Funding for this research was provided by:
Beijing Municipal Science & Technology Commission (Z141107002514143)
Text and Data Mining valid from 2020-01-07
Received: 9 January 2019
Accepted: 5 December 2019
First Online: 7 January 2020
Ethics approval and consent to participate
: The study was approved by the Institutional Ethical Committee of Aerospace Center Hospital. Patient informed consent for inclusion in this study was waived as it was an retrospective observational study.
: Not applicable.
: The authors declare that they have no competing interests.