Respiratory distress syndrome
Updates to Article Attributes
Respiratory distress syndrome (RDS) is a relatively common condition resulting from insufficient production of surfactant that occurs in preterm neonates.
On imaging, the condition generally presents as bilateral and relatively symmetric diffuse ground glass lungs with low volumes and a bell-shaped thorax.
Terminology
RDS is also known as hyaline membrane disease (not favoured as reflects non-specific histological findings), neonatal respiratory distress syndrome, lung disease of prematurity (both non-specific terms),or as some authors prefer surfactant-deficiency disorder 2.
Epidemiology
The incidence is estimated at 6 per 1000 births 2. Uncommon after 36 weeks' gestation due to development of pneumocyte surfactant production around 35 weeks5.
Clinical presentation
Respiratory distress presents in the first few hours of life in a premature baby. Signs include tachypnoea, 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 abnormalities are those that can occur in prematurity: germinal matrix haemorrhage, necrotising enterocolitis, patent ductus arteriosus, delayed developmental milestones, hypothermia and hypoglycaemia.
Pathology
Immature type II pneumocytes cannot produce surfactant. The lack of surfactant increases the surface tension in alveoli causing 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.
Radiographic features
Plain radiograph
-
Lowlow lung volumes is mandatory (atelectasis - lung collapse). -
Diffusediffuse granular oppacities (ground glass), bilateral and symmetrical - "white lungs". -
Airair bronchograms may be evident. -
Bellbell-shaped thorax. -
Hyperinflationhyperinflation (in a non-ventilated patient) excludes the diagnosis; if the patient is intubated there might be hyperinflation.
RDS can be safely excluded if the neonate has a normal chest radiograph at six hours after birth.
If treated with surfactant therapy, there may be asymmetric improvement.
Treatment and prognosis
Exogenous surfactant administration. Supportive oxygen therapy.
Complications
Acute
- persistent patent ductus arteriosus (PDA) due to reduced oxygen stimulus
- pulmonary interstitial emphysema (from treatment)
- oxygen toxicity (from treatment)
- pulmonary haemorrhage (can also be included in the differential diagnosis)
- air leak (barotrauma related to ventilation)
Chronic
- bronchopulmonary dysplasia
- recurrent pulmonary infection
- subglottic stenosis (from intubation)
Differential diagnosis
Consider:
- congenital heart disease
- group B Streptococcal pneumonia
- pulmonary haemorrhage
- pulmonary oedema / pulmonary venous congestion
- neonatal pneumonia
- transient tachypnea of the newborn: lung volumes are normal to slightly hyperinflated in TTN and decreased in RDS
-<li>Low lung volumes is mandatory (atelectasis - lung collapse).</li>-<li>Diffuse granular oppacities (ground glass), bilateral and symmetrical - "white lungs".</li>-<li>Air bronchograms may be evident.</li>-<li>Bell-shaped thorax.</li>-<li>Hyperinflation (in a non-ventilated patient) excludes the diagnosis; if the patient is intubated there might be hyperinflation.</li>-</ul><p>RDS can be safely excluded if the neonate has a normal chest radiograph at six hours after birth. </p><p>If treated with surfactant therapy there may be asymmetric improvement.</p><h4>Treatment and prognosis</h4><p>Exogenous surfactant administration. Supportive oxygen therapy.</p><h5>Complications</h5><h6>Acute</h6><ul>- +<li>low lung volumes is mandatory (atelectasis - lung collapse).</li>
- +<li>diffuse granular oppacities (ground glass), bilateral and symmetrical - "white lungs".</li>
- +<li>air bronchograms may be evident.</li>
- +<li>bell-shaped thorax.</li>
- +<li>hyperinflation (in a non-ventilated patient) excludes the diagnosis; if the patient is intubated there might be hyperinflation.</li>
- +</ul><p>RDS can be safely excluded if the neonate has a normal chest radiograph at six hours after birth. </p><p>If treated with surfactant therapy, there may be asymmetric improvement.</p><h4>Treatment and prognosis</h4><p>Exogenous surfactant administration. Supportive oxygen therapy.</p><h5>Complications</h5><h6>Acute</h6><ul>
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