Howlin 2017.

Study characteristics
Methods	Double‐blind, placebo‐controlled RCT. Parallel design. Location: single centre in the UK. Duration: 20 days.
Participants	12 adolescents and young adults with CF. Age, mean (SD): NO group 30 (13.99) years; placebo group 29.3 (15.6) years. Gender split: not stated Baseline disease status: FEV1 % predicted, mean (SD): NO group 40.2% (20.14); placebo group 45.7% (18.28). FVC % predicted, mean (SD): NO group 54.4% (17.6); placebo group: 71.5 (21.11).
Interventions	Intervention group: NO gas (10 ppm; INOmax, 400 ppm mol/mol inhalation gas; INO Therapeutics) delivered via INOvent (Ikaria, supplied by INO Therapeutics), inhaled via nasal cannula for 8 h overnight for 5 – 7 days of therapy. Placebo group: air or air and oxygen mix, inhaled via nasal cannula for 8 h overnight for 5 – 7 days of therapy. Participants were followed up for the 7 days of therapy and at day 20.
Outcomes	Change from baseline in Ln CFU, FEV1 (% predicted), FVC (% predicted). Adverse events. Change in Paerugoinosa biofilm aggregates.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomisation with block lengths 2 and 4 was undertaken via an online randomisation service in a 1:1 ratio.
Allocation concealment (selection bias)	Low risk	Randomisation was undertaken via an online randomisation service to ensure concealment of treatment allocation.
Blinding (performance bias and detection bias) PUFA first	Low risk	Double‐blind trial; participants and outcome assessors were blinded to allocation. The placebo was administered via nasal cannula in the same way as the NO so that participants did not know whether they were getting NO or placebo. They also used sham weaning procedures.
Incomplete outcome data (attrition bias) All outcomes	Low risk	12 participants were randomised and all completed the trial and were included in the analysis.
Selective reporting (reporting bias)	Unclear risk	Not all of the outcomes specified in the trial registration document and methods were reported in the results. In the methods the authors state they will measure QoL via CFQ‐UK but there is no mention of this in the results or in any of the tables. Authors state that it is presented in the supplementary tables but we have not been able to locate these.
Other bias	Unclear risk	None identified.