Robyn Smith, Consultant in Critical Care Medicine and Anaesthesia, West of Scotland Heart and Lung Centre, Golden Jubilee National Hospital, Glasgow, UK, Michael Higgins, Consultant in Critical Care Medicine and Anaesthesia, West of Scotland Heart and Lung Centre, Golden Jubilee National Hospital, Glasgow, UK, Alistair Macfie, Consultant in Critical Care Medicine and Anaesthesia, West of Scotland Heart and Lung Centre, Golden Jubilee National Hospital, Glasgow, UK