Fraser 1977.

Methods	3‐factorial randomised controlled trial
Participants	Bilateral OME on tympanometry 85 children Aged 3 to 12
Interventions	Carnival blower 2 times a day or no treatment for 6 weeks Other arms (factorial design) received equal care except for the intervention
Outcomes	Pure‐tone audiometry Tympanometry (Both at 6 weeks) Adherence not reported
Notes	Also randomised to one, both or neither of Dimotapp elixir or 0.5% ephedrine nose drops
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No method of randomisation stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Comparability of groups at pre‐test	Low risk	"The comparability of patients in the groups which were to be compared after treatment was examined and no great differences were found between the patients in any of the groups"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	97% follow‐up
Selective reporting (reporting bias)	Low risk	No evidence of selective reporting