Scientific Evidence Is the Only Common Ground for the Debate on Neonatal Lung Ultrasound.

Abstract

Dear Editor, We read with interest the article by Drs Lavizzari and Veneroni titled “Biochemical and Lung Function Test Accuracy for Predicting the Need for Surfactant Therapy in Preterm Infants: A Systematic Review” [1]. We were stricken, however, by the following incorrect statements not supported by any literature: “Lung ultrasound score (LUS) is subject to variations in technique and interpretations, depends on the used probe, and requires specific training. LUS can assess only a portion (the more superficial one) but not the entirety of the lung and it is not a direct measure of the lung functional status.” We believe that the reader should be informed of the abundant evidence that contradicts Drs Lavizzari and Veneroni’s assertions. First, the interpretation of lung ultrasound findings in neonates and its reliability is not influenced by the type of probe [2] or the operators’ expertise [3]. Same results have been accumulated in hundreds of studies performed in adult critical care and summarized by evidence-based guidelines since 2012 [4]. Interpretation of neonatal lung ultrasound does not even change when lung ultrasound is performed in low-resource settings [5]. This is also in line with adult literature that included lung ultrasound in the diagnosis of acute respiratory distress syndrome (RDS) using the socalled Kigali definition [6]. The lung ultrasound learning curve has been extensively studied and found to be short, both in adult [7] and neonatal patients with RDS [8]. Second, the optimal depth to scan lung tissue in adult patients and still have a good correlation with CT-scan is 5 cm [9]: lung ultrasound performed with linear probes in neonates uses a depth of approximately 3–4 cm, which is adequate for the size of the newborn lung. Moreover, primary surfactant deficiency produces a homogeneous disease equally affecting deep and superficial lung parenchyma [10], so this can hardly be seen as a limitation when scanning preterm neonates. Third, stating that lung ultrasound is not a measure of lung function is also incorrect. Lung ultrasound scores measure lung aeration, i.e., the lung volume available for gas exchange and this is correlated with surfactant activity [11] and lung mechanics both in neonates and adults [12]. Lung aeration represents a direct consequence of