To the left of the dashed line, the baseline and post-surfactant depletion OI (A) and VEI (B) values of all the animals featured in the study are given. To the right of the dashed line, the OI and VEI values of the different groups after 180 minutes of management with NIV are shown. Surfactant-treated groups are represented by the box-plots with a grey filling, whereas the groups treated with NIV only are represented by the white box-plots. The small squares within each box-plot indicate the mean of the group. The whiskers indicate the maximum and minimum values observed for each group. * P < 0.01 vs. any group not treated with surfactant; #
P < 0.01 vs. SNIPPV+SF group. NCPAP: nasal continuous positive airway pressure, SF: surfactant, NIPPV: nasal (non-synchronized) intermittent positive pressure ventilation, and SNIPPV: synchronized NIPPV.