1. Department of Respiratory Medicine, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China
2. Medical College, Nankai University, Tianjin 300071, China
3. Nanlou Respiratory Disease Department, Chinese PLA General Hospital, Beijing 100853, China
4. Department of Respiratory Medicine, Guangzhou Women and Children Medical Care Center, Guangzhou, Guangdong 510623, China
5. Department of Critical Care Medicine, Chinese PLA General Hospital, Beijing 100853, China
6. Department of Medical Statistics, Chinese PLA General Hospital, Beijing 100853, China