[1] Department of Anaesthesia, Royal Infirmary of Edinburgh, Edinburgh, EH3 9YW, Lauriston Place
[2] Frca, Department of Anaesthesia, Royal Infirmary of Edinburgh, Edinburgh, EH3 9YW, Lauriston Place
[3] Department of Anaesthesia, Royal Infirmary of Edinburgh, Edinburgh, EH3 9YW, Lauriston Place