Hollmann 1998.

Methods	Randomised, double‐blind, controlled, cross‐over study
Participants	13 infants (3 weeks to 23 months old) admitted to the PICU with RSV bronchiolitis RSV+, FiO2 < 50%, Criteria for inclusion: Bronchiolitis RSV+, with signs of lower respiratory tract disease Baseline characteristics, median (range): Age, mo 2.5 (3 wks to 24 mos) Clinical Asthma Score (m‐WCAS, maximum score of 10): 3.04 (1 to 7.5).
Interventions	Inhalation in a random order of heliox AND air‐oxygen, by non‐rebreather standard reservoir mask for two 20‐minute study periods
Outcomes	Primary endpoint: Clinical Asthma Score at 20 min Secondary endpoints: respiratory rate, heart rate and SpO2
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Coin tossing
Allocation concealment (selection bias)	Low risk
Blinding (performance bias and detection bias) All outcomes	Low risk	1 investigator was not blinded: the respiratory therapists; blinding was maintained by covering the on‐off valves to the air and helium sources with tape
Incomplete outcome data (attrition bias) All outcomes	Low risk	All patients completed the study and there were no losses to follow‐up, no treatment withdrawals 21 eligible patients were admitted during the study period. 3 patients were excluded from the study because of technical difficulties in setting up the gas delivery system (n = 1) and because of marked agitation (n = 2). 1 of the patients with agitation was intubated shortly after admission to the ICU. A total of 18 patients were studied, 13 of whom were randomised. Of the 13 randomised patients, 12 patients had Clinical Asthma Scores of < 6 and 1 patient had a Clinical Asthma Score of 7.5 but only mild signs of expiratory obstruction
Selective reporting (reporting bias)	Low risk	All results for outcomes were reported
Other bias	Low risk