Funding for this research was provided by:
National Natural Science Foundation of China (No. 81372261, No. 81472309)
Received: 25 October 2018
Accepted: 8 March 2019
First Online: 30 April 2019
Ethics approval and consent to participate
: Ethical consent was not required in this study, since the MIMIC III data were analyzed namelessly.
: The manuscript does not include individual person’s data.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.