Respiratory distress syndrome
Citation, DOI & article data
Respiratory distress syndrome (RDS) is a relatively common condition that occurs in preterm neonates resulting from insufficient production of surfactant.
RDS is also known as hyaline membrane disease (not favored as reflects non-specific histological findings), neonatal respiratory distress syndrome, lung disease of prematurity (both non-specific terms), or surfactant deficiency disorder 2.
The incidence is estimated at 6 per 1000 births 2. Uncommon after 36 weeks' gestation due to development of pneumocyte surfactant production around 35 weeks 5.
Respiratory distress presents in the first few hours of life in a premature baby. Signs include tachypnea, expiratory grunting, and nasal flaring. The infant may or may not be cyanosed. Substernal and intercostal retractions may be evident.
Risk factors include maternal diabetes, greater prematurity, perinatal asphyxia, and multiple gestations.
Associated conditions are those that can occur in prematurity: germinal matrix hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, delayed developmental milestones, hypothermia, and hypoglycemia.
Immature type II pneumocytes cannot produce surfactant. The lack of surfactant increases the surface tension in alveoli causing them to collapse. Patients have a decreased lecithin to sphingomyelin ratio. Damaged cells, necrotic cells, and mucus line the alveoli.
Although most cases are related to prematurity alone, rarely patients may have genetic disorders of surfactant production and can present in a similar clinical and radiological manner 6.
As the alveoli are collapsed (microscopically), the lungs are collapsed macroscopically as well. It is a diffuse type of adhesive atelectasis.
- low lung volumes
- diffuse, bilateral and symmetrical granular opacities
- bell-shaped thorax
- air bronchograms may be evident
Hyperinflation makes the diagnosis less likely, unless the patient is intubated.
If treated with surfactant therapy, there may be an asymmetric improvement as more surfactant may reach certain parts of the lungs than others.
On transabdominal ultrasound, retrodiaphragmatic hyperechogenicity can be seen. If this hyperechogenicity does not resolve by day 9-18 on follow up ultrasound, it helps in the prediction of risk of development of bronchopulmonary dysplasia ref.
Treatment and prognosis
Exogenous surfactant administration is an effective treatment, traditionally administered via endotracheal tube, though less invasive methods of surfactant administration such as via laryngeal mask airway are becoming more common 7. Supportive oxygen therapy is typically required for a period of time.
- persistent patent ductus arteriosus (PDA) due to reduced oxygen stimulus
- pulmonary interstitial emphysema or air leak (secondary to requirement for mechanical ventilation)
- oxygen toxicity (from treatment)
- pulmonary hemorrhage
- bronchopulmonary dysplasia
- recurrent pulmonary infection
- subglottic stenosis (secondary to intubation)
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- 7. Smee N, Boyd D, Conetta H, O'Shea J. Laryngeal Mask Airway Surfactant Administration: Case Series of 60 Infants. Arch Dis Child Fetal Neonatal Ed. 2021;106(3):342. doi:10.1136/archdischild-2020-320438 - Pubmed