Received: 3 April 2019
Accepted: 1 July 2019
First Online: 12 July 2019
Ethics approval and consent to participate
: This study protocol was approved by the Ethical Committee of Hainan Medical College. Investigation procedures were approved by Hainan Medical College Institutional Committee.
: All authors of this paper consent for publishing manuscript and figures in the Journal.
: The authors declare that they have no competing interests.