Received: 26 February 2020
Accepted: 4 June 2020
First Online: 22 June 2020
Ethics approval and consent to participate
: This study was approved by the first affiliated hospital of Chongqing medical university. Because of the retrospective design of this study, the exemption for the informed consent for each participant was granted by the Ethical Review of the first affiliated hospital of Chongqing Medical Ethics Committee. This study was carried out in accordance with the principles of the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.