University of Oxford - Respiratory Medicine Unit, University of Oxford - Nuffield Department of Clinical Medicine, University of Padova - Department of Cardiac, Thoracic, Vascular Science and Public Health, University of Oxford - Respiratory Medicine Unit, University of Southampton - School of Clinical and Experimental Sciences, University of Southampton - School of Clinical and Experimental Sciences, University of Southampton - School of Clinical and Experimental Sciences, Government of the United Kingdom - Portsmouth Hospitals NHS Trust, University of Oxford - National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), Government of the United Kingdom - Portsmouth Hospitals NHS Trust, University of Oxford - Nuffield Department of Clinical Medicine, University of Oxford - Respiratory Medicine Unit, University of Southampton - School of Clinical and Experimental Sciences and University of Oxford - Respiratory Medicine Unit