1 Department of Dietetics, Guy's & St Thomas' NHS Foundation Trust, London, UK; Department of Critical Care, Guy's & St Thomas' NHS Foundation Trust, London, UK.
2 Institute of Health and Human Performance, University College London, London, UK; Division of Respiratory and Critical Care Medicine, University Medicine Cluster, National University Health System, Singapore; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
3 Lane Fox Respiratory Unit, Guy's & St Thomas' NHS Foundation Trust, London, UK; NIHR Biomedical Research Centre, Guy's & St Thomas' NHS Foundation Trust and King's College London, London, UK. Electronic address: Nicholas.Hart@gstt.nhs.uk.