Department of Respiratory Medicine, The Second Affiliated Hospital, Dalian Medical University, Dalian, China; Department of Respiratory Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China. Electronic address: kybkyb2@163.com. Department of Respiratory Medicine, The Second Affiliated Hospital, Dalian Medical University, Dalian, China. Electronic address: wqdlmu@163.com.