Martin Petzoldt has received a study grant from Verathon Inc., Bothell, WA, USA. Tim T. Hardel has received research support from Drägerwerk; Jörn Grensemann has received research support from Ambu and ETView, and consultant fees from Drägerwerk and GE HealthCare. The other authors declare no conflicts of interests.

Open Access funding enabled and organized by Projekt DEAL. The study was funded from departmental resources with the Vie Scopes kindly provided free of charge by the distributor.

This submission was handled by Dr. Stephan K. W. Schwarz, Editor-in-Chief, Canadian Journal of Anesthesia/Journal canadien d’anesthésie.