Reproducibility and reference values of diaphragmatic shortening fraction for term and premature infants

Abstract

BackgroundNew ultrasound measurements to diagnose diaphragmatic dysfunction, including diaphragmatic shortening fraction (DSF), have been studied in adults and children, but there are no data on reference values for neonates.ObjectiveTo describe DSF reference values for term neonate (TN) and preterm neonate (PTN), and to calculate its reproducibility.MethodsWe included asymptomatic TN and PTN during their first 24 hours of life. We measured DSF at the zone of apposition in both hemithoraces. Reproducibility of image acquisition, including inter‐ and intra‐rater agreement of the measurements were calculated among an experienced and a novel operator (after completion of a 1‐day course on lung ultrasound [LU] and performance of 10 diaphragm ultrasounds [DUs] under supervision), and a more‐trained examiner (completion of a 1‐day course on LU and performance of 60 DUs under supervision).ResultsTwo groups of 33 TN and 33 PTN were studied. Median DSF values did not differ between the groups, although diaphragm thickness was higher in the TN group. Intra‐observer reproducibility: the intraclass correlation coefficient (ICC) was 0.95 (95% confidence interval [95% CI] 0.86‐0.98). Interobserver reproducibility with novel operator had an ICC of 0.42 (95% CI −0.74 to 0.81), and with a more experienced operator improved to 0.76 (95% CI 0.27‐0.92). Both intra‐ and interobserver agreement were high.ConclusionsAsymptomatic TN and PTN have similar DSF values in the first 24 hours of life. The intra‐ and interobserver agreement is high. Reproducibility is acceptable, but intensive training is necessary to perform adequate DU.

Lung ultrasound for early surfactant treatment: Development and validation of a predictive model

“…Despite very few studies have evaluated the diaphragmatic function in VPI on noninvasive ventilation, the diaphragmatic measurements found in our study are consistent with the previous publications 28–30 . We also found a significant positive correlation between diaphragmatic thickness and anthropometric data as reported, 31 but we did not find association between DTF and MAP, LUS score, SF ratio, or need for surfactant treatment when assessed in the first 2 h of life and after caffeine administration.…”

“…25 , and yet may be very useful in other settings as reported by Nanda et al 27 Despite very few studies have evaluated the diaphragmatic function in VPI on noninvasive ventilation, the diaphragmatic measurements found in our study are consistent with the previous publications. [28][29][30] We also found a significant positive correlation between diaphragmatic thickness and anthropometric data as reported, 31 Optimizing antenatal care, avoiding intubation in delivery room, caffeine and early surfactant with a less invasive technique when needed, are proven strategies or "bundles" to reduce BPD. 5,37 Categorizing a continuous variable leads to loss of information and can reduce the validity of the conclusions derived from a single study.…”

“…LUS score is useful in RDS because its homogenous pattern, but in cases with coexisting conditions such as pneumothorax it cannot be considered. We also acknowledge some limitations to thickness and thickening fraction measurements because they can be difficult to assess in VPI with respiratory distress and high respiratory rates and the reproducibility may be poor in not skilled neonatologists 30 …”

“…Multivariable prediction models for surfactant administration in VPI on noninvasive ventilation for RDS VPI with respiratory distress and high respiratory rates and the reproducibility may be poor in not skilled neonatologists 30. LUS can optimize the timing of surfactant administration as reported in the ESTER study 35.…”

Reply to the correspondence letter by Alonso-Ojembarrena, Almudena and Oulego-Erroz, Ignacio: How to improve precision and reliability of diaphragm ultrasonographic measurements in newborns

“…In regard to sonographic assessment; we agree with Dr. Alonso-Ojembarrena and Dr. Oulego-Erroz that appositional view is more accurate in measuring diaphragmatic thickness and diaphragmatic thickening fraction (DTF) compared to the subcostal view. However, the main difference between our study and the previous studies on preterm infants which were cited by Dr. Alonso-Ojembarrena and Dr. Oulego-Erroz in their letter [1][2][3] is that all previous studies were done on stable infants who were not mechanically ventilated or exposed to positive pressure ventilation compared to our cohort of preterm infants who were all mechanically ventilated. As we previously mentioned in our manuscript, mechanical ventilation triggers ventilator-induced diaphragmatic dysfunction (VIDD) through myofibrillar contractile dysfunction and myofilament protein loss of the diaphragmatic muscles which later results in loss of diaphragmatic thickness, forcegenerating capacity, poor activity, and unloading of the diaphragm [4].…”