Respiratory distress syndrome (hyaline membrane disease) is a breathing disorder of premature newborns in which the air sacs (alveoli) in a newborn's lungs do not remain open because the production of a substance that coats the alveoli (surfactant) is absent or insufficient.
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 and allows the air sacs to remain open throughout the respiratory cycle. Usually, production of surfactant begins after about 32 weeks of pregnancy. 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 and is more common among newborns whose mother has diabetes. Rarely, the syndrome is inherited.
Symptoms and Diagnosis
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 respiratory distress occurs. Respiratory distress is manifested by visibly labored breathing, including retractions of the chest below the rib cage, flaring of the nostrils during breathing in, and grunting while breathing out. Because much of the lung is airless, newborns have low levels of oxygen in the blood, which cause a bluish discoloration to the skin (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. Eventually, without treatment, newborns may have damage to the brain and other organs from a lack of oxygen or may die.
Diagnosis of respiratory distress syndrome is based on the symptoms, levels of oxygen in the blood, and abnormal chest x-ray results.
Prevention and Treatment
The risk of respiratory distress syndrome is greatly reduced if delivery can be 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 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, newborns with mild respiratory distress syndrome may require only supplemental oxygen. The oxygen is given through prongs placed in the newborn's nostrils or through a small plastic hood (oxygen hood) filled with oxygen, which is placed over the head. Newborns with severe respiratory distress syndrome may require oxygen delivered by continuous positive airway pressure (CPAP)—a technique that allows newborns to breathe on their own while being given slightly pressurized oxygen or air given through prongs placed in both nostrils. In newborns with severe respiratory distress syndrome, a tube (endotracheal tube) may need to be passed into the windpipe (intubation), and the newborn's breathing may need to be supported with mechanical ventilation.
Use of a surfactant preparation can be lifesaving and reduces complications, such as rupture of the lungs (pneumothorax). The surfactant preparation acts in the same way that natural surfactant does. Surfactant can be given through an endotracheal tube and may be given immediately after birth in the delivery room to attempt to prevent respiratory distress syndrome before symptoms develop or in the early hours after birth to premature newborns who already have symptoms of this disorder.
Surfactant treatments may be repeated several times during the first days until respiratory distress syndrome resolves.
Last full review/revision February 2009 by Arthur E. Kopelman, MD