Shinji Nakahara1, Ayako Taniguchi2, Tetsuya Sakamoto3. 1. Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan. Electronic address: snakahara-tky@umin.net. 2. Department of Risk Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan. Electronic address: taniguchi@risk.tsukuba.ac.jp. 3. Department of Emergency Medicine, Teikyo University School of Medicine, Tokyo, Japan. Electronic address: sakat@med.teikyo-u.ac.jp.