1. Division of Critical Care, Shonan Kamakura General Hospital, Kanagawa, Japan
2. Terumo Corporation R and D Center, Shonan Center, Ashigarakami-gun, Kanagawa, Japan
3. Department of Health Services Research, University of Tsukuba, Ibaraki, Japan
4. Health Services Research and Development Center, University of Tsukuba, Ibaraki, Japan
5. Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, UK