1. Cadre Ward (Geriatric), The First Hospital of Harbin, Harbin, Heilongjiang 150000, P.R. China
2. Department of Ultrasonography, Hongqi Hospital Affiliated to Mudanjiang Medical College, Mudanjiang, Heilongjiang 157000, P.R. China
3. Department of Thoracic Surgery, Hongqi Hospital Affiliated to Mudanjiang Medical College, Mudanjiang, Heilongjiang 157000, P.R. China
4. Intensive Care Unit, First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150000, P.R. China
5. Department of General Surgery, Hongqi Hospital Affiliated to Mudanjiang Medical College, Mudanjiang, Heilongjiang 157000, P.R. China