Professor Ratjen is the Division Chief of Paediatric Respiratory Medicine at The Hospital for Sick Children, Professor of Paediatrics at The University of Toronto, and Senior Scientist at the Research Institute in the Department of Physiology and Experimental Medicine. He co-leads the cystic fibrosis centre at SickKids and is Medical Director of the Clinical Research Unit. He completed most of his medical education in Germany, along with a research fellowship at the Children's Hospital in Boston. He subsequently worked at the University of Essen, where he was appointed Deputy Chief of the Department of Paediatrics in 1998 and Professor of Paediatrics in 2001. Until 2005 he was the chief executive of the scientific board of the German CF Foundation before relocating in Canada in the same year. He is on the organizing committees of the major respiratory meetings (American Thoracic Society, European Respiratory Society and the North American CF conference), works on multiple grant review panels and is a member of the several editorial boards including the American Journal of Respiratory and Critical Care Medicine, Thorax, Pediatric Pulmonology and the Journal of Cystic Fibrosis.

His long-standing expertise in CF-related research and specifically the expertise and insight into the complexity of airway infection will help to guide the strategic vision of Cochrane CF. Over the years he has performed multiple studies assessing the impact of specific bacterial and fungal pathogens on the course of CF lung disease, but also in developing interventional strategies in CF. As such he has led and continues to lead early intervention studies on Pseudomonas eradication, disease modulation by addressing airway inflammation as well as intervention addressing the underlying ion channel abnormalities. Over the recent years I have also performed a number of studies to validate multiple breath washout technology as an early disease marker in CF including four studies involving hypertonic saline, dornase alfa and ivacaftor as well as more recently combination CFTR modulators as interventional strategies. I continue to conduct studies to better understand and treat infectious exacerbations in people with CF that are major drivers of lung function decline.