Received: 19 December 2016
Accepted: 22 March 2018
First Online: 2 April 2018
Ethics approval and consent to participate
: The study was considered a quality assurance project, which, according to Norwegian law on medical research, does not require an approval by the Regional Ethics Committee, nor a written patient consent. The Data Protection Authorities at Akershus University Hospital approved the study (reference number 13–106).
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.