Serial Lung Ultrasound for the Evaluation of Gravity-Induced Lung Injuries in Very Preterm Infants

Background: Gravity affects the distribution of lung injuries due to gravity-induced nonhomogeneous ventilation leading to lung collapse and subsequently non-uniform lung lesions. Moreover, lung injury gradients gradually develop over time. However, changes in injury distribution after birth have not been investigated in very preterm infants. Methods: Preterm infants of less than 32 weeks’ gestational age were included in this prospective observational study. Gravity-dependent lungs (DL) were defined as dorsal lungs in a supine position or ventral lungs in a prone position, and non-dependent lungs (NDL) were defined as ventral lungs in a supine position or dorsal lungs in a prone position. Infants were assessed using lung ultrasound (LUS), which was performed on days 7, 14, 21, and 28 post-birth. Each anterior and posterior lung was scanned and received an LUS score of 0–3 points. LUS scores of the DL and NDL were compared. Total LUS scores were provided using a 0–6 point scale, which was obtained by adding the scores for each region of each lung. Results: Eighty–eight patients were enrolled in this study. On days 7, 14, and 21, LUS scores between the DL and NDL groups were significantly different (day 7, P = 0.01; day 14, P < 0.001; and day 21, P = 0.003). However, on day 28, there was no significant difference between groups (P = 0.064). Conclusions: LUS can be used to detect gravity-induced lung injury gradients in very preterm infants. Moreover, LUS revealed a trend of gradient improvement over time.