Randomisation and material
Stratified randomisation (physicians/nurses) was carried out using prepared and sealed envelopes in two groups. One group used VL (C-MAC®, Storz, Germany) with a Macintosh blade size 4, and the control group used DL with a Macintosh blade size 4. The groups used identical materials: VL (with external monitor), endotracheal tube size 7 with flexible tip and stylet (Parker Flex-Tip tube, Parker, USA) and ventilation bag (Spur II, Ambu, Germany). We deliberately chose to use a laryngoscope with an external monitor, although in everyday preclinical practice a device with a monitor on the handle is more likely to be used. This choice allowed standardisation for both groups (identical spatula and handle) and also allowed identical video analysis of the successful passage of the vocal cords for both groups. In the DL group, the monitor was swivelled out of the subject’s field of vision. All other conditions remained identical to the VL group. The manikin airway, tube and stylet were lubricated beforehand.After the conditions were explained and understood by the participant, the start of action was marked with a visual and acoustic countdown. Stopping chest compressions for intubation was not allowed. The study was carried out in a secluded room, and the study staff were not involved in the training of the individual study participants. To avoid any teaching bias, all participants underwent individual evaluation and other study participants were not allowed to watch.