Comparison 1. Bronchodilators compared to placebo for treatment of acute bronchiolitis.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Oxygen saturation measured by pulse oximetry: inpatient and outpatient settings	25	1242	Mean Difference (IV, Random, 95% CI)	‐0.43 [‐0.92, 0.06]
1.1 Inpatient studies	12	495	Mean Difference (IV, Random, 95% CI)	‐0.62 [‐1.40, 0.16]
1.2 Outpatient studies	13	747	Mean Difference (IV, Random, 95% CI)	‐0.25 [‐0.61, 0.11]
2 Sub‐analysis ‐ oxygen saturation (outpatients treated with albuterol/salbutamol)	10	572	Mean Difference (IV, Random, 95% CI)	‐0.19 [‐0.59, 0.21]
3 Improvement in clinical score (dichotomous)	7	365	Odds Ratio (M‐H, Random, 95% CI)	0.18 [0.06, 0.50]
3.1 Inpatient	5	208	Odds Ratio (M‐H, Random, 95% CI)	0.20 [0.05, 0.79]
3.2 Outpatient	2	157	Odds Ratio (M‐H, Random, 95% CI)	0.11 [0.01, 1.46]
4 Average clinical score after treatment: by treatment setting (continuous)	21	1086	Std. Mean Difference (IV, Random, 95% CI)	‐0.30 [‐0.54, ‐0.05]
4.1 Inpatient studies	9	416	Std. Mean Difference (IV, Random, 95% CI)	‐0.14 [‐0.41, 0.12]
4.2 Outpatient studies	12	670	Std. Mean Difference (IV, Random, 95% CI)	‐0.42 [‐0.79, ‐0.06]
5 Sub‐analysis ‐ average clinical score (outpatients treated with albuterol/salbutamol)	9	532	Std. Mean Difference (IV, Random, 95% CI)	‐0.36 [‐0.83, 0.11]
6 Hospital admission after treatment (outpatients treated with albuterol or salbutamol)	11	710	Odds Ratio (M‐H, Fixed, 95% CI)	0.75 [0.46, 1.21]
6.1 Nebulized	8	404	Odds Ratio (M‐H, Fixed, 95% CI)	0.77 [0.44, 1.33]
6.2 Oral in ED setting	1	37	Odds Ratio (M‐H, Fixed, 95% CI)	0.32 [0.03, 3.21]
6.3 Oral at home	2	269	Odds Ratio (M‐H, Fixed, 95% CI)	0.86 [0.28, 2.64]
7 Duration of hospitalization (inpatients)	6	349	Mean Difference (IV, Fixed, 95% CI)	0.06 [‐0.27, 0.39]
8 Time to resolution of illness (outpatients)	2	269	Mean Difference (IV, Fixed, 95% CI)	0.29 [‐0.43, 1.00]
9 Sensitivity analysis ‐ oxygen saturation low risk of bias studies	15	793	Mean Difference (IV, Random, 95% CI)	‐0.38 [‐0.75, 0.00]
9.1 Inpatient	4	210	Mean Difference (IV, Random, 95% CI)	‐0.65 [‐1.77, 0.48]
9.2 Outpatient	11	583	Mean Difference (IV, Random, 95% CI)	‐0.29 [‐0.66, 0.08]
10 Sensitivity analysis ‐ average clinical score low risk of bias studies	15	734	Std. Mean Difference (IV, Random, 95% CI)	‐0.22 [‐0.41, ‐0.03]
10.1 Inpatient	5	228	Std. Mean Difference (IV, Random, 95% CI)	0.01 [‐0.35, 0.37]
10.2 Outpatient	10	506	Std. Mean Difference (IV, Random, 95% CI)	‐0.32 [‐0.54, ‐0.09]
11 Sensitivity analysis ‐ average clinical score using RDAI (outpatients)	4	240	Std. Mean Difference (IV, Random, 95% CI)	‐0.11 [‐0.48, 0.25]