A baby's first breaths involve more than just getting air into the lungs, and for the first time research has identified the important role of the chest wall in this process.
Newborn lungs are full of liquid, which needs to be cleared to allow the entry of air and the beginning of gas exchange. While often overlooked, the chest wall plays a critical role in this transition to life outside the womb.
The latest Hudson Institute research, published in the Federation of American Societies for Experimental Biology journal, shows how, to accommodate both this liquid and the incoming air, the stiffness and flexibility of the chest wall have to be finely balanced.
"The chest wall must expand and, as it is highly compliant, it can easily do so," said first author, PhD student Cailin Diedericks.
"However, that reduces breathing efficiency, so the chest wall must stiffen after birth to improve breathing efficiency." she says
More than just oxygen in baby's first breath
Senior author, Professor Stuart Hooper, says the changing role of the chest wall in respiratory function after birth is largely unknown, so this review summarises its importance and how it impacts breathing at this crucial moment in life.
"At birth, the chest wall expands to accommodate both the incoming air and the liquid that is cleared into lung tissue, causing lung oedema." Prof Hooper explains.
Benefits of vaginal delivery
"Infants born by elective caesarean section near term are at higher risk of developing respiratory distress after birth than vaginally delivered infants," he said. "Our research shows that this is due to a higher level of lung oedema after birth, providing an opportunity to avoid and/or treat this condition in high-risk infants."
Approximately 7 per cent of infants born by elective caesarean section near term develop respiratory distress in the first few hours after birth.
While these otherwise healthy infants need to be admitted into intensive care, it is now clear that this is largely avoidable and that supporting the chest wall is an exciting and new non-invasive way of treating these infants.
Non-invasive neonatal treatments
Prof Hooper said that in adults, lung and chest wall compliance is approximately equal, however, in neonates, the chest wall is approximately three times more compliant than the lungs. The impact of this remains poorly understood.
Cailin Diedericks believes that improving our understanding of the chest wall's role is essential, as altering its mechanics can affect breathing efficiency shortly after birth.
"For example, swaddling, which applies external pressures of 5-10 cmH2O, compresses the chest wall and could impair respiratory function shortly after birth," she said.
"Conversely, external negative pressures (such as those applied with the iron lung during the poliomyelitis epidemic) expand the chest wall and improve respiratory function."
Better understanding of the role of the chest wall in breathing after birth could lead to alternative ways to manage conditions such as respiratory distress in newborns.
