1 Warwick Clinical Trials Unit, University of Warwick, Coventry, UK, CV4 7AL; Heart of England NHS Foundation Trust, Birmingham, UK. Electronic address: [email protected].
2 Surrey Peri-operative Anaesthesia Critical care collaborative Research Group, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.
3 South Central Ambulance Service NHS Foundation Trust, Otterbourne, UK; University Hospital Southampton, Southampton, UK.
4 Warwick Clinical Trials Unit, University of Warwick, Coventry, UK, CV4 7AL.