1. Addenbrooke’s University Hospital, Cambridge, Cambridgeshire CB2 0QQ, UK
2. School of Medicine & Dentistry, Division of Applied Health Sciences, C/o Room 4013, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK
3. Department of Respiratory Medicine, Norfolk and Norwich University Hospital, Norwich, Norfolk NR4 7UY, UK
4. School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
5. School of Medicine & Dentistry, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK