Fig. 2: Trajectories of S/F ratio in responders and nonresponders to surfactant therapy.

Box-and-whisker plots show median, interquartile range, and range of S/F ratio over time. The horizontal lines mark the S/F threshold of 428 (SpO₂ = 90% at FiO₂ = 0.21). Changes over time were assessed by repeated measures ANOVA with Bonferroni post-test.