1. Division of Nursing, University of the Ryukyus Hospital, Nishihara-cho, Nakagami-gun, Okinawa 903-0215, Japan
2. Division of Nursing, Japanese Red Cross Omori Hospital, Ota-ku, Tokyo 143-8527, Japan
3. Division of Nursing, Yamaguchi University Hospital, Minamikogushi, Ube 755-8505, Japan
4. School of Health Sciences, Yamaguchi University Graduate School of Medicine, Minamikogushi, Ube 755-8505, Japan