2.3-Power calculation
Several randomized, controlled studies comparing HFNCO and LFO have assessed changes in HR, RR, and CRS over time in children with bronchiolitis. However, we could not find a study comparing the time that HR and RR returned to the normal range for age and, similarly, the time for our CRS outcome mentioned. Therefore, we made a preliminary analysis and sample calculation by evaluating the data of 24 patients who met the study criteria. Sample size calculations were done using a t-test on primary outcomes to obtain a power of 90% and an alpha of .05. The sample size for HR and RR yielded 39 patients in each group, while the sample size for CRS yielded 50 subjects. Unfortunately, we did not reach the number of participants calculated with the power analysis because of the financial problem. So instead, we figured the effect sizes r of primary outcomes with the Mann-Whitney-U test interpreted as 0.1 small, 0.3 medium, and 0.5 large, according to the r = z/√n formula.22,23 The effect size for each of the primary outcomes was presented below the table.