Stephen J. Chapman is Consultant in Respiratory Medicine at Oxford University Hospitals NHS Foundation Trust, Oxford, UK. Grace V. Robinson is Consultant in Respiratory Medicine at Royal Berkshire NHS Foundation Trust, Reading, UK. Rahul Shrimanker is Specialist Registrar in Respiratory Medicine at Severn Rotation, UK. Chris D. Turnbull is Clinical Lecturer in Respiratory Medicine at the University of Oxford, Oxford, UK. John M. Wrightson is Consultant in Respiratory Medicine at Oxford University Hospitals NHS Foundation Trust, Oxford, UK.