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. 2020 Nov 19;4(1):e000858. doi: 10.1136/bmjpo-2020-000858

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© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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PRISMA flow diagram. Qualitative refers to qualitative assessment of the study methodology and quantitative is the number of studies included in the meta analysis. NIV, non-invasive ventilation; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses; RCT, randomised controlled trial; SR, systematic review.