Surfactant deficient lung disease (SDLD, also known as respiratory distress syndrome and previously as hyaline membrane disease) is a condition seen in premature infants. It is caused by insufficient surfactant production and structural immaturity of the lungs

Pathophysiology

Surfactant production is started by type II pneumocytes at around 32 weeks’ gestation. It is a phospholipid that lines the alveoli, decreasing alveolar surface tension, preventing alveolar collapse, and increasing lung compliance. Lack of surfactant results in the development of progressive atelectasis, intrapulmonary shunting, hypoxemia, and cyanosis. The natural course of RDS is progressive worsening of symptoms during the first 24 to 48 hours of life, followed by improvement once surfactant production reaches adequate levels, usually by 72 hours.

Risk factors

The risk of SDLD decreases with gestation

• 50% of infants born at 26-28 weeks
• 25% of infants born at 30-31 weeks

Other risk factors for SDLD include

• male sex
• diabetic mothers
• Caesarean section
• second born of premature twins

Clinical features are those common to respiratory distress in the newborn, i.e. tachypnoea, intercostal recession, expiratory grunting and cyanosis

Chest x-ray characteristically shows 'ground-glass' appearance with an indistinct heart border

Management

• prevention during pregnancy: maternal corticosteroids to induce fetal lung maturation