Surfactant is a substance that develops in the lungs and helps keep them open. If a baby is born prematurely they may not have developed surfactant and are considered to have respiratory distress syndrome or RDS.
Normally, when the lungs initially inflate with the baby’s first breath, the air sacs called alveoli expand, fill with air, and remain open. Because the sacs remain open, the surface area within the lungs becomes quite large. Imagine the difference between a straight skirt and a heavily pleated skirt. The skirt with the pleats has much more material in it and therefore a larger area that is exposed to the air. In the lungs, the air sacs, or alveoli, though more like bubbles than pleats, increase the surface area of the inside of the lungs and therefore make gas exchange easier. The larger the surface exposed to the air coming into the lungs, the more opportunity oxygen has to pass from the alveoli into the blood.
How surfactant works
A substance called surfactant is an essential part of the process allowing alveoli to remain open. Surfactant is a kind of foamy, fatty liquid that acts like grease. Without it, the air sacs open but have difficulty remaining open because they stick together. Surfactant allows the sacs to remain open.
Surfactant usually appears in the fetus’s lungs at about the 24th week of pregnancy and gradually builds up to its full level by the 37th week. Additionally, when labour begins, the mother’s body produces a type of natural steroid that makes its way to the baby through the placenta and umbilical cord. This steroid initiates or speeds up production of surfactant in the lungs in preparation for a baby’s first breath. Babies born without enough surfactant are said to have respiratory distress syndrome or RDS.
Sometimes a premature birth is not a completely unexpected event. Perhaps due to some kind of maternal or fetal problem or both, a decision is made to initiate labour or perform a caesarean section before term. In these cases, the mother will likely be given steroids to help the baby speed up production of surfactant in the lung and reduce the chances of developing RDS. At other times, a premature birth is completely unexpected and the administration of steroids either is not possible or will not have time to have an effect on the baby’s lungs by the time of birth. In this case, the baby may be given artificial or natural surfactant to take the place of what their lungs would normally produce. Surfactant replacement therapy, as it is called, acts to keep the alveoli from sticking together in the same way as naturally produced surfactant does. In either case, the baby’s breathing will usually need to be stabilized, either with supplemental oxygen or some form of ventilation that assists the baby with their breathing.
Once these measures have been taken, RDS needs time to resolve. The overwhelming majority of premature babies recover from RDS without major complications or adverse effects as the child grows older. However, newborns with severe cases of RDS, usually the smallest and most premature babies, are at risk for breathing difficulties, including chronic lung disease and respiratory infections.
More information
- Diagnosis of Respiratory Distress Syndrome
- Treatment of Respiratory Distress Syndrome