Clinical paperLung 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 as a diagnostic tool for evaluation of newborns with respiratory distress.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 Following birth, the organ responsible for gas exchange transitions from the placenta to the lungs.16 To establish pulmonary gas exchange, the airways must be cleared of liquid to allow the entry of air. LUS may be able to characterize this process. LUS can be performed at the bedside in real time, may be easily repeated during clinical changes and treatments, and does not expose the infant to ionizing radiation.17, 18
Ultrasound beams penetrating an unaerated, liquid-filled lung create true ultrasound images as the density of liquid changes between the tissue layers. In contrast, ultrasound beams passing through an aerated lung produce artifacts.1, 8, 19, 20 Traditionally, the interference of sound waves caused by air in the lungs has discouraged the use of LUS as a diagnostic tool. However, an understanding of these characteristic artifacts has led to the recognition that these artifacts are consistent and have diagnostic importance.1, 6, 8, 9, 12, 13, 21 Our hypothesis is that we can use lung ultrasound to describe initial lung aeration and liquid clearance as healthy term and near term infants initiate breathing after birth.
Section snippets
Methods
This was a prospective, observational study of newborn term and late preterm infants. We used ultrasound to characterize the appearance of the lungs as infants initiate breathing after birth. The study was conducted at the Royal Women’s Hospital, in Melbourne, Australia, a regional referral hospital averaging more than 7000 deliveries per year.
Results
Between April 2015 and February 2016, we attempted to capture the initiation of breathing in 76 infants. We enrolled and studied 63 infants (83% of attempted infants). We missed the initiation of breathing in 13 infants: 9 because they had taken ≥5 breaths before the chest was available to the researcher, there was a recording error in 2 infants, 1 infant did not breath initially and required positive pressure ventilation, and 1 infant because the researcher was not in the room when the infant
Discussion
This is the first study that has used ultrasound to describe the appearance of the lungs prior to the initiation of breathing, while the lung was gasless, and during the first breaths. In the 1960s, Karlberg and Lind used serial chest X-rays of infants after birth as they aerated their lungs.29, 30 More recent studies using phase contrast imaging in spontaneously breathing newborn rabbits have to demonstrate that lung aeration occurs within the first few breaths after birth.31, 32, 33 These
Conclusions
This study demonstrates that lung ultrasound can be used to observe the initiation of breathing in healthy term infants. Establishment of the pleural line, indicating lung inflation, and substantial clearance of liquid is seen during the first few breaths after birth. Studies investigating the use of lung ultrasound in the delivery room to evaluate the infant who requires respiratory support are warranted.
Conflict of interest statement
The authors confirm there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.
Information on grants that supported this research and ethics are stated below: Peter Davis (App ID#1059111) and C Omar F Kamlin (App ID#1073533) are support by an Australian National Health and Medical Research Council Practitioner and Principal Research Fellowship. Peter Davis and Stuart Hooper
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2017.02.017.