Respiratory Distress Syndrome in Newborns
(Hyaline Membrane Disease)
Premature newborns and newborns whose mother had diabetes while pregnant are at increased risk of developing respiratory distress syndrome.
Affected infants have severe difficulty breathing and may appear blue because of a lack of oxygen in the blood.
The diagnosis is based on presence of breathing trouble, oxygen levels in the blood, and chest x-ray results.
If low oxygen levels in the blood cannot be improved with treatment, the syndrome may cause brain damage or death.
If the fetus will be born prematurely, the mother may be given a corticosteroid by injection to speed up the fetus’s production of surfactant.
Oxygen is given, continuous positive airway pressure can be used to keep the air sacs open, and a ventilator may be necessary if breathing becomes too difficult for the newborn.
Treatment with synthetic surfactant given into the newborn’s windpipe can provide the surfactant that is missing until newborns start producing enough of their own surfactant.
(See also Overview of General Problems in Newborns.)
Respiratory distress is trouble breathing. For newborns to be able to breathe easily, the air sacs (alveoli) in the lungs must be able to remain open and filled with air. Normally, the lungs produce a substance called surfactant. Surfactant coats the surface of the air sacs, where it lowers the surface tension. Low surface tension allows the air sacs to remain open throughout the respiratory cycle.
Usually, the fetus begins producing surfactant at around 24 weeks of pregnancy. By between 34 weeks and 36 weeks of pregnancy, there is enough surfactant in the fetus' lungs to allow the air sacs to remain open. Thus, the more premature the newborn, the less surfactant is available, and the greater the likelihood that respiratory distress syndrome will develop after birth. Respiratory distress syndrome occurs almost exclusively in premature newborns but may also occur in full-term and near full-term newborns whose mother had diabetes while pregnant.
Other risk factors include multiple fetuses (such as twins, triplets, or quadruplets) and being a white male.
Rarely, this syndrome is caused by a mutation in certain genes that causes a deficiency of surfactant. This genetically caused type of respiratory distress syndrome may occur in full-term babies as well.
In affected newborns, the lungs are stiff and the air sacs tend to collapse completely, emptying the lungs of air. In some very premature newborns, the lungs may be so stiff that the newborns are unable to begin breathing at birth. More commonly, newborns try to breathe, but because the lungs are so stiff, severe trouble breathing (respiratory distress) occurs. Symptoms of respiratory distress include
Because much of the lung is airless in this condition, newborns with respiratory distress syndrome have low levels of oxygen in the blood, which causes a bluish discoloration to the skin and/or lips (cyanosis). Over a period of hours, the respiratory distress tends to become more severe as the muscles used for breathing tire, the small amount of surfactant in the lungs is used up, and increasing numbers of air sacs collapse. If the low oxygen levels are not treated, newborns may have damage to their brain and other organs and may die.
The diagnosis of respiratory distress syndrome is based on signs of respiratory distress, levels of oxygen in the blood, and abnormal chest x-ray results.
Respiratory distress syndrome can sometimes accompany a disorder, such as infection in the blood (sepsis) or transient tachypnea of the newborn. Therefore, doctors may do other tests to rule out these disorders. Cultures of blood and sometimes cerebrospinal fluid may be done to look for certain kinds of infections.
With treatment, most newborns survive. Natural production of surfactant increases after birth. With continued production of surfactant and sometimes with breathing support and synthetic surfactant therapy (see Treatment below), respiratory distress syndrome usually resolves within 4 or 5 days.
Without treatment that increases blood oxygen levels, newborns may develop heart failure and have damage to the brain or other organs or may die. Some infants who need treatment for a long time go on to develop bronchopulmonary dysplasia.
Before birth, doctors are able to test the maturity of the fetus's lungs by measuring the level of surfactant in the amniotic fluid. Amniotic fluid is collected from the sac surrounding the fetus during a procedure called amniocentesis or is collected from the mother's vagina (if the membranes have ruptured). The surfactant level helps doctors determine the best time to deliver the fetus. The risk of respiratory distress syndrome is greatly reduced if delivery can be safely delayed until the fetus’s lungs have produced sufficient surfactant.
When premature birth cannot be avoided, obstetricians may give the mother injections of a corticosteroid (betamethasone). The corticosteroid goes into the fetus and accelerates the production of surfactant. Within 48 hours after the injections are started, the fetal lungs may mature to the point that respiratory distress syndrome is less likely to develop after delivery or, if it does develop, is likely to be milder.
After delivery, doctors may give a synthetic surfactant preparation to newborns who are at high risk of developing respiratory distress syndrome. At-risk newborns are those who were delivered before 30 weeks of gestational age, especially those whose mother did not receive corticosteroids. The surfactant preparation can be lifesaving and reduces the risk of some complications, such as collapse of the lung (pneumothorax in the newborn). The surfactant preparation acts in the same way that natural surfactant does. Surfactant therapy can be given to the newborn through a tube placed in the mouth that leads to the windpipe (called endotracheal intubation) and may be given immediately after birth in the delivery room to attempt to prevent respiratory distress syndrome before symptoms develop.
In some newborns with respiratory distress syndrome, a breathing tube may need to be passed into the windpipe after delivery. The tube is attached to a ventilator (a machine that helps air get in and out of the lungs) to support the newborn’s breathing. Synthetic surfactant is given to the newborn through the endotracheal tube. Several doses of the synthetic surfactant may be needed.
After delivery, less premature newborns and newborns with mild respiratory distress syndrome may require only supplemental oxygen or may require oxygen delivered by continuous positive airway pressure (CPAP). Supplemental oxygen is given through prongs placed in the newborn’s nostrils. CPAP allows newborns to breathe on their own while being given slightly pressurized oxygen.
Surfactant treatments may be repeated several times during the first days of life if respiratory distress continues.