Lung ultrasound during the initiation of breathing in healthy term and late preterm infants immediately after birth, a prospective, observational study.

INTRODUCTION: Lung ultrasound (LUS) has shown promise for evaluation of newborns with respiratory distress. However, no study has described the appearance of LUS during the initiation of breathing. We used LUS to describe the appearance of the lungs in healthy infants immediately after birth, starting with the infant's first breath, through the first 20min after birth.

METHODS: This was a single-center observational study enrolling neonates born at ≥35 weeks. We obtained LUS video recordings with the initiation of breathing. Recordings that captured one of the 1st four breaths after birth were included. We also obtained recordings at 1-10 and 11-20min after birth. Recordings were graded using a modified version of a previously published system, with additional grades to describe the appearance of the lungs prior to establishment of the pleural line.

RESULTS: We studied 63 infants, mean gestational age=391/7 ±2 days, mean weight=3473g±422, 33 infants were delivered vaginally and 30 via cesarean section. We captured the first breath after birth in 28 infants and within the first four breaths from the remaining 35 infants. The pleural line was established by a median of 4 breaths (3-6). At the 1-10min examination, all infants had an established pleural line and 89% demonstrated substantial liquid clearance. At the 11-20min examination, all infants had substantial liquid clearance.

CONCLUSION: Establishment of the pleural line, indicating lung aeration and substantial liquid clearance is achieved with the first few breaths after birth in term and near term infants.