1 Respiratory Medicine, University Hospitals of North Midlands NHS Trust, Stoke-on-Trent, UK abigail.mackintosh@nhs.net.
2 Royal Papworth Hospital NHS Foundation Trust, University of Cambridge, Cambridge, UK, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
3 Respiratory, Northumbria Healthcare NHS Foundation Trust, North Shields, Tyne and Wear, UK.
4 Imperial College Healthcare NHS Trust, London, England, UK.
5 Department of Respiratory Medicine, Royal Free London NHS Foundation Trust, London, UK.