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

Diaphragmatic ultrasound (DUS) and lung ultrasound (LUS) are increasingly applied to evaluate neonatal respiratory muscle performance and lung aeration, respectively. This prospective, observational, single-center study assessed DUS of both hemi-diaphragms and LUS in healthy full-term neonates on days of life (DOL) 1 and 3 to profile postnatal physiology and establish normative values. DUS metrics included diaphragmatic excursion (DE), contraction velocity (DCV), inspiratory diaphragm (DTi) and expiratory diaphragm (DTe) thickness, diaphragmatic thickening fraction (DTF), and inter-hemi-diaphragm DTF difference (ΔDTF). A six-zone, 3-point scoring system was used to evaluate LUS aeration. Twenty newborns (gestational age 39.0 ± 1.2 weeks, birth weight 3334 ± 343 g) were evaluated. No significant differences were observed in DE, DCV, DTi, DTe, DTF, or ΔDTF between DOL 1 and 3. Sex had no effect on DUS parameters. Cesarean-born neonates demonstrated significantly lower DE and DTF on DOL 1, but values were comparable by DOL 3. LUS aeration scores were 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. Intra-observer reliability was excellent for nearly all DUS metrics on DOL 1 and DOL 3 (intraclass correlation coefficients > 0.90).

Diaphragmatic function is stable in healthy neonates without significant pulmonary involvement on LUS during the first three postnatal days. Mode of delivery appears to transiently influence diaphragmatic performance on DOL 1. Combined DUS and LUS provide complementary insights into neonatal respiratory adaptation and may serve as reference values for clinical practice and research.

• Point-of-care diaphragmatic ultrasound (DUS) and lung ultrasound (LUS) are increasingly utilized as safe, bedside tools for assessing neonatal respiratory distress and supporting clinical decision-making.

• This is the first study to evaluate both DUS and LUS together in healthy term newborns during the first 3 days of life, demonstrating stable diaphragmatic function transiently influenced by delivery mode but independent of newborn sex.