| Discussion: |
Surfactant deficiency is an expression of biochemical immaturity that leads to alveolar collapse and hypoxia. The term RDS (respiratory distress syndrome) has been used to describe the clinical expression of surfactant deficiency: alveolar instability and collapse, decreased functional residual capacity, uneven air expansion, increased capillary permeability, alveolar edema, and focal pulmonary hemorrhage. However, the term respiratory distress syndrome is nonspecific and imprecise. HMD (hyaline membrane disease) has also been used to describe the histologic counterpart to RDS. However, these membranes are the result and not the cause of the disease, so again, the name is limited. Surfactant deficiency disorder has recently been proposed as a more accurate term to describe the disease entity.
Approximately 50% of neonates born between 26-28 weeks and 20-30% of neonates born at 30-31 weeks of gestation develop lung disease due to surfactant deficiency. The disease is more severe and more common in males, and occurs more commonly in whites than blacks.
Within 24-48 hours of exogenous surfactant administration, rapid uniform clearing of granular opacities is often seen. Maldistribution results in heterogeneous clearing.