Comparison of the STORZ CMAC video laryngoscope to standard direct laryngoscopy in a Pierre Robin manikin. Randomised crossover trial

Editor, Airway management in children with Pierre Robin syndrome is difficult even for experienced intubators, due to micrognathia, glossoptosis and airway obstruction.1 Many anaesthesiologists prefer video laryngoscopy over paediatric flexible fibreoptic bronchoscopy, currently being the gold standard due to unfamiliarity, unavailability and high costs.2 The STORZ CMAC (Karl Storz CMAC Video Laryngoscope; Karl Storz, Tuttlingen, Germany) has been successfully used in children with Robin sequence as well as in other case reports of difficult paediatric airways.3 A current guideline for the management of the difficult paediatric airway recommends the use of video laryngoscopy as a second choice once direct laryngoscopy (DL) fails.4 It is still unclear whether video laryngoscopy is superior to direct laryngoscopy in a child with Robin sequence in the hands of novice intubators. Twenty anaesthesia residents with limited paediatric airway experience were randomised to intubate a Pierre Robin manikin three times with a standard Miller 1 blade and a styletted 3.5- mm internal diameter (ID) oral endotracheal tube (group DL) and three times using the STORZ CMAC Miller 1 and a styletted 3.5 mm ID endotracheal tube (group video laryngoscopy). The Pierre Robin infant manikin (AirSim Pierre Robin X; TrueCorp, Belfast, Northern Ireland) features an anatomically correct 0 to 6-month old child with Pierre Robin based on real computed tomograph (CT) data. Time to intubate, time to best view (TTBV), successful placement of the endotracheal tube and percentage of glottic opening visualised were measured. A Mann–Whitney rank-sum test for nonnormal distributed data were used to compare the groups. P less than 0.05 was assumed statistically significant. Data are presented as median and interquartile range. Successful intubation was 96% with direct laryngoscopy (58/60) and 100% with video laryngoscopy (60/60). TTBV was significantly longer using direct laryngoscopy versus video laryngoscopy [DL median 8 s (interquartile range [IQR] 7 to 12) versus video laryngoscopy 6 s [4 to 8] P < 0.001] (Fig. 1). However, there was no difference in time to intubate between direct laryngoscopy [18 s (IQR 16 to 23)] versus video laryngoscopy (17 s [14 to 21]). The percentage of glottis opening score was significantly higher in video laryngoscopy compared with direct laryngoscopy (DL 45% [32.5 to 50]) versus video laryngoscopy (100% [90 to 100] P < 0.001) (Fig. 2).Fig. 1: Time to best view (s), median, interquartile range and 5 and 95% percentiles. ∗(P < 0.001). DL, direct laryngoscopy; VL, video laryngoscopy.Fig. 2: Percentage of glottis opening (POGO) percentage of glottic opening visualised (%), median, interquartile range and 5 and 95% percentiles. ∗(P < 0.001). DL, direct laryngoscopy; VL, video laryngoscopy.We were not able to demonstrate a statistically significant and clinically relevant difference in time to intubate. The significantly shorter TTBV using video laryngoscopy by 2 s is not clinically important. However, the significantly better view using video laryngoscopy is very likely clinically important and may increase the first attempt success rate and therefore reduce significant adverse events of prolonged intubation attempts. Hurford and White5 compared the STORZ DCI with another paediatric video laryngoscope in a paediatric manikin with a time to intubate of 18.8 versus 19.9 s, respectively, comparable with our findings. MacNair et al.6 found in 30 healthy children using the STORZ video laryngoscope a time to intubate of 19.3 s. The improved view using the STORZ CMAC is supported by clinical studies and also true to other types of video laryngoscopes in adults and children.7 Fiadjoe et al.2 compared the Glidescope video laryngoscope with flexible fibreoptic bronchoscopy in a Pierre Robin manikin. Their time to intubate of 25 s for the Glidescope video laryngoscope is longer than our median time to intubate of 17 s. This longer time to intubate may be due to the fact that the Glidscope video laryngoscope has an acute angle of the blade compared with the straight STORZ CMAC Miller blade and therefore prolongs placement of the tracheal tube. The time may have been measured differently. Also compared with experienced intubators, our residents may have not treated the manikin as a real child, risking more soft tissue trauma to achieve a shorter time to intubate. Our results of TTBV and time to intubate support the use of video laryngoscopy by novice intubators in potentially difficult paediatric airways. However, our measured success rate of 96% is much higher than the success rate in children with a congenital airway anomaly. This demonstrates that manikins are not ideal to study airway devices. Our study is also biased by other limitations of a manikin-based research and nonblinding. It was not able to measure potential airway trauma using direct laryngoscopy and intubators may have used more force than they would have with children using direct laryngoscopy. However, taking this into consideration, the difference in view to the glottis opening using video laryngopscoy may be even greater in humans. The results strengthen the role of video laryngoscopy as a tool in the difficult paediatric airway. In addition, video laryngoscopy can aid as a tool for teaching difficult airway management since the trainee and teacher share the same view to the airway. But it needs to be clearly emphasised that children with Pierre Robin syndrome, like any other children with expected difficult airway management, should be treated by experienced personnel exclusively. Acknowledgements relating to this article Assistance with this letter: we would like to thank Dr Christine Vlatten for her help with editing. Financial support and sponsorship: none. Conflicts of interest: none.

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