Neonatal respiratory distress syndrome (RDS) is a breathing problem that develops in babies born prematurely. RDS can also be caused by factors other than premature birth, such as infections and insufficient oxygen in the blood.
Although the lungs start developing when a baby has been in the womb for about one month, they take longer to develop than most other vital organs - in fact, more than half the pregnancy. When babies have been in the womb for 26 to 28 weeks, their lungs have the structure needed for breathing. However, they are still missing a vital component, a substance known as surfactant.
Surfactant is a chemical produced by certain lung cells. It acts like a lubricant for the smallest part of the airways, called the alveoli. Each time a person exhales, the alveoli collapse. They open again when the person breathes in. The surfactant allows the alveoli to open easily. Otherwise, a large amount of friction would be created with each breath.
RDS occurs when there is not enough surfactant in the lungs. This causes the alveoli to collapse and makes it difficult for them to open again. The collapse of the alveoli is called atelectasis. Premature babies have a hard time building up enough air pressure to open the collapsed alveoli. This makes it difficult for them to breathe.
Surfactant does not usually start being made until a baby has been in the womb for 32 to 34 weeks. About half of babies born before 32 weeks develop RDS. In general, the earlier a baby is born, the less surfactant there is in the lungs and the more trouble the baby has breathing. After the 34th week, the level of surfactant is high enough to show up in the amniotic fluid that surrounds the baby in the womb.
During the first 72 hours after birth, babies with RDS have increasing trouble breathing. In addition, the amount of oxygen in their bloodstream decreases. Some infants stop breathing when they become too tired out from the effort of trying to force air into the collapsed alveoli. If this lasts for more than 20 seconds, it is called apnea. Other symptoms include: flaring of the nostrilsa whining, moaning sound during breathing called gruntingretractions. This is a sinking in of muscles around the ribs and in the neck that occurs when considerable effort is needed to breathe.breathing that is faster than normalbluish skin color called cyanosis. This occurs when a person cannot get enough oxygen into the bloodstream. It can result from difficulty breathing.
Factors that increase a baby's risk of RDS include: premature birth having a mother who has had a previous premature baby with RDShaving a mother with diabeteshaving low body temperaturebeing malegetting insufficient oxygen at birth, called asphyxiabeing of African descentbeing delivered by cesarean section without going through laborbeing born a second twin
A key component in preventing RDS is to prevent the premature birth of a baby. Preventing the infant from becoming stressed at birth due to being cold or not getting enough oxygen can also decrease the risk of developing RDS. This can also reduce the severity of the condition if it does occur.
If premature birth is unavoidable, the mother can be given steroid medications 48 hours before delivery. This medication can stimulate the baby's lungs to produce surfactant. This therapy is most effective between 28 and 32 weeks of pregnancy. After birth, premature babies and other high-risk infants are sometimes given a dose of surfactant directly into the lungs through a breathing tube known as an endotracheal tube. This can sometimes prevent RDS from developing or decrease its severity.
During the first 72 hours, infants that are developing RDS have increasing difficulty breathing. They also have trouble getting sufficient oxygen into the bloodstream because their lungs are not functioning well. Healthcare professionals can use x-rays to help determine whether a baby is developing RDS and how severe it is. Atelectasis, the collapse of the alveoli, can be seen on a chest x-ray.
One of the long-term effects of this condition is a disease called bronchopulmonary dysplasia (BPD). If the RDS does not resolve after 2 weeks and the baby still needs to use a ventilator and oxygen by 1 month of age, then he or she is likely to develop BPD. Babies with BPD may need a machine to help them breathe for months. They also may need oxygen at home.
These infants are also subject to developing certain types of heart problems. Another potential problem for this condition is that one of the passages between blood vessels that normally close at birth may not close completely in RDS. This defect can cause abnormal blood flow.
In addition, the baby's lungs can fill up with fluid as a result or the infant's heart may fail as the result of this defect. Babies can also develop trouble with their vision because of the high levels of supplemental oxygen that they need. High levels of oxygen can make blood vessels in babies' eyes develop abnormally. This can lead to blindness.
RDS is not contagious and poses no risk to others.
Treatment of RDS depends on the severity of the condition. In some cases, the baby will recover quickly after being given surfactant at birth. In other cases, a ventilator that opens up the alveoli mechanically is needed to help the baby recover from RDS. Oxygen therapy can help the baby maintain adequate levels of oxygen in the blood stream. This is essential for the proper functioning of the infant's internal organs.
Aside from the long-term effects listed above, the side effects of respiratory distress syndrome are similar to the side effects seen in other premature babies. Babies with RDS may require antibiotics for treatment of serious bacterial infections. Certain types of antibiotics can cause hearing loss. Allergic reactions to antibiotics are rare in babies.
Many babies with RDS need to have an intravenous catheter placed into a blood vessel so that fluids, antibiotics and nutrients can be given to them while they are ill. Occasionally, one of these tubes can puncture, or cause a blood clot in, the vessel into which it was inserted. Bleeding or leakage of IV fluids into the tissues can cause severe complications, depending on where the catheter was inserted.
Many babies will go home after treatment without many problems. Some babies will need to have oxygen therapy at home. They also may need to have certain medications that help control the amount of fluid that is in their bodies. Sometimes infants will need a ventilator to help them breathe at home, as well.
If a baby develops bronchopulmonary dysplasia because of the RDS, he or she will be followed closely by a lung specialist as well as by the pediatrician. Monitoring of the other complications of RDS will depend on how severe they are. Premature babies may need a team of health care professionals to monitor several aspects of development.
Nelson's Essentials of Pediatrics, Behrman and Kleigman, 2nd edition, 1994.