Background In lung ultrasound (LUS), the pleural line is an artifact whose thickness depends on the underlying lung pathology. To date there are no published studies on normal values of pleural line thickness (PLT) in newborns. Objective The aim of our study is to describe normal PLT values in term newborn (TN) and preterm newborn (PTN). Methods We recruited eupneic TN and PTN, under 34 weeks of gestation, on their first 24 hours of life. Newborns presenting any respiratory distress since birth were excluded. LUS was performed in four areas: upper anterior, lower anterior, lateral and posterior. At each location, we measured PLT and values where compared. Intraobserver and interobserver agreement were assessed using the intraclass correlation coefficient (ICC), and the kappa coefficient. Results We included 23 TN with a median birth weight of 3365 g (interquartile range [IQR] 3100‐3575 g) and a median gestational age of 39 weeks (IQR, 38‐40 weeks). In the PTN group, 23 patients were included with a median birth weight of 1350 g (IQR, 1150‐1590 g) and a median gestational age of 31 weeks (IQR, 30‐32 weeks). Median PLT values were less than 1 mm, and there were no significant differences between groups at any locations, with the exception of the left lower anterior field (0.79 mm [IQR, 0.72‐0.89 mm] vs 0.68 mm [IQR, 0.62‐0.72 mm]). Intraobserver agreement was high: consistency ICC 0.77 (95% confidence interval [CI], 0.32‐0.92) and absolute ICC 0.78 (95% CI, 0.34‐0.93). Interobserver agreement was high for the definition of thin pleural line as less than 1 mm. Conclusions TN and asymptomatic PTN have similar PLT values. Overall, PLT in healthy newborns should be less than 1 mm.

Purpose Diaphragm ultrasound (DU) has been used in adult and pediatric critical patients in relation to prediction of extubation success or to detect diaphragm dysfunction, but there is a lack of evidence in neonates. Our aim is to study the evolution of diaphragm thickness in preterm infants, as well as related variables. Methods Prospective monocentric observational study that included preterm infants born before 32 weeks (PT32). We performed DU to measure right and left inspiratory and expiratory thickness (RIT, LIT, RET and LET) and calculated the diaphragm-thickening fraction (DTF) in the first 24 hours of life and then weekly until 36 weeks postmenstrual age, death, or discharge. Using multilevel mixed-effect regression, we evaluated the influence of time since birth on diaphragm measurements, as well as bronchopulmonary dysplasia (BPD), birth weight (BW) and days of invasive mechanical ventilation (IMV). Results We included 107 infants, and we performed 519 DUs. All diaphragm thickness increased with time since birth, but the only additional variable that influenced this growth was BW: beta coefficients RIT=0.00006; RET=0.00005; LIT=0.00005; LET=0.00004, p<0.001. Right DTF values remained stable since birth. Conclusions In our population we found that the higher the BW, the higher diaphragm thicknesses at birth and follow-up. Contrary to the previously published findings in adult and pediatric settings, we were unable to describe a relationship between days of IMV and diaphragm thickness in PT32. The final diagnosis of BPD does not influence this increase either.

PurposeDiaphragm ultrasound (DU) has been used in adult and pediatric critical patients in relation to prediction of extubation success or to detect diaphragm dysfunction, but there is a lack of evidence in neonates. Our aim is to study the evolution of diaphragm thickness in preterm infants, as well as related variables. MethodsProspective monocentric observational study that included preterm infants born before 32 weeks (PT32).We performed DU to measure right and left inspiratory and expiratory thickness (RIT, LIT, RET and LET) and calculated the diaphragm-thickening fraction (DTF) in the rst 24 hours of life and then weekly until 36 weeks postmenstrual age, death, or discharge. Using multilevel mixed-effect regression, we evaluated the in uence of time since birth on diaphragm measurements, as well as bronchopulmonary dysplasia (BPD), birth weight (BW) and days of invasive mechanical ventilation (IMV). ResultsWe included 107 infants, and we performed 519 DUs. All diaphragm thickness increased with time since birth, but the only additional variable that in uenced this growth was BW: beta coe cients RIT=0.00006; RET=0.00005; LIT=0.00005; LET=0.00004, p<0.001. Right DTF values remained stable since birth. ConclusionsIn our population we found that the higher the BW, the higher diaphragm thicknesses at birth and followup. Contrary to the previously published ndings in adult and pediatric settings, we were unable to describe a relationship between days of IMV and diaphragm thickness in PT32. The nal diagnosis of BPD does not in uence this increase either. What Is KnownDiaphragm thickness and diaphragm thickening fraction have been related to the time on invasive mechanical ventilation in adults and pediatric patients, as well as with extubation failure.Very few evidence is yet available on the use of diaphragmatic ultrasound in preterm infants.

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