Received: 3 June 2020
Accepted: 8 October 2020
First Online: 27 October 2020
Ethics approval and consent to participate
: The study was approved by the Ethical Committee of Shandong Provincial Chest Hospital. Written informed consent was waived by the Ethical Committee of Shandong Provincial Chest Hospital due to retrospective nature of the study. In addition, the data collected was anonymized before its use.
: Not applicable.
: We declare that we have no conflict of interest.