Abstract To describe and assess diaphragmatic function by ultrasound during the weaning and post-extubation phases in preterm newborns. This cross-sectional study included intubated preterm newborns eligible for extubation. Inspiratory diaphragmatic thickness (IDT), expiratory diaphragmatic thickness (EDT), diaphragmatic thickening fraction (DTF), and diaphragmatic excursion (DE) were evaluated at three time points: T1—during invasive mechanical ventilation (IMV); T2—during the spontaneous breathing trial (SBT); and T3—during nasal intermittent positive pressure ventilation (NIPPV). Friedman test and Wilcoxon signed-rank post hoc test were used for comparisons ( p < 0.05). Fifty preterm newborns were evaluated. Forty-five (mean gestational age 30.9 ± 2.2 weeks; mean weight 1377.5 ± 432 g) received IMV for 4 ± 3 days and were successfully extubated (extubation failure rate 10%). Due to the small number of failures ( n = 5), only descriptive analyses were performed. In successfully extubated newborns, IDT and DE increased at T2 and T3 compared to T1 ( p < 0.05), with IDT highest at T2. No significant changes were observed in EDT or DTF, which remained consistently elevated. Conclusion : In preterm newborns successfully extubated, diaphragmatic thickness and excursion increased during the SBT and remained elevated after extubation. These findings may support the use of diaphragmatic ultrasound to guide extubation readiness and monitor post-extubation adaptation in preterm infants. What is Known: • Extubation decisions in preterm infants rely mainly on clinical judgment .• Diaphragmatic ultrasound is used to assess diaphragmatic function in various neonatal clinical situations . What is New: • This study provides descriptive data on diaphragmatic function throughout the entire weaning and post-extubation process in preterm newborns undergoing a spontaneous breathing trial (SBT) .• In successfully extubated preterm newborns, diaphragmatic thickness and excursion increased during the SBT and remained elevated after extubation, suggesting that the SBT may increase respiratory effort without reliably indicating extubation readiness in this population .
Carvalho et al. (2026) studied this question.