Baseline patient characteristics
| 2011 (n=115) | 2013 (n=165) | p Value | |
| Age, months, mean±SD | 2.70±2.57 | 2.17±2.23 | 0.07 |
| Gender, male (n (%)) | 64/115 (56) | 89/165 (54) | 0.78 |
| History of wheezing (n (%)) | 12/115 (10) | 15/165 (9.1) | 0.71 |
| Comorbidity (n (%)) | 13/115 (11) | 11/165 (6.7) | 0.17 |
| Prematurity <37 weeks of gestation (n (%)) | 14/115 (12) | 8/165 (4.9) | 0.03 |