The increase in diaphragm thickness in preterm infants is related to birth weight: a pilot study.

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. This prospective monocentric observational study 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 h 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). 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; and LET = 0.00004, p < 0.001. Right DTF values remained stable since birth but left DTF increased with time only in infants with BPD.   Conclusion: 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, but it does increase left DTF. What is Known: • Diaphragm 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. What is New: • Birth weight is the only variable related to diaphragm thickness in preterm infants born before 32 weeks postmenstrual age. • Days of invasive mechanical ventilation do not influence diaphragm increase in thickness in preterm infants.

Pleural line thickness reference values for preterm and term newborns.

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.