1 Foundation Year 2 Doctor, Department of Respiratory Medicine, St Bartholomew's Hospital, London EC1A 7BE.
2 Medical Student, Queen Mary University London, London.
3 Foundation Year 2 Doctor, Department of Acute Medicine, Royal London Hospital, London.
4 Consultant Chest Physician, Department of Respiratory Medicine, St Bartholomew's Hospital, London and Honorary Senior Lecturer, Department of Health Sciences Education, Queen Mary University London, London.