[1] Natl Univ Singapore, Yong Loo Lin Sch Med, 1E Kent Ridge Rd,NUHS Tower Block,Level 11, Singapore 119228, Singapore
[2] Duke NUS Med Sch, Prehosp & Emergency Res Ctr, Singapore, Singapore
[3] Duke NUS Med Sch, Program Hlth Serv & Syst Res, Singapore, Singapore
[4] Changi Gen Hosp, Dept Accid & Emergency, Singapore, Singapore
[5] Singapore Gen Hosp, Dept Emergency Med, Singapore, Singapore