[1] Great Western Hosp NHS Fdn Trust, Dept Anaesthesia, Swindon SN3 6BB, Wilts, England
[2] Resuscitat Council UK, Tavistock House North,TavistockSq, London WC1H 9HR, England
[3] Univ Hosp Birmingham NHS Fdn Trust, Dept Crit Care Med, Birmingham B9 5SS, W Midlands, England
[4] Univ Warwick, Warwick Med Sch, Warwick CV4 7AL, England