[1] Med Res Inst New Zealand, Wellington, New Zealand
[2] Wellington Hosp, Capital & Coast Dist Hlth Board, Dept Resp Med, Wellington, New Zealand
[3] Wellington Hosp, Capital & Coast Dist Hlth Board, Dept Emergency Med, Wellington, New Zealand
[4] Capital & Coast Dist Hlth Board, Commun Hlth Serv, Wellington, New Zealand
[5] Univ Otago, Dept Med, Rehabil Teaching & Res Unit, Wellington, New Zealand