RDS, respiratory distress syndrome

RDS, respiratory distress syndrome, refers to a group of conditions which are all characterized by failure of normal respiration caused by lack of a substance called surfactant in the lungs. Surfactant acts as a detergent to lower the surface tension of the fluid in the air sacs (alveoli) of the lungs. Without sufficient amounts of this chemical, the surface tension in the air sacs is too high, and the air sacs tend to collapse. This reduces the surface area available for the exchange of oxygen and carbon dioxide and leads to low blood oxygen (hypoxia) and high blood carbon dioxide (hypercapnia).

In childhood, the condition is almost totally confined to premature infants, in whom it used to bear the name hyaline membrane disease. In these chldren, it is caused by the fact that until a fetus nears term gestation, surfactant is not produced in sufficient quantities to allow the lungs to inflate properly. A related type of repiratory distress syndrome may occur in children or adults who experience profound shock in the course of a severe illness or in reponse to life-threatening trauma ("shock lung").

Treatment is basically supportive, with positive pressure ventilation (respirator) required for all but the mildest cases. The lungs have the ability to recover by producing more surfactant, especially if stressed.

In the last few years, RDS has been treated as well with artificial surfactant, extracted from slaughtered cows. This has improved survival and lessened the severity of the lung disease, often dramatically.

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