Article History
Received: 22 October 2018
Accepted: 6 January 2019
First Online: 6 February 2019
Ethics approval
: Not applicable as this is a review and meta-analysis. Trials meta-analysed have all received their original ethical approval.
: Not applicable
: A/Prof. D. De Luca has received grants for research and educational projects from Chiesi Pharmaceuticals spa and ABBVIE inc. He also received travel grants from ABBVIE inc. He served as consultant and lecturer for both Chiesi Pharmaceuticals spa and ABBVIE inc. Finally, he has been member of the external advisory board for both Chiesi Pharmaceuticals spa and ABBVIE inc. These companies produce two surfactants analysed in the paper, but they had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, approval of the manuscript or decision to submit it for publication. The other authors declare no competing interests.
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