1. Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
2. Department of Anesthesiology, Beijing Civil Aviation General Hospital, Beijing, China
3. Department of Anesthesiology, Beijing Huairou District Hospital of Traditional Chinese Medicine, Beijing, China
4. Department of Clinical Epidemiology and Tobacco Dependence Treatment Research, Beijing Chao-Yang Hospital, Capital Medical University, Beijing Institute of Respiratory Medicine, Beijing, China