a common complication in infants, especially in premature newborns, characterized by extremely laboured breathing, cyanosis (a bluish tinge to the skin or mucous membranes), and abnormally low levels of oxygen in the arterial blood. Before the advent of effective treatment, respiratory distress syndrome was frequently fatal. Autopsies of children who had succumbed to the disorder revealed that the air sacs (alveoli) in their lungs had collapsed and a “glassy” (hyaline) membrane had developed in the alveolar ducts.

Although respiratory distress syndrome occurs mostly in premature, low-birth-weight infants (those weighing less than 2.5 kg, or about 5.5 pounds), it also sometimes develops in full-term infants, particularly those born to diabetic mothers. The disorder arises because of a lack of surfactant; this is a pulmonary substance that prevents the alveoli from collapsing after the infant's first breaths have been taken. The syndrome was formerly the leading cause of death in premature infants, but considerable success in saving affected infants has been achieved by using mechanical ventilators that deliver air under pressure into the alveoli. The most seriously affected newborns are treated for several days with an extracorporeal membrane oxygenator, which does the work of the lungs by oxygenating the blood and removing carbon dioxide. The continual air pressure provided by the ventilator prevents the collapse of the air sacs. As the infant's lungs mature and begin to produce surfactant—usually within three to five days after birth—the child is weaned from the ventilator. Most children who survive have no aftereffects.