Lung Ultrasound and Static Lung Compliance during Postnatal Adaptation in Healthy Term Infants

B-lines in lung ultrasound can be used to estimate lung liquid. B-lines are ring-down artifacts that arise from alterations to subpleural lung parenchyma. Lung ultrasound has been used to differentiate between diseases causing respiratory symptoms in neonates. B-lines are also seen in healthy infants during postnatal adaptation. Static lung compliance is a measure of the elasticity of the lungs.

Our aim was to document lung ultrasound findings, static lung compliance and their relationship during postnatal adaptation in healthy term infants.

Lung ultrasound and measurement of static lung compliance were performed in 34 infants at ages of 0-4 and 24 h. B-lines in lung ultrasound were scored using a 5-step scale. Separate ultrasound scores for the upper and lower fields were also calculated.

A significant decrease in the abundance of B-lines and a concomitant significant improvement in static lung compliance was observed from <4 to 24 h of age. At <4 h the B-lines were significantly more abundant in the lower fields. No significant correlation existed between lung ultrasound and static lung compliance.

The concomitant decrease in the B-lines in ultrasound and the increase in lung compliance during the first 24 h are likely to reflect clearance of lung liquid.