Disease, hyaline membrane: Typically a respiratory disease of the newborn, especially the premature infant, this serious condition occurs in babies who are born without lungs that are fully developed. The lungs do not fully function or inflate, making breathing very difficult if not impossible without medical intervention.
The word "hyaline" comes from the Greek word "hyalos" meaning "glass or transparent stone such as crystal." The membrane in hyaline membrane disease looks glassy.
Hyaline membrane is now commonly called respiratory distress syndrome (RDS). It is caused by a deficiency of a molecule called surfactant.
Respiratory distress syndrome almost always occurs in newborns born before 37 weeks of gestation. The more premature the baby is, the greater is the chance of developing respiratory distress syndrome . It is also more likely to occur in newborns of diabetic mothers.
Surfactant, a mixture of phospholipids and lipoproteins, is secreted by lung cells. The air-fluid interface of the film of water lining the alveoli of the lung (where the exchange of oxygen and CO2 occurs) exerts large forces that cause the alveoli to close if surfactant is deficient. Lung compliance is decreased, and the work of inflating the stiff lungs is increased. The preterm newborn is further handicapped because his or her ribs are more easily deformed (compliant). Breathing efforts therefore result in deep sternal (breastbone) retractions but poor air entry if the ribs are compliant compared with the lungs. This results in diffuse atelectasis (collapse of the lungs).
Rapid, labored, grunting respirations usually develop immediately or within a few hours after delivery, with retractions above and below the breastbone and flaring of the nostrils. The extent of atelectasis (lung collapse) and the severity of respiratory failure progressively worsen.
Not all infants with respiratory distress syndrome have signs of respiratory distress; extremely low birth weight newborns (i.e., < 1000 g) may be unable to initiate respirations at birth because their lungs are so stiff; they may fail to initiate breathing in the delivery room.
Respiratory distress syndrome can be reduced by assessment of fetal lung maturity to determine the optimal time for delivery. When a fetus must be delivered prematurely, giving betamethasone systemically to the mother for at least 24 hours before delivery induces fetal surfactant production and usually reduces respiratory distress syndrome risk or decreases its severity.
If untreated, severe respiratory distress syndrome can result in multiple organ failure and death. However, if the newborn's ventilation is adequately supported, surfactant production will begin and respiratory distress syndrome will resolve by 4 or 5 days. Recovery is hastened by treatment with pulmonary surfactant.
