Pulmonary surfactant deficiency occurs in premature neonates, caused by atelectasis due to insufficient surfactant production by type II pneumocytes, which appears as diffuse bilateral granular opacities on chest radiograph.
Description
Pulmonary surfactant deficiency disease, commonly known as neonatal respiratory distress syndrome (RDS), is a condition primarily affecting preterm infants caused by insufficient production of pulmonary surfactant. Surfactant is a lipoprotein complex critical for reducing surface tension in the alveoli, preventing atelectasis, and facilitating gas exchange. The disease manifests shortly after birth, with symptoms of respiratory distress.
Pathogenesis
The pathogenesis involves inadequate production of surfactant by the immature lungs of preterm infants, leading to high alveolar surface tension, alveolar collapse, and impaired gas exchange. Surfactant synthesis and storage in type II pneumocytes typically mature by 35-36 weeks of gestation, making infants born prematurely particularly vulnerable.
Epidemiology, Risk Factors & Associations
- Incidence inversely related to gestational age and birth weight.
- Risk factors include prematurity, male sex, perinatal asphyxia, and maternal diabetes.
Clinical Features
- Tachypnoea, grunting, nasal flaring, and chest wall retraction shortly after birth (first few hours).
- Cyanosis in room air.
- Reduced breath sounds with fine crackles on auscultation.
Complications
- Chronic lung disease/bronchopulmonary dysplasia from prolonged oxygen and ventilatory support.
- Pneumothorax and other air leak syndromes due to high ventilatory pressures.
- Patent ductus arteriosus and intraventricular haemorrhage due to hypoxia and treatment interventions.
Pathological Features
Histopathology
- Macroscopic: Lungs are solid, airless, and resemble liver tissue (“liver-like lungs”).
- Microscopic: Diffuse atelectasis with hyaline membranes lining the alveoli, composed of fibrin, cellular debris, and plasma proteins.
Radiological Features
XR
- Diffuse, bilateral and symmetrical granular opacities
- Normal to low lung volume, bell-shaped thorax
- Air bronchograms may be present
Diagnosis
- Clinical presentation and chest X-ray findings in the context of prematurity are diagnostic.
- Blood gas analysis shows hypoxaemia and hypercapnia.
Differential Diagnosis
- Transient tachypnoea of the newborn: Wet lung disease, occurs in term or near-term newborn with similar symptoms but typically self-resolves within the first few days of life. Perihilar streaky interstitial oedema sometimes with pleural effusion. Lung volumes are normal or slightly hyperinflated.
- Meconium aspiration syndrome: Distinguished by the presence of meconium-stained amniotic fluid and a history of foetal distress.
- Congenital pneumonia: May present similarly but often has signs of infection such as fever and leukocytosis. Usually due to group B Streptococcus. Also has low lung volumes with granular opacities, however pleural effusions may be present. Non-group B neonatal pneumonia demonstrates more patchy asymmetric perihilar opacities, pleural effusions, and high lung volumes.
- Neonatal pulmonary haemorrhage: Sudden onset of respiratory distress with bloody tracheal aspirates.
Management
- Prophylactic administration of surfactant to high-risk preterm infants immediately after birth.
- Supportive care including oxygen therapy, mechanical ventilation if required, and management of fluid and electrolyte balance.
- Prevention strategies include maternal administration of corticosteroids before preterm delivery to enhance fetal lung maturation..