1 Royal Free Perioperative Medicine Research Group, Royal Free Hospital, London, UK; University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK. Electronic address: daniel.martin@ucl.ac.uk.
2 University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK.
3 Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK.