Combined diaphragm and lung ultrasound profiling in healthy full-term neonates: A study of early postnatal function

Abstract Diaphragmatic ultrasound (DU) and lung ultrasound (LU) are increasingly applied to evaluate neonatal respiratory muscle performance and lung aeration, respectively. This prospective, observational, single-center study assessed DU of both hemi-diaphragms and lung ultrasound (LU) in healthy full-term neonates on days of life (DOL) 1 and 3 to profile postnatal physiology and establish normative values. DU metrics included diaphragmatic excursion (DE), contraction velocity (DCV), inspiratory diaphragm (DTi) and expiratory diaphragm (DTe) thickness, diaphragmatic thickening fraction (DTF), and inter-hemidiaphragm DTF difference (ΔDTF). LU was performed using a six-zone, three-point scoring system (LUS). Perinatal-neonatal characteristics were recorded. Twenty newborns (10 male, 10 female, mean gestational age 39.0±1.2 weeks, mean birth weight 3334±343 g) were evaluated, with equal distribution between vaginal and cesarean deliveries. No significant differences were observed in DE, DCV, DTi, DTe, or DTF between DOL 1 and 3. Sex had no effect on DU parameters. Cesarean-born neonates demonstrated significantly lower DE and DTF on DOL 1, but values were comparable by DOL 3. LUS was similar between DOL 1 and DOL 3 [medians (Q1–Q3): 1 (0–1.3) and 1 (0–1), respectively, p=0.244], with no differences by delivery mode or sex. Conclusion: Diaphragmatic function is stable in healthy neonates without significant pulmonary involvement on LU during the first three postnatal days. Mode of delivery influences diaphragmatic performance on DOL 1 and should be considered in early assessments. Combined DU and LU provide complementary insights into neonatal respiratory adaptation and may serve as reference values for clinical practice and research.