Received: 24 March 2020
Revised: 7 May 2020
Accepted: 26 May 2020
First Online: 4 June 2020
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: The authors study was approved by the local ethics committee (ethic committee of the medical faculty of the Heinrich Heine University Dusseldorf), and written informed consent was obtained from all volunteers.