1. Department of Respiration, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China
2. Department of Respiration, Dezhou People's Hospital, Dezhou, Shandong 253014, P.R. China
3. Department of Cardiology, Dezhou People's Hospital, Dezhou, Shandong 253014, P.R. China