Received: 22 November 2018
Accepted: 21 January 2019
First Online: 5 February 2019
Ethics approval and consent to participate
: The data was gathered from an anonymous national database. It was generated from a quality management initiative and the local ethics committee (Kantonale Ethik Kommission, KEK, Zurich) waived the necessity of ethical approval to conduct this study.
: Not applicable
: The authors declare that they have no competing interests.
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