopy and C-MAC videolaryngoscopic views in the DL, C-MAC3, C-MAC4, and C-MAC4/SBT groups, respectively. Data are given as percentage. C/L indicates Cormack and Lehane view,[13] modified by Yentis and Lee;[14]DL: Direct laryngoscopy.

Figure 5

Glottic visualisation according to Cormack-Lehane score with direct laryngoscopy and C-MAC videolaryngoscopy. a) Best achievable Cormack-Lehane score (with external laryngeal manoeuvres, e.g. BURP) after direct laryngoscopy and C-MAC views in the DL, C-MAC3, C-MAC4, and C-MAC4/SBT groups, respectively. Data are given as percentage. C/L indicates Cormack and Lehane view,[13] modified by Yentis and Lee;[14]DL: Direct laryngoscopy. b) Improvement of Cormack-Lehane score in all patients with limited direct laryngoscopic view (DL group: C/L 3+4) after laryngoscopy with the C-MAC4/SBT (n = 8). Data are given as absolute numbers. C/L indicates Cormack and Lehane view,[13] modified by Yentis and Lee;[14]DL: Direct laryngoscopy.