Fiona M Ratcliffe1, Rajesh Kharbanda2, Pierre Foëx3. 1. Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford, UK. Electronic address: fiona.ratcliffe2@ouh.nhs.uk. 2. Department of Cardiology, John Radcliffe Hospital, Oxford, UK. 3. Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford, UK.