All the chapters have been revised, new information on all the aspects has been incorporated by experts in the field. Contributing authors have revised the chapters to include recent advances. More tables, figures, algorithms, and recent references for further reading have been added. New chapters on COVID-19, whole lung lavage, airway malacias, lung complications in children with congenital heart diseases have been added. Chapters on imaging, airway clearances, and tuberculosis have been extensively updated.