Sample size
An initial sample size of 488 patients was determined based on the
results of a retrospective study conducted from 2011 to 201516. According to the hypothesis that the intubation
rate with 5 cmH2O PEEP was 15% and that the application
of 10 cmH2O PEEP might reduce it by 50%, the study would have required
a sample of 244 patients in each arm to have a significance of 5% and a
power of 80%. Unfortunately, the study sites collected fewer patients
than initially planned. Due to the Coronavirus Disease-19 pandemic,
enrollments essentially stopped in 2020 due to resource limitations and
a significant decrease in bronchiolitis incidence. Hence, according to
Ethics Committee at the coordinating center (Bambino Gesù) and based on
the data available for the first patients (unplanned interim analysis),
the study was interrupted.