Footnotes

• Contributors RJPGC, TC, OB-B and IA were involved in the concept, design and data acquisition. VK contributed to the formulation of the asthma bags. RJPGC wrote the initial draft, and TC, OB-B, IA and VK revised the draft and gave the final approval.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; externally peer reviewed.