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Medicine (Baltimore). 2018 Aug;97(34):e11984. doi: 10.1097/MD.0000000000011984.

Effect of the curved blade size on the outcomes of tracheal intubation performed by incoming interns: A randomized controlled manikin study.

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Department of Emergency Medicine, Bucheon St. Mary's Hospital.
Department of Emergency Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea.
Department of Emergency Medicine, School of Medicine, Hallym University, Kangdong Sacred Heart Hospital, Seoul.
Department of Emergency Medicine, Myongji Hospital, Goyang, Korea.



Novice clinicians who have little or no clinical experience in tracheal intubation occasionally need a long time to perform the procedure when using a large curved blade. They also have a lower tracheal intubation success rate, especially in emergency situations, such as cardiac arrest, than experienced practitioners. This study aimed to investigate whether the size of the curved laryngoscope blade affects the outcomes of tracheal intubation performed by incoming interns on a manikin model.


After completing a pre-study survey, the participants (n = 221) were randomly assigned into the following 2 groups based on the curved blade size: size 3 (n = 111) and size 4 (n = 110) curved blade groups. This study was conducted during a 1-day boot camp for incoming interns. The participants performed tracheal intubations using Macintosh laryngoscopes with size 3 or 4 blades on a Laerdal Airway Trainer (Laerdal, Stavanger, Norway). Subsequently, the participants were asked to complete a post-study survey. The primary outcome was the time to successful intubation (TSI). Meanwhile, the secondary outcomes were the first-pass and overall success rates, self-reported proximal esophagus visualization, and esophageal intubation. All intubation attempts were recorded and assessed by a trained assistant. The data were analyzed using the Mann-Whitney U or Chi-square test.


No significant differences in the baseline characteristics were observed between the 2 groups. The size 3 curved blade group had significantly shorter TSI than the size 4 curved blade group [25.0 (21.0-35.0) vs 36.5 (24.0-80.5) seconds, P < .001]. In addition, the size 3 curved blade group had significantly higher first-pass and overall success rates than the size 4 group (P = .001 and P = .005, respectively). Meanwhile, the size 4 curved blade group showed higher proximal esophagus visualization and esophageal intubation incidence rates than the size 3 curved blade group.


The outcomes of direct orotracheal intubation performed by novice practitioners may be influenced by the blade's size. Significant emphasis should be given on key anatomical landmarks and progressive visualization for tracheal intubation during airway management training for novice clinicians.

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