1. College of Nursing, Qingdao University, Qingdao, Shandong 266003, P.R. China
2. Medicine Research Center, Weifang Medical University, Weifang, Shandong 261053, P.R. China
3. ICU, Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China