Editorial Board: Antonio Anzueto (San Antonio, TX, USA), Leif Bjermer (Lund, Sweden), John R. Hurst (London, UK) and Carlos Robalo Cordeiro (Coimbra, Portugal). Managing Editors: Rachel White, Catherine Pumphrey and Ray Loughlin European Respiratory Society, 442 Glossop Road, Sheffield, S10 2PX, UK Tel: 44 114 2672860 | E-mail: monograph@ersj.org.uk Published by European Respiratory Society ©2017 June 2017 Print ISBN: 978-1-84984-085-9 Online ISBN: 978-1-84984-086-6 Print ISSN: 2312-508X Online ISSN: 2312-5098 Typesetting by Nova Techset Private Limited Printed by Ashford Colour Press Limited All material is copyright to European Respiratory Society. It may not be reproduced in any way including electronic means without the express permission of the company. Statements in the volume reflect the views of the authors, and not necessarily those of the European Respiratory Society, editors or publishers. Continuing medical education (CME) credits are available through many issues of the ERS Monograph. Following evaluation, successful Monographs are accredited by the European Board for Accreditation in Pneumology (EBAP) for 5 CME credits. To earn CME credits, read the book of your choice (it is clearly indicated on the online table of contents whether CME credits are available) then complete the CME question form that is available at www.ers- education.org/e-learning/cme-tests.aspx This journal is a member of and subscribes to the principles of the Committee on Publication Ethics