RESPIRATORY DISTRESS SYNDROME (RDS)

 

RESPIRATORY DISTRESS SYNDROME (RDS)

Respiratory distress syndrome previously called hyaline membrane disease is a syndrome in premature infants caused by developmental insufficiency of lung surfactant production and structural immaturity in the lungs. It can cause affected babies to need extra oxygen to help them breathing.

Respiratory distress syndrome, is a common breathing or respiratory condition that affects newborn's lungs/alveoli, basically caused by pulmonary surfactant deficiency in the lungs of the neonate, most commonly in those born at less than 37 weeks of gestation, characterized by grunting sounds with breathing, chest retractions, dyspnea and cyanosis.

Pulmonary surfactant is a mixture of phospholipids and lipoproteins secreted by type II pneumocytes. Before birth, the fetal lungs/alveoli are filled with fluid since it doesn't breath inside the uterus. At birth, lung surfactant diminishes the surface tension of water film that lines the alveoli to collapse and the work required to inflate them. Lung surfactant begins to be made in the fetus about 24-28 weeks of pregnancy and by about 35 weeks gestation, most babies have developed adequate amount of surfactant. It is released into the lungs to help open and inflate the alveoli during respiration with a low amount of force.

Respiratory distress syndrome results from deficiency in pulmonary surfactant activity due to lung immaturity. If for example birth occurs before 35 weeks of gestation, the premature infant may not be able to cope for long time as a result of immature lungs. At first, the infant may breath with minimal difficulties, initially but as the surfactant present progressively reduces, the respiration become laboured because the alveoli cannot be opened and inflated adequately. With surfactant deficiency, a greater pressure/force is needed to open the alveoli, and without adequate airway pressure, the lungs become diffusely atelectatic, triggering inflammation and pulmonary edema.

This will cause impairment in gaseous exchange resulting in low levels of oxygen in blood and accumulation of carbon dioxide resulting in blood acid level and severe hypoxia. Increased acidosis in turn leads to capillary damage and necrosis surrounding the alveoli, which again suppresses the production of surfactant with increasing atelectasis.