[1] Univ Warwick, Warwick Clin Trials Unit, Coventry CV4 7AL, W Midlands, England
[2] Heart England NHS Fdn Trust, Birmingham B9 5SS, W Midlands, England
[3] Kingston Univ London, Fac Hlth Social Care & Educ, London SW17 0RE, England
[4] St Georges Univ London, London SW17 0RE, England
[5] Southampton Univ Hosp, Resp BRU, Southampton SO16 6YD, Hants, England
[6] South Cent Ambulance Serv NHS Fdn Trust, Otterbourne, England
[7] Univ Bristol, Sch Clin Sci, Bristol BS8 1TH, Avon, England
[8] Royal United Hosp, Dept Anaesthesia & Intens Care Med, Bath BA1 3NG, Avon, England
[9] Univ Oxford, Nuffield Dept Orthopaed Rheumatol & Musculoskelet, John Radcliffe Hosp, Kadoorie Ctr Crit Care Res & Educ, Oxford OX3 9DU, England
[10] Monash Univ, Sch Publ Hlth & Prevent Med, Dept Epidemiol & Prevent Med, Melbourne, Vic, Australia
[11] Curtin Univ, Sch Nursing Midwifery & Paramed, PRECRU, Perth, WA, Australia
[12] St John Ambulance Western Australia, Belmont, MA, Australia
[13] West Midlands Ambulance Serv NHS Fdn Trust, Brierley Hill DY5 1LX, England
[14] North East Ambulance Serv NHS Fdn Trust, Newcastle Upon Tyne NE15 8NY, Tyne & Wear, England
[15] Welsh Ambulance Serv NHS Trust, St Asaph LL17 0RS, Denbigh, Wales
[16] London Ambulance Serv NHS Trust, 8-20 Pocock St, London SE1 0BW, England
[17] Univ Warwick, Warwick Med Sch, Stat & Epidemiol, Coventry CV4 7AL, W Midlands, England