Diaphragm ultrasound parameters and rapid shallow breathing index for predicting weaning failure in mechanically ventilated infants: a prospective observational PICU study

Weaning from mechanical ventilation in infants admitted to the pediatric intensive care unit remains a challenging clinical decision. Premature extubation may lead to respiratory failure and reintubation, whereas delayed weaning may prolong exposure to invasive ventilation and its complications. Bedside transthoracic ultrasound may provide an objective assessment of diaphragmatic function during spontaneous breathing trials. This study aimed to evaluate the value of diaphragm ultrasound-derived parameters and the rapid shallow breathing index in predicting weaning failure among mechanically ventilated infants in the PICU. This prospective observational study included 40 mechanically ventilated infants aged 28 days to 12 months who were admitted to the PICU of Minia University Children and Maternity Hospital between January 2024 and January 2025 and were considered ready for weaning assessment. Diaphragmatic thickness at inspiration, diaphragmatic thickness at expiration, diaphragm thickening fraction, inferior vena cava diameter, contractility, and rapid shallow breathing index were assessed during the spontaneous breathing trial. The primary outcome was weaning failure, defined as the requirement for post-extubation noninvasive ventilation or reintubation within 24-72 h after extubation. Successful weaning occurred in 34 infants (85.0%) and weaning failure in 6 (15.0%). Infants with weaning failure had significantly lower diaphragmatic thickness at inspiration [1.65 (1.61-1.66 mm) vs. 1.83 (1.79-1.92 mm), P < 0.001] and lower diaphragm thickening fraction [12.0 (11.3-13.5%) vs. 26.0 (23.0-28.0%), P < 0.001] than successfully weaned infants. RSBI was significantly higher in the weaning failure group [9.0 (9.0-9.8) vs. 7.0 (6.0-7.0), P < 0.001]. Diaphragmatic thickness at expiration, inferior vena cava diameter, and contractility did not differ significantly between groups. In this small cohort with only six weaning failure events, apparent ROC AUCs were 0.998 for diaphragmatic thickness at inspiration and 1.000 for both diaphragm thickening fraction and RSBI. After leave-one-out cross-validation of the sample-derived cutoffs, sensitivity/specificity was 83.3%/97.1% for diaphragmatic thickness at inspiration, 83.3%/100.0% for diaphragm thickening fraction, and 100.0%/100.0% for RSBI. CONCLUSION: In this small single-center cohort with only six weaning failure events, lower diaphragm thickening fraction and diaphragmatic thickness at inspiration, together with higher RSBI, were strongly associated with weaning failure. These findings and the sample-derived cutoffs should be considered exploratory and require external validation in larger multicenter cohorts before routine clinical application. WHAT IS KNOWN: • Weaning mechanically ventilated infants is challenging, and failed or delayed extubation may increase morbidity. • Diaphragm ultrasound and RSBI may support weaning assessment, but infant-specific evidence remains limited. WHAT IS NEW: • Lower inspiratory diaphragm thickness, lower diaphragm thickening fraction, and higher RSBI were associated with weaning failure. • Leave-one-out validation retained 100% sensitivity and specificity for RSBI but reduced sensitivity to 83.3% for diaphragmatic thickness at inspiration and diaphragm thickening fraction, underscoring the need for external validation.