1. Department of Pediatric Emergency and Critical Care Medicine Tokyo Metropolitan Children's Medical Center Tokyo Japan
2. Department of Clinical Epidemiology and Health Economics, School of Public Health The University of Tokyo Tokyo Japan
3. Division of Emergency and Transport Services National Center for Child Health and Development Tokyo Japan
4. Department of Pediatric Emergency Medicine Saitama Children's Medical Center Saitama Japan
5. Department of Pediatric Emergency Medicine Aichi Children's Health and Medical Center Obu‐shi, Aichi Japan
6. Department of Pediatrics Gifu Prefectural General Medical Center Gifu Japan
7. Department of Emergency Medicine, Massachusetts General Hospital Harvard Medical School Boston MA