Respiratory Distress Syndrome

Respiratory distress syndrome of the newborn, historically called hyaline membrane disease, is the acute breathing disorder of preterm infants caused by deficiency of pulmonary surfactant. Without enough surfactant to lower alveolar surface tension, the immature lung collapses with each breath, and the infant shows grunting, retractions, nasal flaring, and increasing oxygen need within hours of birth.

Definition

Respiratory distress syndrome is an acute neonatal lung disorder resulting from inadequate pulmonary surfactant, producing diffuse alveolar collapse, reduced lung compliance, and progressive hypoxemic respiratory failure, most commonly in preterm infants.

Scope

The entry covers the surfactant-deficiency mechanism of respiratory distress syndrome, its relationship to gestational age, the classic clinical and radiographic picture, and the broad lines of evidence behind antenatal steroids, surfactant, and respiratory support. It is a reference description of the disease, not a management protocol.

Core questions

• How does surfactant deficiency cause alveolar collapse and respiratory failure?
• Why does the risk of respiratory distress syndrome rise as gestational age falls?
• How do antenatal corticosteroids and exogenous surfactant alter the course of the disease?
• How does respiratory distress syndrome relate to the later development of bronchopulmonary dysplasia?

Key concepts

• Pulmonary surfactant
• Alveolar surface tension and the law of Laplace
• Lung compliance
• Type II pneumocytes
• Antenatal corticosteroids
• Exogenous surfactant replacement
• Continuous positive airway pressure (CPAP)

Mechanisms

Pulmonary surfactant, produced by type II pneumocytes, lowers surface tension at the air-liquid interface of the alveolus and keeps alveoli open at end-expiration. In the preterm lung this surfactant is deficient; high surface tension then causes widespread alveolar collapse (atelectasis), stiff non-compliant lungs, and impaired gas exchange. Avery and Mead (1959) linked the disease to surface-tension properties of the lung, establishing the surfactant-deficiency concept. The resulting hypoxemia and work of breathing produce the clinical syndrome; ventilation and oxygen used to treat it can, in turn, injure the developing lung (Northway et al., 1967).

Clinical relevance

Respiratory distress syndrome is a defining problem of preterm neonatal care and a frequent reason for respiratory support in the newborn period. This entry explains the disease for reference and learning and is not a basis for diagnosing or treating any individual infant.

Epidemiology

Incidence rises steeply with decreasing gestational age, affecting most extremely preterm infants and becoming uncommon near term. Male sex, maternal diabetes, and lack of antenatal corticosteroids are associated with higher risk, while antenatal steroids reduce both incidence and severity (Sweet et al., 2023).

Evidence & guidelines

European consensus guidelines synthesize randomized evidence on antenatal corticosteroids, exogenous surfactant, and respiratory support strategies for respiratory distress syndrome (Sweet et al., 2023). Trials such as the SUPPORT study compared early CPAP with prophylactic surfactant and supported non-invasive support as an initial strategy in many extremely preterm infants (SUPPORT Study Group, 2010). Guidance is summarized for orientation only and is not clinical direction.

History

The disorder was long known as hyaline membrane disease for the eosinophilic membranes seen in affected lungs at autopsy. Avery and Mead's 1959 demonstration that affected lungs lacked the surface-tension-lowering material identified surfactant deficiency as the cause, a discovery that led over later decades to antenatal corticosteroids and exogenous surfactant therapy and to a dramatic fall in mortality.

Debates

Early CPAP versus prophylactic surfactant as the initial approach

Whether extremely preterm infants are best started on non-invasive CPAP or given early intubation and surfactant has been tested in randomized trials; results support non-invasive support as a reasonable initial strategy for many infants, while selective surfactant remains important.

Key figures

• Mary Ellen Avery
• Jere Mead
• David Sweet

Seminal works

• avery-mead-1959
• northway-1967
• sweet-2023
• support-2010

Frequently asked questions

What causes respiratory distress syndrome in newborns?

It is caused by a deficiency of pulmonary surfactant in the immature lung, which leads to high alveolar surface tension, collapse of alveoli, stiff lungs, and impaired oxygenation, most often in infants born preterm.

Is hyaline membrane disease the same as respiratory distress syndrome?

Yes. Hyaline membrane disease is the older name, derived from the membranes seen in affected lungs; it refers to the same surfactant-deficiency disorder now usually called neonatal respiratory distress syndrome.