1. The First Department of Pulmonary and Critical Care Medicine, The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei 050000, P.R. China
2. Department of Gastroenterology, Hengshui People's Hospital, Hengshui, Hebei 053000, P.R. China
3. Department of Pulmonary and Critical Care Medicine, Hengshui People's Hospital, Hengshui, Hebei 053000, P.R. China