Eligibility criteria

Articles that meet the following eligibility criteria will be included: published between January 2002 and August 2021; studies conducted in developed countries; articles written in English or Japanese; randomised controlled trials, prospective/retrospective cohort studies or case-control studies; involved participants who were extremely premature infants born before 28 weeks of gestational age; and in which the endpoint was severe BPD classified by the NICHD definition. We will exclude descriptive research design studies as well as animal model and in vitro studies. We will also exclude studies that evaluated congenital airway diseases such as diaphragmatic hernia and congenital pulmonary airway malformations. This will enable us to restrict the objectives to BPD, which is, naturally, prematurity related. Protocols (a type of publication) will also be excluded from the analysis. We will omit studies with less than 500 participants to ensure the quality of literature included in this scoping review. In addition, we will focus more on the latest literature to reflect changes in pathophysiology and treatment of severe BPD.