[1] Edinburgh Napier Univ, Sch Hlth & Social Care, Edinburgh, Midlothian, Scotland
[2] Ostfold Univ Coll, Fac Hlth & Social Studies, Halden, Norway
[3] Univ Edinburgh, Dept Anaesthesia Crit Care & Pain Med, Edinburgh, Midlothian, Scotland
[4] Univ Edinburgh, Anaesthet Crit Care & Pain Med, Edinburgh, Midlothian, Scotland
[5] Univ Edinburgh, Edinburgh Clin Trials Unit, Edinburgh, Midlothian, Scotland
[6] GE Healthcare Finland Oy, Kuortaneenkatu 2, Helsinki 00510, Finland
[7] Ninewells Hosp, Dept Anaesthet, Nhs Tayside, Scotland
[8] Monklands Hosp, Dept Anaesthet, Nhs Lanarkshire, Scotland