1. Department of Respiratory and Critical Care Medicine, Shanxi Provincial People's Hospital, Taiyuan, Shanxi 030012, P.R. China
2. Department of Neurology, The Second Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, P.R. China
3. Department of Cardiology, Taiyuan Central Hospital, Taiyuan, Shanxi 030009, P.R. China
4. Department of Gynecology, Shanxi Provincial People's Hospital, Taiyuan, Shanxi 030012, P.R. China