Editorial Board: Mohammed AlAhmari (Dammam, Saudi Arabia), Sinthia Bosnic-Anticevich (Sydney, Australia), Sonye Danoff (Baltimore, MD, USA), Randeep Guleria (New Delhi, India), Bruce Kirenga (Kampala, Uganda), Silke Meiners (Munich, Germany) and Sheila Ramjug (Manchester, UK). Managing Editor: Rachel Gozzard European Respiratory Society, 442 Glossop Road, Sheffield, S10 2PX, UK Tel: 44 114 2672860 | E-mail: monograph@ersnet.org Production and editing: Caroline Ashford-Bentley, Alice Bartlett, Alyson Cann, Claire Marchant, Catherine Pumphrey, Kay Sharpe and Ben Watson Published by European Respiratory Society ©2021 September 2021 Print ISBN: 978-1-84984-139-9 Online ISBN: 978-1-84984-140-5 Print ISSN: 2312-508X Online ISSN: 2312-5098 Typesetting by Nova Techset Private Limited Printed by Page Bros Group Ltd, Norwich, UK 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.