1. Department of Respiratory Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, PR China
2. Department of Thorax Medicine, the First Affiliated Hospital of Shenzhen University, Shenzhen, PR China
3. Department of Pulmonary and Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College &Chinese Academy of Medical Sciences, PR China
4. National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK